Aesthetics in interactive products:Correlates and consequences of beauty

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Aesthetics in interactive products:

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Correlates and consequences of beauty

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Marc Hassenzahl, University of Koblenz-Landau

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Hassenzahl, M. (2008). Aesthetics in interactive products: Correlates and consequences

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of beauty. In Schifferstein, H. N. and Hekkert, P., editors, Product Experience, chapter 11,

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pages 287-302. Elsevier.

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Marc Hassenzahl, User Experience and Ergonomics, Design

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Folkwang University of Arts

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www.marc-hassenzahl.de

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1 Introduction

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Beauty matters. Certainly, most people would agree. Beauty is an important ingredient

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of our daily lives. We admire and praise the beauty of nature, architecture, music, other people

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– an ugly color or an awkward form easily repels us. Given its pervasiveness, the lack of

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research addressing beauty (or aesthetics) in Human-Computer Interaction (HCI) is striking

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(see Tractinsky, 2005). HCI seems a "science of design" (Carroll, 1997) that long neglected

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beauty. A cursory search of the keyword "aesthetics" in the Association of Computing

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Machinery's (ACM) Digital Library (www.acm.org/dl), for example, showed 25% of all

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retrieved papers to be published in 2005. This is so far, the culmination of a growing interest in

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the topic, which had its starting point about 10 years ago.

In an attempt to define criteria for the ACM interaction design award, Alben (1996)

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emphasized the importance of aesthetics by making it one out of eight aspects contributing to a

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quality user experience. Today, aesthetics are viewed as a non-instrumental quality, forming an

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important aspect of product appeal and experience (e.g., Hassenzahl & Tractinsky, 2006).

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However, empirical research addressing questions such as How to "measure" aesthetics?

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Whether aesthetics can be reliably differentiated from other aspects, such as usability? How

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important is beauty as a part of experience? What is the value, users attach to it? and What are

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"consequences" of beauty? is sparse and results are inconsistent.

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I believe that inconsistencies in findings can be at least partially resolved by

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distinguishing three different approaches to the study of beauty: a normative, an experiential,

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and a judgmental. The normative approach defines particular descriptive attributes of the

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interactive product as expressing more or less beauty (e.g., Ngo & Byrne, 2001). Such

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attributes can be, for example, symmetry or proportion. This approach further assumes

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symmetry to be more beautiful than asymmetry, particular proportions to be better than others,

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and so forth. Based on the objective configuration of attributes, it can then be decided whether

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the product is beautiful or ugly. The normative approach is primarily design-oriented. Thus, it

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starts from the materials (e.g., color, layout, form, movements) and attempts to provide a

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"recipe" of how to design something beautiful.

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The experiential approach focuses on all-embracing, holistic aesthetic experiences (e.g.,

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Frohlich, 2004; McCarthy & Wright, 2004) marked by an altered perception of one's

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surroundings or a scene – a heightened sense for objects, persons, the environment, which

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creates and attaches new, yet unthought meaning to things. The experiential approach is 2

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primarily concerned with preserving the complexity and richness of an aesthetic experience.

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Beauty is rather thought of as something rare, outstanding – a "design prize".

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Finally, the judgmental approach is concerned with what users judge to be beautiful or

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not (e.g., Tractinsky, Katz, & Ikar, 2000; Hassenzahl, 2004a). This approach is foremost

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interested in the consistency of beauty judgments among individuals and how fast and easy

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those judgments are (e.g., Lindgaard, Fernandez, Dudek, & Brown, 2006). In addition, it

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addresses the question of how beauty relates to other product attributes, such as novelty or

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usability.

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The present chapter focuses on the judgmental approach to the study of

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aesthetics/beauty. It starts with an attempt to define beauty in a way, which lends itself to its

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empirical/quantitative study in the context of HCI. This is followed by a review of research

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addressing correlates of beauty, primarily focusing on the relation between beauty and

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usability. After this, three consequences of beauty are considered in detail, namely beauty as

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added value, beauty as a way to accomplish self-referential goals and, finally, beauty as a way

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to work better. The chapter ends with a summary and conclusion.

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2 Beauty "defined"

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The appreciation and evaluation of a piece of art, such as Velázquez's "Las Meninas," is

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a complex process. Leder and colleagues (Leder, Belke, Oeberst, & Augustin, 2004) suggest

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the process to start with perception, followed by the implicit memory integration of the artwork

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with previous experience; the artwork's explicit classification in terms of style and content, its

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interpretation (cognitive mastering) and evaluation. The output of this process is an aesthetic

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judgment of the artwork. Clearly, such a judgment goes way beyond the mere appreciation of

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the artwork's visual quality. In other words, a piece of art can be good, without being

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necessarily visually pleasing (e.g., "DaDa"). Or it can be visually pleasing, without much

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quality (e.g., "kitsch"). In this sense, aesthetic judgment is very broad. It becomes aesthetic

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mainly because the judgmental object is a piece of art.

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In the context of HCI or interactive product design, such a broad definition of aesthetics

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can be problematic. Interactive products mostly serve purposes; they embody mundane action

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goals, such as "making a telephone call", "purchasing a flight ticket," or "ordering a book".

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This distinguishes them from pieces of art, which per definition do not serve personal goals

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other than enjoyment or creation of new insights. The appeal of an interactive product – its 3

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evaluation – can be the exclusive consequence of its functionality or usability. Being able to

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send email per Microsoft's Outlook is surely a useful and, thus, appealing possibility. If

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Outlook would be the only available tool to send mail, you surely would appreciate it, that is,

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you would appreciate the opportunity to send electronic mail. But would you consider Outlook

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as particularly beautiful, just because it enables you to send electronic mail?

