Human Perception
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Choice of Action The output of decision making must be some action and the decision is based on the value of the action. A consumer’s decision can often be conceptualized as follow
Objects
Attributes
Importance
Price (1)
Warrantee (4) ………..
A
2
3
B
3
1
. . .
Object A: 2x1 + 3x4 = 14 Object B: 3x1 +1x4 =7
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Choice of Action •Rank order the importance (I) Attributes •Assign a value (V) to each attribute •For each product with highest sum.
This is referred to as compensatory decision making, since one small value can be compensated by another high value. The rule of Satisficing (Simon, 1955) is where people make a selection that is “good enough” – bypassing the results in the table. A more systematic heuristic that people sometimes apply is “Elimination by aspect” (Tversky, 1972). Here the most important attribute is first selected and products that are not in the top are eliminated.
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Choice under Uncertainty The expected value model Many decisions are made where we do not know what the outcome will be. This may be because we don’t understand the entire problem. A medical doctor may select a certain treatment, but he remains uncertain of the outcome.
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Prospect Theory Prospect theory is a behavioral economic theory that describes the way people choose between probabilistic alternatives that involve risk, where the probabilities of outcomes are known.
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Framing Effect The framing effect is an example of cognitive bias, in which people react to a particular choice in different ways depending on how it is presented; e.g. as a loss or as a gain. People tend to avoid risk when a positive frame is presented but seek risks when a negative frame is presented. The framing effect accounts for people’s when faced with a choice between a risk and a sure thing. Eg. The inconvenience cost of wearing safety glasses (which is known) outweighs the expected benefits of increased safety (unkown).
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Kahneman’s Gamble 1 Assume that you are given the choice of gambling (This time to win only) There are 2 options: A. You will obtain $10 with 100% certainty B. You will obtain $20 with 50% certainty and nothing with 50% certainty Would you choose A or B?
A – 75% B – 25%
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Kahneman’s Gamble 2 Assume that you are given the choice of gambling (This time loosing only) There are 2 options:
C. You will loose $10 with 100% certainty D. You will either loose $20 with 50% certainty or nothing with 50% certainty Would you choose C or D?
C – 75% D – 25%
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Pitfalls to accurate perception Attention and Cue Integration is a major challenge and there are 4 types of vulnerability •Information cue are missing •Cues are too numerous •Cues have different salience •Processed cues are not differently weighted
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4 types of vulnerability Information cue are missing E.g. A machine operator turns on a machine- but he did not know it was faulty. But a good operator may look for additional information and will often aware of what they do not know.
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4 types of vulnerability Cues are too numerous Limitations of human attention and working memory are great but people are not good at filtering relevant information. Following studies made supported the fact:
•Salience Bias: Paying most attention to salient information (Payne, 1980) •‘As if’ Heuristic: As if all information were equally valuable (Johnson, 1973). •Kanarick (1969) found that people prefer to buy unreliable, cheap information over accurate and expensive. •Rossi (1979) found that nurses count the numbers of symptoms- they were not influenced by the differences in diagnosticity.
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4 types of vulnerability Cues have different salience In practice operators have difficulties integrating and reasoning about more than 2 sources.
•Oskamp (1965) noted that when more information was provided to psychiatrists their confidence in diagnosis increased- but their accuracy decreased •Under time stress, decision making deteriorates when more information is provided (Wright 1974)
Nonetheless people have a tendency of seeking more information than they can absorb. –”all the facts on the table”! This is a dilemma in military command-control.
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4 types of vulnerability Processed cues are not differently weighted Sometimes information is distorted as it is passed from person to person- as it was the case of Vincennes. Some information is emphasized and some is forgotten. E.g. A poll of 10 persons is regarded as equally informative as a sample of 100 persons. The insensitivity to differences in validity and reliability of information makes people ill suited to make decisions based on many sources of information (Kahneman and Tversky, 1973) In these studies, subjects are given information about attributes that vary in weight, but people ignore arithmetic calculations (Rouse 1981). People should therefore only identify what criteria are important, and leave the calculations to a machine.
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Expertise and Cue Correlation We identified 2 important biases In decision making: •Saliance Bias: Paying most attention to salient information (Payne, 1980) •As if Heuristics: As if all information were equally valuable (Johnson, 1973). But there are many situations where these issues are unimportant. For example , there may be scenarios where several cues are correlated and equally weighted. If so, there can be an intuitive information integration. (Hammoned 1987) It would of course take some time to learn the correlation patterns-as with other task.
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Some decision are formed over time: But can they survive the biases from Anchoring, Overconfidence and Confirmation.
