Tom Minor Fiona Kyle Discuss the contribution of Gibson’s ‘ecological approach’ to perception to cognitive psychology. In terms of perception, cognitive psychology has offered a number of explanations: ‘Gestaltist’ views, ‘Constructivist’ understandings, and of course, the ‘Direct’ versus ‘Indirect’ argument; do we inferentially process the information we receive from our environment or is it purely ‘picked up’? This discussion will focus on a particularly influential theory of perception proposed by an American psychologist, James Jerome Gibson. His theory of direct perception has had a profound impact on cognitive psychology, going against all previous establishment theories and revolutionising the way in which perception is defined, indeed it implies a new theory of cognition in general. In psychology there is a distinction between sensation as the subjective experience or feeling that comes from excitation of the sensory receptors and perception as the sensory experience as interpreted from external stimuli, objects or events (Colman, 2001). A constructivist approach will be used to highlight some of Gibson’s achievements and theoretical flaws and a conclusion about the contribution Gibson has made to the study of perception within the cognitive field of psychology will feature at the close of this discussion. Perception is open to all sorts of biases and subjectivities and Gibson tried to account for these with his ecological approach, replacing the artificial way in which perception was tested in the static laboratory with real life test situations, hence the name: ‘Ecological Approach’. The real problem for Gibson was how one obtains constant perception in everyday life based on continually changing situations (Gross, 2001).
Gibson initially moved away from the traditional perception experiments with pictures, looking at what was seen with a single static eye, with a preference towards
experiments where the observer moved around freely, viewing many objects in natural conditions. Considering the way motion was perceived in ‘flow-lines’, and how target destination points provided height and speed estimations, Gibson, using Pilots as his participant group, analysed landing in fields and came up with his theory of ‘Ecological Optics’. This includes a description of optic flow and texture gradient whilst ignoring retinal images and active brain processes, in favour of regarding perception as ‘picking up’ information from the ambient light array (Gregory, 1998). The key assumptions of Gibson’s theory are that the optic array or pattern of light reaching the eye is structured and contains all the visual information from the environment. This array provides ‘invariant’ and ‘unambiguous’ information about the layout of objects in space through texture gradients, the optic flow and affordances. The final assumption is that perception involves picking up the information from the optic array directly via resonance and with little or no information processing (Eysenck, 2001). Optic flow patterns are characterised by the changes in the optic array as the perceiver moves around in their world (Gross, 2001). Affordances, according to Gibson, (1979) are the potential uses of objects that are directly perceivable; we learn which affordances satisfy certain goals and we also learn to attend to the appropriate aspects of the visual environment in order to pick up these affordances. Texture gradients are easily understood when one views a surface in perspective, elements that make up a textured surface appear closer together as the surface recedes. This gradient gives rise to a powerful impression of depth (Gibson, 1950; 1966; 1979). The final concept from this brief overview of Gibson’s main ecological theory is that of resonance. Resonance can be explained metaphorically as the nervous system working holistically for perception, like the circuitry of a radio for
listening to music. This deciphers how perceivers pick up information automatically if they are ‘tuned in’.
In support for Gibson’s theory it is correct that the environment provides much more information than was previously assumed (Eysenck, 2001). Gibson actually says that the environment seen at a particular moment doesn’t actually constitute the environment that is seen, implying that there is more to perceiving than just recognising what and where things are. This is an interesting parallel to Gibson’s argument that internal representations of an environment weren’t necessary, to which, Menzel, (1978) disregards with this study: Chimpanzees were carried around a forest whilst the carrier hid some logs of wood, when they were released the primates found the wood with no problem, even though the information for the light array wasn’t guiding them. This indicates the use of memorial representation and due to humans sharing so much brain anatomy with primates, it can be confidently inferred that humans are similar in this sense. Another supporting study for Gibson was conducted by Lee and Lishman, (1975), related to the belief in the importance of movement for perception. Noting how artificial the separating of sensory and motor aspects of behaviour was, Lee and Lishman created a ‘swaying room’ experiment causing the texture flow to change. The adults in the study unconsciously adjusted their footing so as to remain upright whilst the children tended to fall over! This raises the important issue of ‘time-to-contact’, one of the ideas that have come out of gibsonian theory. Time-to-contact basically refers to the mechanism used to avoid collision (and loss of balance) and grasp objects accurately, it reflects some very useful ecological information considering that we are in danger every day of colliding with something and we frequently need to grasp things in our every day life to survive.
Going back to Gibson’s rationale that affordances are merely picked up from a powerful visually guided context; the notion that information from the light is detected in order to organise activities and that a conceptual representation of the environment is redundant, Bruce and Green, (1990) disagreed. They asserted that it is inconceivable that we don’t need any knowledge about for instance, writing or the postal system in order to realise that a pen affords writing or a post box affords sending a letter, this information isn’t just directly perceived, it is inferred.
Constructivists use the retinal image as their starting point for perception (Gross, 2001), and one of the constructivist’s main proponents believes that meaningless sensory cues must be supplemented by memory, habit or experience in order to construct a meaningful environment (Gregory, 2001). Another constructivist, Marr, (1982) has criticised Gibson for underestimating the sheer difficulty of detection of things such as image surfaces, claiming it is an information-processing problem. He also states that Gibson’s approach applies much more to some aspects of perception than others. Generally, constructivists view perception as ‘for recognition’ but Gibson saw perception as something ‘for action’ (Eysenck, 2001). There may be different systems for both of these mechanisms. ‘Visual agnosia’ is when people have severe difficulties in object recognition whereas ‘optic ataxia’ is when someone has severe impairments in visually guided reaching; both these disorders stem from separate anatomical areas within the brain that are damaged and provide favour for the existence of a mutually exclusive theory of perception. On the basis that the constructivists use sub-optimal viewing conditions in their description of perception and Gibson reported only on optimal viewing conditions, it could be assumed that there is room for integration of the two theories. Goodale and Humphrey (1998)
believe that the constructivist and gibsonian approaches could be complementary rather than mutually exclusive because of the emphasis on different aspects of visual function. Something that has come out of this revelation is an, ‘analysis-by-synthesis model’ (Neiser, 1976), where the underlying theory is that perception is part of a cycle that involves schemata, perceptual exploration and environmental stimulus. The constructivists can account for visual illusions, which are heavily relied on in perception research to uncover the mechanisms that work in order to perceive. Unfortunately, Gibson cannot explain ‘mistaken perception’ and this is one of the theory’s greatest weaknesses. He argues that illusions occur in situations that are very different from those in the natural environment (Gross, 2001). It is well known, however, that illusions do occur in the natural or ‘ecological’ environment; the waterfall illusion is the most famous, so the ecological approach is in no way without flaw.
In many ways, Gibson’s radical way of dealing with some of the most complex issues in cognitive psychology have made strong cases for a need to reassess current methods of experimentation; his contribution to the aspect of movement. His outright denial of the more familiar ‘top-down’ views has certainly brought about a new awareness of the multiple levels involved in visual perception. He falls short, however, with definitional and semantic affairs (Fodor & Pylyshyn, 1981); what does ‘pick-up’ an ‘direct’ actually mean? If psychology is to fully appreciate the process of perception, clear constraints need to be put on these types of jargon. There is come contradictory as well as supporting evidence for Gibson’s work but as usual the negative press wins over and unless the need for mental representation and an explanation of visual illusions is put forward by the ecological approach, the
contribution of such an appeal is limited. Perhaps the best way forward is to recognise that there are gaps in Gibson’s theory and try and combine some of his best and provable ideas with the more traditional and consistent findings from the establishment theories to create an equally radical but reliable approach to perception.
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