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Some researchers, nevertheless, adopt a relatively broad definition of aesthetics in the

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context of interactive products, i.e., "non-aesthetic" objects (e.g., Lavie & Tractinsky, 2004;

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Park, Choi & Kim, 2004; De Angeli, Sutcliffe, & Hartmann, 2006). Park and colleagues (2004)

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explicitly state that aesthetic impressions can include qualities such as "adorable," "cool," or

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"strong," which are rather general evaluative terms. Unfortunately, this approach to beauty may

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lead to a substantial overlap with broader models of user perceived quality. Take Lavie and

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Tractinsky's (2004) two-component model of aesthetics as an example. They distinguish

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classical aesthetics (e.g., clear, symmetric, clean) and expressive aesthetics (e.g., creative,

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original, fascinating). The expressive aesthetics dimension, however, perfectly maps on the

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hedonic quality – stimulation dimension of my multi-component model of appealing products

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(e.g., Hassenzahl, 2003). Stimulation is the product's ability to satisfy human needs for novelty

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and curiosity. It is measured by attributes such as creative, original, innovative. It is impossible

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to decide, which of the two labels (expressive aesthetics vs. hedonic quality – stimulation)

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attached to the same underlying dimension (novelty, originality) is the more correct. The point

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is, however, that broad approaches to aesthetics may blur potential differences between general

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measures of appeal and aesthetics. By that, the concept of aesthetics loses some of its

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discriminant power. In addition, it must compete with existing multidimensional models of

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overall product appeal.

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A more concise definition of aesthetic judgment may stress the sensory – primarily

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visual – nature of input to judgment (e.g., Bloch, Brunel, & Arnold, 2003; Lindgaard &

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Whitfield, 2004; Hekkert, 2006). In other words, aesthetics may be narrowed down to the

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(mainly visually mediated) physical attractiveness of the product – its beauty. This has three

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advantages. First, the restriction of aesthetic judgment to judgments of beauty closely

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corresponds to laypersons understanding of aesthetics. A study of the associative words

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individuals generate for "aesthetics" (Jacobsen, Buchta, Köhler, & Schröger, 2004) showed

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"beautiful" and "ugly" to be the most prototypical for aesthetic judgment. Ninety-two percent

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of the 311 participants produced "beautiful," 42% "ugly" and 27% "pretty" as association to

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"aesthetics". This is in contrast to only 5%, who associated "aesthetics" with "attractive,"

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"enjoyable" or "cool".

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Second, beauty in this visual, physical sense can now differ from overall appeal. We

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may like products just because of their utility or usability, maybe even despite their obvious

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ugliness. Beauty discriminates. Hassenzahl (2004a), for example, studied judgments of

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goodness and beauty for mp3-player skins. Although both judgments were correlated (study 1:

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r=.54, study 2: r=.53 [pre-use], r=.39 [post-use]) – as would be expected for any evaluative

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construct – they also showed interesting differences. Goodness (as opposed to beauty) was

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related to usability (pragmatic quality), mental effort (induced by experience of usability

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problems), and was affected by experience. Note the reduction of the correlation between

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goodness and beauty after having used the products (from .53 to .39). Especially this

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dissociation, that is, the differential effect of product experience (as opposed to first

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impressions or in other words apparent versus experienced) on goodness and beauty

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judgments, justifies the more restricted definition. Just to give a further example, Mahlke

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(2002) found four independent aspects to contribute to the intention to use web sites. Among

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those, one was labeled "perceived visual attractiveness" (what I call beauty). Together with

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utility, usability and stimulation, it explained 72% of the total variance. Thus, beauty can be

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distinguished from other quality aspects and plays a significant role in the overall evaluation of

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the product.

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Third, only the restriction of aesthetic judgment to beauty makes it a truly neglected

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aspect in HCI. General user satisfaction (e.g., Lalomia & Sidowski, 1990) and technology

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acceptance (e.g., Davis, 1993) are well-researched topics. However, beauty in its narrow sense

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never played an explicit role in according models, not even in the presumably most

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comprehensive model of user acceptance, the unified model of user acceptance (UTAUT,

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Venkatesh, Morris, Davis, & Davis, 2003).

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Beauty judgments – in a narrow sense – are remarkably stable over time. Tractinsky and

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colleagues (Tractinsky, Cokhavi, & Kirschenbaum, 2004) as well as Lindgaard and colleagues

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(2006) consistently found a high retest-reliability for beauty judgments, even if the exposure

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time was as short as 50ms. This may be due to the fact that participants in both studies saw only

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images of products (websites) without having the possibility to interact with them, i.e., to

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experience them. However, Hassenzahl (2004a) showed a high retest-reliability (r=.87) of

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beauty judgments before and after having used a product, which was not mirrored by 5

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judgments of goodness (r=.46). The stability of beauty judgments, even in the face of actual

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product experience, supports the visual nature of beauty. Beauty – other than, for example,

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usability – can be more immediately assessed on the basis of the product's visual Gestalt.

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Moreover, key visual aspects are unlikely to change greatly over time. Both features make

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judgments of beauty fast and stable.

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Some authors do not explicitly distinguish between affect and beauty. Zhang and Li

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(2005), for example, subsume van der Heijden's (2003) "perceived visual attractiveness",

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Tractinsky et al.'s (2000) "perceived aesthetics" or Schenkman and Jönsson's (2000) "first

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impressions" as affective constructs. In this sense, beauty judgments become almost

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indistinguishable from perceptions of affective quality (Russell, 2003), i.e., an object's ability to

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impact a person's affective state. I wouldn't go this far. Surely, integral affective responses to

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objects, i.e., feelings either produced by the object's percept or its mental representation (Pham,

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Cohen, Pracejus, & Hughes, 2001), play an important role in any judgment. However,

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following an "affect-as-information" approach (e.g., Schwarz & Clore, 1983), those affective

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responses may rather serve as an input to the judgmental process than as the outcome. In this

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view, affective responses must, for example, be attributed to the visual Gestalt of the object and

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not to its content to be considered relevant for a beauty judgment. To give an example: a movie

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can feature a repelling story with beautiful images. Even if the initial affective response to the

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movie had been negative (triggered by the repelling story a friend told us about), this affective

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response is – if correctly attributed to the story – worthless for a judgment of beauty and its

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influence may be discounted or even corrected (e.g., Wegener & Petty, 1997). Nevertheless,

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although it may seem useful to separate affective responses from judgments of beauty, we may

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assume that beauty is more likely to be affect-driven than other more general, evaluative

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constructs. In other words, individuals may find it more adequate to allow for an affective basis

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of judgments of beauty compared to judgments of goodness.