Many diagnose are not quick, ‘one shot’ pattern classifications, such as in RPD. But decisions are formed over time: Jurors in a trial, trouble shooting, etc. There are 3 characterastics which work against a good decision: •Over confidence Bias •Anchoring Heuristics •Confirmation Bias
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Overconfidence Bias People are often over-confident in their beliefs. The average driver thinks he/she is among top 25% of drivers, accidents happen to others. Fischhoff (1982) asked people to predict the outcome of sports events. Then they asked them to rate their confidence in the prediction. Comparing to the accuracy to the confidence they found that confidence exceeded accuracy by 20%-30%. The same applies to general knowledge and eyewitness reports. People will prematurely stop to look for more evidence.
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Anchoring Heuristic Not all hypothesis given the same fair chance to “win�. That is a mental anchor. Weather forecasters will ignore information that disconfirms their first hypothesis (Einhorn, 1982)
A study by Tolcott et al (1989) showed that army intelligence officer's give more weight to initiate information than following contrary information. Although primacy may bias a decision, there is also evidence that recency may bias. The lawyer that goes second can bias a jury in making their judgment, particularly if the information is complex. Complex information
Influence
Simple
Compare to Primacy in Memory
time Serial Positioning Effect MA4847 Human Factor Engineering
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The confirmation bias Cues that confirm a bias will be counted, but disconfirming cues will not. We have already made up our mind and we will not look for negative informationjust positive.) Neutral information will sometimes be counted as confirming information. This produces “Cognitive tunnel vision”
On the USS Vincennes radar operators hypothesized early on that the approaching aircraft was hostile. They did not interpret contradictory information as – contradictory. At the Three mile Island operators focused on a display that indicate that a relief valve had closed (this was wrong). They searched for confirming evidence that the water level was too high- it was actually too low.
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The confirmation bias There are three reasons for this bias 1. people have cognitive difficulties in dealing with Nick at the evidence. 2. To change a hypotheses requires much effort. 3. Self-fulfilling prophecy. A child who is diagnosed as “gifted” will get extra attention. Confirmation bias is not necessarily bad. It may be better to maintain a workable framework, rather than “blindly searching” for hypotheses. The problem is to make decision makers consider disconfirming evidence.
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Implication of Biases and Heuristics in Diagnoses Nonetheless we need to go beyond the view that human are just a “bundle of biases� Many of the heuristics are highly adaptable for a decision maker who must work quickly. In fact people use heuristics because most of the time they work well. As noted a fire captain must depend on RPD- a delay could cause loss of lives. Understanding the types of biases can also suggest areas for training.
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Estimating Cues: Perception Many of the cues for a decision problem are probabilistic in nature. Human do a good job at estimating an average value of a set of observations (Sniezek, 1980). Humans can also estimate proportions- as long as they are between 0.05 and 0.95. However the estimate of more extreme proportions tends to be conservative. Never say never (0), never say always (1.0)
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Assume you have 2 different populations with the same variance but different means. People tend to estimate the variance of the greater mean as smaller.
A (length). Variance in length is estimated greater to the left than to right
B (position). Variance in position is estimated greater to the right
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Conservatism in extrapolation Humans are not good at extrapolating trends. On the other hand, most exponential curves to correct themselves to slower growth- eventually.
Quantity
Continued exponential growth
People’s extrapolation
Present MA4847 Human Factor Engineering
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People are good at estimating means but bad at estimating variances, probabilities and trends. Whenever possible the system should display parameters such as variance and probability and trends, rather than letting people estimate them.
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Human Information Processing
Adapted from Wickens, C.D., Engineering Psychology and Human Performance, Harper Collins, New York, 1992. MA4847 Human Factor Engineering
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Population Stereotype What is population stereotype? -Not an intrinsic property of human cognitive system -A product of collective experience for specific group or population although some beliefs are becoming generic -Can change with time and experience -Can differ across countries and cultures Example: Showing teeth=aggression or accepted greeting? Design of light switches, traffic lanes.
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Perception Human perceive something with senses. Perception is the process by which sensations are organized and interpreted to form an inner representation of the world. Perception refers to the interpretation of what we take in through our senses.
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Sensitivity of Senses
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Human Vision: Physiology of the Eye
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Human Vision: Physiology of the Eye
Eyeball rotation: orbital muscle MA4847 Human Factor Engineering
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Human Vision: Physiology of the Eye
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Human Vision: Physiology of the Eye
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Human Vision: Physiology of the Eye
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Human Vision: Physiology of the Eye
Fovea: ability to resolve fine details (almost all cones only). Peripheral Vision: High density of rods. Sensitive to motion but supports only 15-50% of the fovea.
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Eye Test
https://www.youtube.com/watch?v=YaBKXVGe2Z8 MA4847 Human Factor Engineering
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The Mystery of the Red Cards
https://www.youtube.com/watch?v=QpvEmNKyg9A MA4847 Human Factor Engineering
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End
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