With his 1954 book The Nature of Prejudice, American psychologist Gordon Allport displays the crucial skill of reasoning, producing and organizing an argument that was persuasive enough to have a major impact not only in universities, but also on government policy. The question that Allport tackled was an old one: why are people so disposed to prejudice against those from other groups? Earlier psychologists had suggested a number of reasons, especially in the case of racial prejudice. Some had suggested that racism was a learned behaviour, conditioned by negative experiences of other races; others that there was an objective rationale to negative racial stereotypes. Allport, however, reasoned that prejudice is essentially a by-product of the necessary mental shortcuts the human brain uses to process the vast amount of information it takes in. Because our brains want to use as little effort as possible, they regularly fall back on simple stereotypes – which easily generate prejudice. Gathering strong evidence for this hypothesis, he reasoned, clearly and persuasively, that our natural cognitive approach is the most significant factor in accounting for prejudice. Going further still, Allport also reasoned that, once this was better understood, social scientists would be able to influence policy-makers to curb discrimination by law.

The work of memory researchers Alan Baddeley and Graham Hitch is a prime example of the ways in which good critical thinkers approach questions and the problems they raise. In the 1960s, researchers into human memory began to understand memory as comprising not one, but two systems. The first was a short-term system handling information for mere seconds. The second was a long-term system capable of managing information indefinitely. They also discovered, however, that short-term memory was not simply a ‘filing cabinet,’ as many had thought, but was actively working on cognitive – or mental – tasks. This is how the phrase “working memory” developed. The hypothesis remained unproven, however, presenting Baddeley and Hitch with the problem of working out how to produce definitive evidence that short term memory was a working system that actively manipulated and processed information. They responded by designing a series of ten experiments aimed at showing just this – presenting the results in their 1974 article, ‘Working memory.’ The research was a masterpiece of problem-solving that proved revelatory. The authors not only generated new solutions and made sound decisions between alternative possibilities – they also showed that short-term memory is indeed an active system responsible for information processing and managing, while also influencing attention, reasoning, reading comprehension and learning. While their work has since been refined by others, Baddeley and Hitch’s problem-solving approach helped to create the dominant understanding of working memory that underpins psychological research throughout the world today.