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This has interesting implications. If we assume a simple two-stage judgmental process

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for product beauty, which uses immediate affective responses attributed to the percept of the

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product as an input, which then can – but must not necessarily – be further modified by

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previous experience, domain specific knowledge or personal tastes (see Leder et al., 2004),

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beauty judgments may show a higher interpersonal consistency than commonly expected. Pham

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and colleagues (2001) found individuals to agree more about their feelings toward targets

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(photographs, commercials) than about their overall evaluation. If, for example, beauty is more

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affect-driven than goodness, one should expect a higher interpersonal consistency for 6

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judgments of beauty. And indeed, in a meta-analysis of 102 studies (total number of

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participants = 15,681) of the ratings of human (facial) beauty, Langlois and colleagues (2000)

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report a surprisingly high interrater-agreement, within and across cultures. They came to the

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conclusion that the maxim "beauty is in the eye of the beholder" is a myth; people agree on the

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beauty (physical attractiveness) of other people. Whether the same holds for beauty of products

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has still to be demonstrated. In addition, the suggested two-stage model also implies that the

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consistency of beauty judgments maybe the higher, the less solid the judgmental basis. In other

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words, individuals confronted only with a 50ms exposure to a product's visual Gestalt may

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more heavily rely on their initial affective response, and thus, may be even more

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interpersonally consistent.

Let me summarize this section by a definition of beauty judgments, which I find appropriate as basis for further research in the context of HCI:

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A judgment of beauty is a predominantly affect-driven evaluative response to the visual

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Gestalt of an object. It takes the percept of the object and the integral (i.e., attributed) affective

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response as input. This input may be further modified by classification and comparison

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processes. Beauty's relative reliance on integral affect makes it faster and more consistent than

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complex judgments of goodness.

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In the following, I will first review literature on correlates of the beauty judgment.

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Based on this, three consequences of beauty are further discussed: beauty's value, beauty's self-

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referential nature, and the impact of beauty on task performance.

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3 Correlates of beauty

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3.1 What is beautiful is usable - Myth or Truth?

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Noam Tractinsky's (1997, Tractinsky et al., 2000; Lavie & Tractinsky, 2004) claim

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"What is beautiful is usable" received considerable attention in the HCI community. Norman

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(2004a), for example, took these findings to support his notion of "attractive things work

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better" (see section 4.3). Since then, Tractinsky's claim was repeatedly challenged. Hassenzahl

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(2004a), for example, found no correlation between usability (pragmatic quality) and beauty

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ratings for mp3-player with different skins (mean r=.07 [Study 1], mean r=.14 [Study 2, pre-

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use], mean r=.08 [Study 2, post-use]. In his own study of skins, Tractinsky and Zmiri (2006)

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obtained the same result (r=.03). Van der Heijden (2003) was able to separate visual 7

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attractiveness (beauty) from ease-of-use (usability) using principal components analysis with an

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orthogonal rotation, which implies independency of components (see also Mahlke, 2002).

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Lindgaard and colleagues (2006; see also Lindgaard & Dudek, 2002) studied the relation

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between beauty and ratings of other design characteristics. They found high correlations

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(smallest r=.93) with "interesting – boring", "good design – bad design", "good colour – bad

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colour", "good layout – bad layout", "imaginative – unimaginative", but not for "simple –

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complex" (r=.10) and lower for "clear – confusing" (r=.63). The latter are clearly usability-

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related attributes (Hassenzahl, Platz, Burmester, & Lehner, 2000; Hassenzahl, 2002). To

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conclude, whether what is beautiful is really usable remains inconclusive. Potential reasons for

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this lack of correspondence are manifold and may lie in differences of product genres

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(automated teller machines versus mp3-player skins or web sites) or differences in methods

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employed (see for an extensive debate Frohlich, 2004; Hassenzahl, 2004a; Monk, 2004;

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Norman, 2004b; Overbeeke & Wensveen, 2004; Tractinsky, 2004). Let me elaborate a bit

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further on two particular aspects that may influence the observed correlation between beauty

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and usability, namely the (1) type of correlation and (2) attribute overlap.

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3.1.1 Two ways to correlate

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In studies of beauty and usability two types of strategies can be distinguished (Monk,

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2004). The one aggregates (averages) ratings across individuals to derive a score on each

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attribute for each product and then correlates attribute scores (materials analysis, for an

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example see Tractinsky, 1997). The product serves as the focal point of analysis; variance

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introduced by individuals is discarded. A high correlation as result of this type of analysis

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indicates a sample of products that predominantly consists of high usability/high beauty and

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low usability/low beauty products. If stable, this may, for example, point at

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successful/unsuccessful underlying design practices, which contribute simultaneously to beauty

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and usability.

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The other type of strategy aggregates (averages) ratings across products to derive a

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score on each attribute for each individual and then correlates attribute scores (subjects

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analysis). The individual serves as the focal point of analysis; variance introduced by products

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is discarded. A high correlation in this type of analysis indicates that individuals, who find

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something usable may also find it more beautiful and vice versa. If stable, this may, for

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example, point at naïve theories of attribute covariation (akin to implicit personality theories,

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e.g., Schneider, 1973), which in turn serve as a basis for inference processes (e.g., Kardes,

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Posavac, & Cronley, 2004). To my mind, both strategies have their merits and should be 8

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addressed in future studies. Monk (2004), however, strongly argued for the materials strategies

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as the one better able to inform designers' work. Although I already took up this issue

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elsewhere (Hassenzahl, 2004b), let me devote some space to the question, why subjects

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analysis may be important, too.

