Human decision making

Our daily lives are filled with decisions, big and small. Should I have coffee in the morning? Should I take the bus or a cab? Should I wear the blue shirt or the white one? Many of these decisions are made so rapidly that often we don’t spare them a single thought.

But cognitive psychologists are slightly different. They have spent years wondering about the decision making process of humans. Kahneman and Tversky have outlined 3 heuristics that humans regularly use – the availability heuristic, the representativeness heuristic and the anchoring and adjustment heuristic.

The availability heuristic involves making judgements about the probability of an event by assessing the ease with which the relevant mental operation of retrieval, construction or association can be carried out, i.e. we are more likely to judge a stimulus as more probable if we can readily bring to mind specific instances of that event. However, the ease with which a stimulus can be brought to mind does not simply depend on how probable it is, but also with factors like how recently we were exposed to the stimulus and how familiar we are with the stimulus. Thus this reasoning can lead to faulty decision making. For example, Kozielecki et al found that people who are more familiar with instances of divorce within their family tend to judge the probability of divorce as much higher than those who are less familiar with divorce amongst their family.

The representativeness heuristic involves judging a sample to be more likely to occur or being more probable if it is similar in important aspects to the population to which it belongs and if it looks random, given the fact that it is known to be selected by a random process. Thus if a coin is flipped 6 times and one is provided 3 alternatives about the sequence of the outcomes as 1) HHHHHH, 2)HHHTTT and 3) THHTHT, the third outcome is judged as more likely to occur, even though the true probabilities of all three alternatives are the same. When using the representativeness heuristic, individuals do not take into account information about the sample size and base rate.

According to the anchoring and adjustment heuristic humans first make an approximate, intuitive guess about the correct decision in a situation. This initial guess acts like an anchor in that, it ties us down and has an undue influence on the final solution. Thus, minor and trivial adjustments are made to the initial guess based on additional information that the individual gets and the final decision is made.

Even though Kahneman and Tversky focus on cognitive biases due to the use of heuristics, there is another approach to the study of the same. Gigerenzer uses the adaptive thinking approach. He proposes that humans use heuristics because they do in fact work most of the time, i.e. they have an adaptive value in the sense of ensuring a successful or satisfactory decision.

Pritha Sengupta

Pritha Sengupta


IRIANS- The Neuroscience Institute


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