Psychology: TestAS practice testlets

People must constantly make judgements under uncertainty, often quickly and with incomplete information. Instead of calculating probabilities, they use heuristics, mental shortcuts that usually work well enough but lead to systematic errors in certain situations. The psychologists Amos Tversky and Daniel Kahneman studied these heuristics from the 1970s onwards; Kahneman received the Nobel Prize in economics in 2002, partly for this work.

The availability heuristic judges the frequency or probability of an event by how easily examples come to mind. Events that are dramatic, recent or frequently reported in the media are recalled easily and therefore overestimated. After a plane crash is widely reported, many people overestimate the danger of flying, although driving the same distance is far more dangerous.

The representativeness heuristic judges the probability that something belongs to a category by how similar it is to a typical member of that category, while neglecting base rates, the overall frequency of the categories. Told that a quiet person likes order and detail, people tend to guess that he is a librarian rather than a salesman, even though there are many more salesmen than librarians.

Anchoring describes the tendency of an initial number, even an irrelevant one, to influence subsequent estimates. In a classic experiment, participants first spun a wheel of fortune that stopped at 10 or 65 and then estimated the percentage of African countries in the United Nations; those who had seen 65 gave much higher estimates. Anchoring affects price negotiations, where the first offer shapes the final agreement, and legal judgements.

Framing effects show that decisions depend on how options are described, even when the outcomes are identical. People prefer a treatment described as having a 90 percent survival rate to one described as having a 10 percent mortality rate. Related to framing is loss aversion: losses weigh roughly twice as heavily as gains of the same size, which explains why people often reject fair bets and hold on to losing investments.

Knowing about these biases does not make people immune to them, but structured procedures, such as considering base rates explicitly, seeking out disconfirming evidence and using checklists, can reduce their influence.

Learning is a relatively lasting change in behaviour or knowledge that results from experience. Behavioural psychology describes two basic forms of associative learning.

In classical conditioning, first studied systematically by Ivan Pavlov, an organism learns to associate two stimuli. Dogs salivate naturally when food is placed in their mouths: food is an unconditioned stimulus (US), and salivation is an unconditioned response (UR). If a neutral stimulus, such as a bell, is repeatedly presented just before the food, the dogs begin to salivate to the bell alone. The bell has become a conditioned stimulus (CS), and salivation to it is a conditioned response (CR). If the bell is then repeatedly presented without food, the conditioned response weakens and disappears, which is called extinction. Classical conditioning helps to explain fears and phobias, as well as taste aversions after food poisoning.

In operant conditioning, described by B. F. Skinner, behaviour changes because of its consequences. Reinforcement makes a behaviour more likely. Positive reinforcement adds something pleasant, such as praise or money; negative reinforcement removes something unpleasant, such as a headache that stops after taking a tablet. Punishment makes a behaviour less likely, either by adding something unpleasant or by removing something pleasant. Negative reinforcement is often confused with punishment, but it increases behaviour rather than decreasing it.

The timing of reinforcement matters. Continuous reinforcement, after every response, leads to fast learning but also to fast extinction when reinforcement stops. Intermittent reinforcement is slower to establish but more resistant to extinction. Reinforcement after an unpredictable number of responses, a variable ratio schedule, produces particularly persistent behaviour; slot machines use it.

Albert Bandura showed that people also learn by observing others, without being reinforced themselves. In his experiments, children who had watched an adult hit an inflatable doll later imitated this behaviour, especially if the adult had been rewarded for it. Observational learning explains how many skills and social behaviours are acquired.

Motivation influences whether learnt behaviour is shown. According to the Yerkes-Dodson law, performance rises with arousal up to an optimal level and falls when arousal becomes too high, and the optimal level is lower for difficult tasks than for easy ones.