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The goal of subjects analysis is to describe individual's naïve theories of attribute

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covariation. If beauty and usability correlate in a sample of individuals, that is, individuals who

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rated an object high on usability did the same for beauty and individuals who rated an object

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low on usability did the same for beauty, one may argue that both attributes belong together.

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People believe them to covary.

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Why is this important? As already pointed out, there is a striking difference between

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beauty and usability judgments. Because of its visual, affect-driven nature, beauty is much

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easier to assess than usability. Assessment of usability attributes, such as whether a product is

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"predictable" or "manageable" needs experience, i.e., usage of the product. Beauty does not.

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Thus, beauty – as based on immediately accessible information about the product (i.e., its

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visual Gestalt) – may be used to infer other, less immediately accessible qualities, such as

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usability or utility. In other words, individuals may infer unobservable attributes from beauty.

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Literature on consumer inference (see Kardes et al., 2004, for an overview) reports

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many types of inference strategies. Imagine being exposed to the – to you unknown –

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homepage of a new bank and someone asks you to judge its usability on a 0–100 scale, without

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being allowed to browse the page. One strategy is to estimate usability as discounted average

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on the basis of its known distributional properties (e.g., Johnson & Levin, 1985). In other

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words, you may know something about the distribution of usable banking websites (e.g., most

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of them are fairly usable) and, thus, infer that the website at hand might be similar (e.g., is

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fairly usable, too). You may further adjust this inference to the fact that you lack actual

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experience with the Website at hand. A second strategy is evaluative consistency (e.g., Lingle

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& Ostrom, 1979). Here an overall favorable impression derived from all observable attributes

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leads to a favorable impression on the unobservable attribute. If the banking website is

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beautiful, was recommended by a friend and the bank is well known, usability might be good,

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too. Note, that no direct causality is assumed, i.e., in the sense that beauty causes good

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usability. It is rather a "halo"-effect (Thorndike, 1920). The third strategy, however, implies

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causality. Probabilistic consistency inferences assume a causal link between an observable und

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the unobservable attribute (e.g., Ford & Smith, 1987). It would be given, if individuals assign a 9

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good usability to the website based on their assessment of beauty, because they believe beauty

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to cause good usability. A final possible strategy is compensatory inferences (Chernev &

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Carpenter, 2001). Individuals may believe that there ain't no such thing as a free lunch, and,

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thus, if a bank invested in its website's beauty other important attributes may not have received

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the same attention. In this case, beauty would lead to the inference of low usability.

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In a preliminary study of inference processes, I gave each of the 100 participants a list

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of 30 (hypothetical) mobile phones, each described on three attributes: price (range €40 to

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€400), functionality and beauty (both on a scale from 0 to 100, actual range 10 to 100). All

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three attributes were uncorrelated (no interattribute correlation larger than .08). The participants

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were asked to estimate each mobile phone's usability (0 to 100) on the basis of the available

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information. Correlations and regressions were calculated for each individual separately to get

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an idea of personal strategies. Interestingly, 53% of the participants showed a significant

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positive relation between beauty and their assessment of usability. Only three percent exhibited

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the inverse relationship of beauty and usability ("the dark side of beauty"), and the remaining

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44% failed to show any correlation. Thus, for slightly more than half of the participants beauty

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and usability was related. Of the 56 participants, who took beauty into account to predict

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usability, only two solely relied on beauty alone. The remaining relied on either two or three

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attributes. A stepwise group regression model showed functionality to be the best predictor of

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usability ratings (explained variance = 14%), followed by beauty (+3% explained variance).

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Price explained virtually no additional variance (+1% explained variance). All in all,

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individuals seemed to rely on an evaluative consistency strategy, where the quantity of an

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unknown attribute is inferred from the quantity of other attributes. Beauty played an – albeit

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compared to functionality minor – role in the inference of usability, which points at least to the

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possibility that beauty contributes to value and that from this value usability is inferred.

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To me, studies of inference processes involving usability and beauty seem a promising

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way to study the perceived relation between both constructs. Obviously, knowledge of these

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processes would not only be interesting, but also valuable to designers.

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3.1.2 Attribute overlap

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Another feature of usability and beauty, which may make correlation likely, is attribute

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overlap. Some attributes such as "clean layout" may contribute to both, beauty and usability.

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Indeed, I would attribute the observed high correlation between ratings of beauty and usability

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in, for example, Tractinsky's 1997 study (but only partially in Tractinsky et al., 2000) to this 10

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type of attribute overlap. In this study, 26 different layouts of automated teller machines (ATM,

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adapted from Kurosu & Kashimura, 1995) were used as products. Each layout consisted of the

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same basic elements (e.g., a number block, display). Variations in beauty were solely due to

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variations in the spatial layout. One-hundred and four participants rated each of the 26 layouts

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and ratings were averaged across participants (materials analysis). Beauty and usability was

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correlated. Without variation of other design dimensions, such as form, color, interactional

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style etc., the results can easily be interpreted as the consequence of a particular property of the

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spatial layout dimension varied, namely to impact both, beauty and usability. For example,

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Gestalt psychology's laws of organization (e.g., "proximity," see Goldstein, 1989, pp. 192) are

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regarded as both, a general theory of aesthetics and a central way to a "simple and natural

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dialog" with an interactive product (Nielsen, 1993, p. 118). In other words, correlation stems

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from the fact that distinct aspects, such as beauty and usability, partially rely on the same

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objective properties, such as layout.

