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Chapter 1 Introduction to Personality Psychology 12

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FIGURE 1.1 A flyer advertising Francis Galton’s psychometric laboratory in London. Credit: K. Pearson, The Life, Letters and Labours . Wellcome Collection (CC BY 4.0). © Oxford University Press

stated in his famous paper, which was the output of his 1957 Presidential Address to the American Psychology Association (APA), in which he said: Psychology continues to this day to be limited by the dedication of its investigators to one or the other method of inquiry rather than to scientific psycholo gy as a whole. This is such an important distinction that it is well worth reading Cronbach’s paper (see ‘Guide to Further Reading’). Although Wundt was very well aware that significant individual differences existed in his

experimental measures, they were not his major re search focus. Now, the major problem with ignoring dif ferences between people is that often (indeed, typically) these differences account for much more variance than that which can be explained by experimentally manipu lated factors. If these differences reflect systematic vari ance and can be measured reliably, then it would seem sensible to consider it so to achieve the fullest possible account of the causes of behaviour. Namely, individual differences or the variance of the results indicating dif ferences between people are usually ignored in exper imental studies and treated as unsystematic factors or

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