Individual Differences

Introduction to Individual Differences

Last updated:
31 Mar 2007

Individual differences is a cornerstone subject area in modern psychology.  In many ways, it is the "classic" psychology that the general public refers to - it refers the psychology of the person - the psychological differences between people and their similarities.

Plato stated more than 2000 years ago:

“No two persons are born exactly alike; but each differs from the other in natural endowments, one being suited for one occupation and the other for another.”

Individual difference psychology examines how people are similar and how they differ in their thinking, feeling and behaviour.  No two people are alike, yet no two people are unlike.  So, in the study of individual differences we strive to understand ways in which people are psychologically similar and particularly what psychological characteristics vary between people.

In the Western psychology approach to individual differences, it is generally assumed  that:

  • People vary on a range of psychological attributes
  • It is possible to measure and study these individual differences
  • individual differences are useful for explaining and predicting behaviour and performance

We can classify people psychologically, according to their intelligence and personality characteristics, for example, with moderate success, however people are complex and much is still left unexplained.  There are multiple and often conflicting theories and evidence about individual difference psychology.

Human beings have been aware of individual differences throughout history, e.g.

  • Gender differences -hunters=men, gatherers=women
  • Intelligence differences - caste, class, education, etc.
  • Personality differences - job specialisations

Early study of individual differences

We have come a long way since Franz Gall invented phrenology in the early 1800s. Phrenology is the study of an individual's bumps on the skull, which supposedly reveal character traits and mental abilities.

Phrenology had such vogue that by 1832 there were 29 phrenological societies in Britain and many journals in both the UK and US devoted to the study of phrenology. It was seriously proposed to select Members of Parliament from their "bumps". Some phrenologists even moulded children's heads to accentuate good qualities and minimise bad ones!

Despite the theory being incorrect one of its assumptions holds true: the idea that various brain regions have particular functions.

Darwin suggested that nature selects successful traits through the “survival of the fittest”. His cousin, Sir Francis Galton (1822-1911) concluded that he could apply the principle scientifically. Why not measure human traits and then selectively breed superior people? He assumed human traits, everything from height and beauty to intelligence and ability, to personality traits such as even-temperedness, were inherited.

Modern psychology has formalised the study of individual differences over the last 100 years.  Individual differences psychology is still a young science and a relatively recent development in modern psychology.  There are still many debates and issues. Current knowledge will change and evolve.  So, have an open-minded, but critical perspective as we go along!

Since there are multiple and controversial viewpoints, it is necessary to move beyond reliance on personally preferred viewpoints to also embrace alternative perspectives, particularly those which are utilized in psychological practice and which have solid research support.


Wikipedia (2007). Individual differences psychology.