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3.2 Other correlates

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In HCI, research on beauty and its correlates almost exclusively focused on beauty and

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usability (e.g., Tractinsky, Katz, & Ikar, 2000), with some notable exceptions. I (Hassenzahl,

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2004a) found a substantial relation between judgments of beauty and what I call hedonic

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product attributes in mp3-player skins, such as "inclusive," "presentable" or "brings me closer

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to people." This group of attributes was labeled identification. It captures the product's

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perceived ability to communicate a favorable Self to relevant others. This mirrors results by

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Tractinsky and Zmiri (2006), who found a high correlation (.72) between beauty and what they

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call "symbolism" (e.g., "positive message about user," "communicates desirable image").

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A more solid body of knowledge on beauty judgments resulted from the study of the

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physical attractiveness stereotype in social psychology. Starting with the seminal paper of

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Dion, Berscheid, and Walster (1972) entitled "what is beautiful is good," literally hundreds of

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studies explored further the basic finding that the physical attractiveness of a person (beauty)

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leads to more favorable evaluations on a variety of other, unobserved, yet relevant dimensions.

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Two meta-analyses concisely subsume the findings, one exclusively focusing on the attribution

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of unobservable, favorable traits to more or less beautiful strangers (Eagly, Ashmore,

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Makhijani, & Longo, 1991), the other (Langlois et al., 2000) extending findings by including

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actual behavioral consequences (i.e., number of sex partners, income) for beautiful and not so

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beautiful individuals, differences in treatment by others (i.e., giving recommendations for 11

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hiring, social attention), and self-perception (e.g., perceived happiness, perceived susceptibility

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to mental illness).

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Eagly and colleagues (1991) found a considerable effect of beauty on ratings of social

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competence (d=.68), but only a mid-size effect on intellectual competence (d=.46). General

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evaluations of persons were substantially affected by beauty (d=.57). First, these results may

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point at the primarily social nature of the beauty stereotype, because judgments of intellectual

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competence, i.e. the rational, pragmatic side of individuals, were less affected by beauty than

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judgments of social competence (but see Langlois et al., 2000, for less pronounced results in

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their review). Second, beauty substantially affected the general evaluation of a person (see also

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section 4.1), which in turn may lead to a more favorable judgment on any other attribute – at

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least if evaluative consistency is used as an inference strategy (see section 3.1.1).

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Although, it may seem questionable, whether results from the research on the beauty of

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persons generalize to the beauty of interactive products, the findings in HCI seem to mirror

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findings from social psychology where beauty is correlated with self-presentation (i.e.,

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identification, symbolism). As I put it elsewhere: "Beautiful people are assumed to better get

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along with others, to be more popular etc. Maybe people apply this general notion to objects as

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well, in the sense, that possessing beautiful things will help one to better get along with people

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and will make its owner more popular." (Hassenzahl, 2004b, p. 380).

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To summarize, research on correlates of beauty in HCI is sparse and inconsistent. This

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may be due to the different approaches taken. From the research so far, we may cautiously

22

conclude that beauty has self-presentational (i.e., social) implications. Its relationship to

23

usability is inconclusive. From a materials perspective (i.e., focus on products), it seems likely

24

that both attributes correlate mildly, because (1) they partially overlap and (2) good designers

25

may provide in general better quality than bad designers, that is, someone who cares about

26

beauty may also care about usability. From a subjects perspective, beauty and usability may

27

correlate as a consequence of an "halo"-effect. Specifically, people may infer a higher quality

28

of the product from its beauty (see section 4.1), which in turn implies a better usability. Note

29

that some may also hold a "what is beautiful is unusable"-stereotype based on the idea that

30

beauty is shallow and deliberately used to conceal deeper deficits (e.g., Russo & De Moraes,

31

2003). Literature on the physical attractiveness of people (Langlois et al., 2000), however, 12

1

failed to find strong evidence for such a "dark side" of beauty (e.g., the "dumb blonde"-

2

stereotype).

3

4 Consequences of beauty

4

4.1 Beauty as a source of value

5

Obviously, beauty is a source of value. In one study (Bloch et al., 2003, Study 7),

6

participants saw and rated pictures of two different toasters. While being equal in function, the

7

toasters differed in beauty. Among other things, participants were asked to state their

8

willingness to pay for both toasters. On average, participants were willing to spend $37.20 on

9

the beautiful toaster, but only $24.05 on the not so beautiful toaster. In other words, beauty was

10

worth $13.16, i.e. an increase of about 55%. In an unpublished study, I confronted participants

11

with the following hypothetical situation: Imagine, you have just bought a mobile phone for

12

€100.00. Immediately after the purchase, the dealer offers an alternative phone, which is –

13

everything else being equal – more beautiful. Participants were then asked to state the

14

maximum additional charge, they would accept for upgrading the phone. They were further

15

told that the dealer would either accept or reject the offer, depending on the amount offered,

16

and that no bargaining is possible. The average premium offered was €33.67 (95% c.i.: €24.99

17

– €42.34). Albeit slightly lower than in the toaster study, this is still a significant premium for

18

beauty.

19

Although the notion that beauty adds value seems intuitive, studies reveal a more

20

complex picture. Whether beauty adds value can depend on individual or situational aspects. In

21

the toaster study already mentioned above, Bloch and colleagues (2003) identified an

22

individual difference, the so-called centrality of visual product aesthetics (CVPA), as an

23

important moderator of beauty's value. CVPA subsumes three aspects: Value, acumen and

24

response. Individuals with a high CVPA attach personal value to beauty (e.g., "Beautiful

25

product designs make our world a better place to live"); they think of themselves as

26

connoisseurs, able to perceive the subtlest differences in beauty (e.g., "I see things in a

27

product's design that other people tend to pass over") and they strongly respond to beautiful

28

things (e.g., "If a product's design really 'speaks' to me, I feel that I must buy it"). High CVPA

29

individuals are more prone to use a visual style of processing, they more strongly desire to

30

acquire objects that only few others possess, and the acquisition of beautiful objects becomes a

31

central pursuit of their lives closely linked to happiness and success (Bloch et al., 2003, Study

32

4). In the toaster study, CVPA moderated the overall evaluation, purchase intention and the 13

1

willingness to pay for the two products (Bloch et al., 2003, Study 7). Whereas for low CVPA

2

individuals neither evaluation nor purchase intention varied significantly as a function of

3

beauty, it made a large difference for high CVPA individuals. The same pattern but not as

4

pronounced was also apparent for willingness to pay. On average, high CVPA individuals were

5

willing to pay $40.09 for the beautiful toaster; low CVPA individuals paid only $34.32.

6

This study demonstrated individual differences in the importance we attach to beauty

7

and consequently in the value beautiful objects have. Besides those individual differences,

8

situational aspects can determine whether beauty is valued or not. Ben-Bassat, Meyer, and

9

Tractinsky (2006), for example, attempted to measure the perceived value of beauty and

10

usability by the help of an auction mechanism. Participants first used and rated versions of a

11

software for text input, which differed in their usability and beauty. In the second part of the

12

study, participants were required to perform a task, i.e. to input items with the help of the

13

software. Task performance (number of items) was monetarily rewarded. Before the task,

14

participants were asked to place a bid on the version of the software, they would like to use for

15

the input task. Successful bidders were allowed to use the preferred version of the software for

16

the task. Bids had to be paid in real money. Interestingly, bids differed largely for the medium

17

and high usability version (NIS 6.54 [approx. â‚Ź1] and NIS 20.71 [approx. â‚Ź3.50], respectively),

18

but virtually no difference was found for the less and more beautiful versions. Participants even

19

seemed to pay slightly less for the beautiful, high usability version than for the less beautiful,

20

high usability version of the software. Thus, whether beauty has value depends on the context

21

the product is used in. In a highly efficiency-oriented context (as in Ben-Bassat's study),

22

individuals do not seem to place much value on beauty. In an unpublished study, Dieter Rhode

23

and I further explored the impact of situational cues on the centrality of beauty. We presented a

24

number of laptop desktops, which were meant to differ in beauty and usability. Each participant

25

rated the usability of each desktop (4 items, e.g., easy to use, concise), their beauty (4 items,

26

e.g. well-formed, beautiful look) and their overall adequacy (i.e. not adequate – adequate).

27

However, participants received different background stories for their rating task. One group

28

was told to imagine that they must later use the laptop for correcting a faulty and badly

29

designed PowerPoint presentation under time pressure. The second group was told to imagine

30

using the laptop for a series of important conference talks. The third group was told that the

31

desktop would be installed on their own personal laptop. As expected, in the first group

32

(revision of the presentation), the usability ratings were the single best predictor and explained

33

58% of the adequacy judgments' variance. The further inclusion of beauty into the regression 14

1

model explained only additional 9% of the variance (67% in total). Albeit significant, it seems

2

fair to conclude that beauty did not play much of a role for the adequacy judgments in this

3

group. This was different for the second group (conference talks). Usability remained the single

4

best predictor, but explained only 28% of the total variance. If beauty was added to the model,

5

explained variance was increased by 20% (48% in total). In the last group (own laptop), beauty

6

was the best predictor and explained 17% of the total variance. Usability added another 17%

7

(34% in total). Thus, for a highly task-related context (group 1, revision of the presentation)

8

beauty played only a minor role, which changed clearly given the context emphasizing self-

9

presentation (group 2, conference talks) or personal identity (group 3, own laptop). In these

10

cases, beauty mattered.

11

All in all, beauty can add value to a product. The magnitude of this effect is likely to be

12

moderated by personal as well as situational aspects. Some, more visually oriented individuals

13

may value beauty more than others. In addition, task- and efficiency-oriented contexts may call

14

for less importance of beauty than, for example, social contexts.

15

4.2 Beauty as appealing to self-referential goals

16

Typically, I distinguish between pragmatic and hedonic attributes of interactive

17

products (e.g., Hassenzahl, 2003), where – broadly speaking – pragmatic attributes relate to

18

action goals (either externally given or internally generated) and resulting tasks (e.g.,

19

"purchasing a flight ticket") and hedonic attributes relate to self-advancement and self-

20

presentation (are "self-referential"). Or as McGrath and Tschan (2004, p.49) put it, there are

21

goals, "which are clearly related to action content ('do goals', [go shopping])" and "more

22

general goals that are related the person's state or condition ('be goals', [be competent])". In

23

general 'be goals' are more abstract and more stable over time than 'do goals' (Carver &

24

Scheier, 1998).

25

As reported above, Hassenzahl (2004a) and Tractinsky and Zmiri (2006) found a

26

substantial relation between judgments of beauty and hedonic attributes, such as "inclusive",

27

"presentable," "brings me closer to people," "positive message about user," "communicates

28

desirable image" (see section 3.2). These attributes capture the products' perceived ability to

29

communicate a favorable Self to relevant others. Self-presentation is clearly a "be goal." Thus,

30

one may argue that beauty is related to, signals or is even a part of hedonic quality in products,

31

which in turn primarily appeals to self-referential goals, i.e., "be goals."

15

1

Importantly, people treat products differently depending on whether they are perceived

2

to be primarily hedonic or pragmatic (utilitarian, instrumental). Literature on consumer choice

3

(Dhar & Wertenbroch, 2000; Borcherding & Hassenzahl, 2004), for example, showed hedonic

4

aspects to be a moderator of the so-called endowment effect (e.g., Kahneman, Knetsch, &

5

Thaler, 1990). In short, individuals who own a particular object request more money to give it

6

up than others (or even the same individuals) are willing to pay for it. This gap between selling

7

and buying prices is a robust finding that is neither explained by strategic considerations (i.e.,

8

"buy low – sell high"), experimental artifacts nor inexperience with "market mechanisms." The

9

endowment effect may be interpreted as a form of "bonding" to the object. In other words,

10

higher selling prices result from a higher reluctance to part from the object. Indeed, Dhar and

11

Wertenbroch (2000) found a higher preference for primarily hedonic objects in a forfeiture

12

compared to an acquisition situation. In the acquisition situation, participants could either

13

choose between a $7 gift certificate for computer disks (primarily pragmatic) or a music CD

14

(primarily hedonic, Study 1). Fifty-four percent preferred the music certificate. In the forfeiture

15

situation, however, participants got both certificates first and were then informed that there had

16

been a procedural error and one of the certificates has to be given away. Interestingly, in this

17

situation 84% preferred the music certificate. In another study (Hassenzahl & Borcherding, in

18

preparation, Study 3), individuals were either asked to state their (hypothetical) maximum

19

buying or minimum selling price for a wristwatch in the range of €0 to €50. (In the selling

20

condition, individuals were asked to imagine they would own the watch.) For half of the

21

participants, the watch was described as primarily pragmatic (i.e., useful, effective, accurate,

22

reliable, robust); for the other half as primarily hedonic (i.e., exclusive, sporty, fashionable,

23

beautiful, valuable, dynamic). Note, that beauty was explicitly included in the hedonic

24

description. Participants, who found either watch relatively appealing, were willing to pay

25

about €30 for the primarily pragmatic watch, but only about €23 for the primarily hedonic

26

watch. This changed, however, for selling prices. Here, participants were willing to sell the

27

primarily pragmatic watch for about €29, but asked €32 for the primarily hedonic watch.

28

Consistent with Dhar and Wertenbroch's (2000) findings, the primarily hedonic object led to an

29

endowment effect (+€9) – an indicator for bonding – which was not apparent for the pragmatic

30

object. In other words, individuals may not be willing to pay much for beauty, but owning it,

31

they don't want to give it up either.

32 33

The observed reluctance to spend money on something primarily hedonic (lowest price in the watch-study) may also stem from difficulties of justifying the expenditure for hedonic 16

1

quality. In one study (Okada, 2005, Study 2) a certificate for a dinner in a restaurant (hedonic)

2

was rated as more attractive than a certificate for grocery (pragmatic), although both certificates

3

had the same nominal value of $50. In a combined choice situation, however, participants

4

preferred the pragmatic alternative. Okada (2005) argued this to be the consequence of a

5

justification process induced by the comparison of objects in the joint evaluation (choice)

6

situation. In such a situation, individuals construct reasons for justifying their choice. It may be

7

more difficult to envision reasons for primarily hedonic objects, because their benefits are often

8

rather difficult to state or even quantify. In addition, hedonic alternatives are often viewed as

9

wasteful and their acquisition or consumption is more likely to induce guilt (e.g., Prelec &

10

Loewenstein, 1998). These aspects all lead to the effect that the acquisition (buying) of a

11

hedonic object is harder to justify, and that it may not be chosen although it is more appealing

12

than an available alternative pragmatic object.

13

To summarize, I believe beauty to contribute to the hedonic quality of an object rather

14

than to its pragmatic quality. This self-referential, social nature of beauty has interesting

15

implications. On one hand, it may lead to a stronger bonding, as expressed by an endowment

16

effect. A primarily beautiful object is initially less valued compared to a more useful product;

17

however, if in one's possession the perceived value of beauty increases. On the other hand, the

18

acquisition of primarily beautiful objects may be harder to justify. Thus, although preferred,

19

people may not choose the beautiful product.

20

4.3 Beautiful products work better

21

In his recent book, Norman (2004a) made the claim that "attractive things work better"

22

(Chapter 1). He assumes the following mechanism for this somewhat surprising consequence of

23

beauty. Beauty leads to positive mood; positive mood facilitates creative thinking and problem

24

solving, which in turn improves task performance. No doubt, this claim is immediately

25

appealing to researchers in the field of beauty in HCI. Nevertheless, it calls for a careful and

26

critical examination of the underlying assumptions.

27

Starting from the beginning of the causal chain "beauty – positive affect – better task

28

performance," we may first ask whether a link between beauty and affect is likely. I assume

29

beauty and positive affect to be related (section 2). Specifically, a beautiful percept may elicit

30

an affective response, which is in turn – if attributed to the product (integral affect, e.g., Pham

31

et al., 2001) – used as an input to judgments of beauty and overall liking. Positive affect,

32

presumably caused by the percept of the object, but not attributed to the object (incidental 17

1

affect, e.g., Pham et al., 2001) will be experienced as mood (i.e., unattributed affect, Russell,

2

2003). Either way, beauty will have an impact on the initial affective state of the product's

3

users.

4

The link between positive affect and task performance is more questionable. In an

5

extensive meta-analysis of happiness and positive affect, Lyubomirsky, King, and Diener

6

(2005) reviewed a total of 92 studies, testing the effect of a mood induction procedure on

7

particular outcomes. The outcomes were further categorized into "positive perceptions of self

8

and others," "sociability," "negotiation," "prosocial behavior," "physical well-being," and

9

"creativity and problem-solving." The last category comes closest to task performance. In

10

general, the observed median effect size for this category was the smallest (median weighted

11

d=.25, largest was sociability, d=.56). In a more detailed account, Lyubomirsky and colleagues

12

(2005) came to the conclusion that induced positive affect no doubt fosters originality and

13

divergence in thinking. Concerning performance on complex mental tasks, however, results are

14

rather mixed: "it appears that sometimes the performance of people in positive moods is

15

superior, sometimes equal to, and at other times inferior to [...] those in a negative mood" (p.

16

839). The authors try to resolve these contradictions by referring to different underlying

17

processing styles triggered by the different affective states (see Schwarz, 2001). According to

18

this account, positive mood signals that everything goes well. Past successful strategies are

19

likely to work, which results in a stronger reliance on preexisting successful knowledge

20

structures. The processing becomes heuristic and holistic. In contrast, negative mood signals

21

problems, i.e., a failure of the actual strategy, which in turn leads to a more analytic and

22

detailed processing. Thus, depending on the properties of the task at hand, mood can result in

23

better performance (if the task calls for a holistic approach, such as finding a novel solution to a

24

problem) or worse performance (if the task calls for attention to details, such as solving

25

syllogisms). The authors conclude: "people experiencing happy moods have potential deficits

26

when it comes to problem solving, but they can overcome these deficits if they are motivated to

27

perform well at the task" (p. 840). Thus, the second part of Norman's claim may be viewed with

28

some reservation. First, it seems unclear, whether the handling of interruptions in goal-directed

29

behavior (i.e., overcoming a usability problem) calls for heuristic/holistic or analytical/detailed

30

thinking. Norman assumes the former because holistic thinking facilitates new, creative,

31

original solutions to problems (i.e., "seeing the forest for the trees"), however, reliance on

32

preexisting knowledge structures (Bless, Clore, Schwarz, Golisano, Rabe, & Wรถlk, 1996), one

33

of the consequences of heuristic thinking, may be rather detrimental for overcoming usability 18

1

problems. Second, effects reported in the literature are often obtained with the unobtrusive

2

induction of positive affect. This type of affect is called incidental affect. The type of affect

3

Norman assumes for his claim, however, is integral affect – a positive affective response to the

4

product at hand, i.e., affect attributed to the product. It seems plausible that positive integral

5

affect leads to a better evaluation of the product (as already argued for in section 2), and maybe

6

also that experienced affective reaction to the product colors mood. Nevertheless, this latter

7

step must be assumed, if Norman's assumed mechanism is to hold. Third, as already pointed

8

out by Schwarz (2001; see also Russell, 2003), affect's primary function is to signal an

9

individual's actual state. It is monitored constantly and changes over time. If, for example,

10

barriers to goal attainment arise, negative affective reactions are at the core to make the

11

individual aware of the problems. So, we may experience positive affect induced by beauty at

12

the beginning of the interaction, which in turn increases likelihood of exploration; however, the

13

moment the first severe problem arises, affect may change considerably to the negative.

14

Consequently, individuals engage in mood maintenance strategies. Handley and colleagues

15

(Handley, Lassiter, Nickell, & Herchenroeder, 2004), for example, set participants into either a

16

happy or neutral/sad mood. Participants were then asked to rank order eight different

17

hypothetical video films according to their liking. They were further told that their most

18

preferred film would be watched at the end of the experimental session. All film titles

19

contained only neutral words (e.g., "The walk from home"), however, some neutral words were

20

associated with positive words others with negative words in an according task before the mood

21

manipulation. Participants in a positive mood more strongly preferred films with a title, which

22

had been associated with positive words. Only 5% of the participants, however, reported mood

23

maintenance as a motive of their preference. In the same vein, individuals in a positive mood

24

bet less on a high-risk gamble (Isen & Patrick, 1983) and reveal a higher sensitivity to losses

25

(Isen, Ashby, & Nygren, 1988). Both were explained by the mood maintenance motive, which

26

increases the sensitivity to anything that is capable of disrupting the current positive mood.

27

Thus, to maintain our positive mood, we may rather stop interaction with a product that starts to

28

become troublesome than to be more willing to compensate problems as suggested by Norman.

29

To summarize, beauty will presumably has affective consequences. However, affect is

30

dynamic and subject to self-regulatory processes, which makes its impact on task performance

31

less straightforward. Moreover, an increase in divergent thinking and creative problem solving

32

may not be central to overcoming usability problems.

19

1 2

5 Summary and conclusion Beauty had been long neglected. The challenge for HCI is to integrate beauty (and other

3

hedonic aspects) into the field's research practices and practitioners' approaches to an

4

empirically driven user-centered design (i.e., processes, methods). The present chapter attempts

5

to facilitate this integration by defining the object of study, that is, beauty judgments, their

6

correlates and consequences.

7

First, it seems helpful to restrict beauty judgments to evaluations of a product's visual

8

Gestalt to avoid overlap with more general models of appealing products, user experience, user

9

satisfaction, or technology acceptance. Second, we may view beauty as primarily hedonic, i.e.,

10

more concerned with self-referential goals ("be") than action goals ("do"). Nevertheless, beauty

11

is often perceived first and relatively stable, which makes it an important starting point for

12

inference processes. Estimating hard to observe attributes (e.g., usability) from more readily

13

accessible attributes (e.g., beauty) is a complex process. However, as long as beauty contributes

14

to value and the overall liking of the product, this general "positivity" is likely to spill over to

15

other attributes, without a necessarily causal relation between attributes. Third, how much

16

beauty matters to each of us may depend on individual differences and situations. Social

17

context may call for beauty; strongly efficiency-related may not. Nevertheless, the link between

18

beauty and task performance is surely worth to be considered.

19

The study of beauty in HCI may be a big challenge; more importantly, I believe it to be

20

a big opportunity for the field. On the one hand, it opens up a wealth of interesting, stimulating,

21

exciting and thought-provoking research questions. On the other hand, a better understanding

22

of beauty is required to find suitable trade-offs between all the aspects making an interactive

23

product appealing. This may be the most important competence of future practitioners of HCI

24

(i.e., usability professional).

25

6 Acknowledgements

26

I'm very grateful to Paul Hekkert, Sascha Mahlke, Gitte Lindgaard and Noam

27

Tractinsky for their helpful and thought provoking comments on an earlier draft of the chapter.

28

(They may forgive my stubbornness concerning the one or other detail.)

20

1

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