“Individual differences” (also known as “differential psychology”) is the area of psychology concerned with the scientific understanding of how, why, and to what degree people differ. Its two major objects of study are personality and intelligence, though emotion, motivation, vocational interests, and creativity also represent important, and increasingly researched, topics. Thus, individual difference factors attempt to describe and explain the nature, causes, and consequences of any psychological differences between individuals. Typically, such differences are quantified and measured or assessed via psychometric tests (Chamorro-Premuzic & Furnham 2005).
“Information processing” is a paradigm that originated within the cognitive psychology movement of the 1940s to explain human thinking via a series of mainly computational or cybernetic metaphors (e.g., human brain acting as hardware vs human mind acting as software). More generically, information processing refers to the psychological mechanisms by which humans perceive, encode, decode, acquire, retain, and retrieve information; in simple terms, how we make sense of the perceptual and symbolic world around us.
While the core aspects of information processing are, by definition, ubiquitous in the human species (this is largely the premise of cognitive and experimental psychologists), individuals do differ in their processing of information. In fact, differential psychologists have attempted to link specific patterns of behavior, thought, and emotionality to different aspects, and modalities, of information processing. Thus, individual differences in information processing explain and highlight variability, rather than similarities, between people, or the psychological causes that make information processing different in different individuals.
Affect – whether its ephemeral and object-based version of emotion, or its longer lasting, object-free version of mood – and cognition are known to be influenced by individual differences. For instance, information processing is very different under positive and negative affects.
Crucially, people differ in their likelihood and predisposition to experience both positive and negative affect (Watson & Tellegen 1985). Some individuals are more likely to be happy or cheerful, while others seem sad and pessimistic most of the time and quite irrespective of the situation. These two, opposite, types of individuals will also differ in their characteristic patterns of information processing: one may interpret a situation as positive, while the other interprets the same situation as negative.
Individual differences in stable personality traits influence people’s patterns of behavior, thought, and emotionality. In particular, neuroticism seems to exert a strong influence on individuals’ tendency to experience negative affect, whereas extraversion predisposes people to experience positive affect (Costa & McCrae 1992).
The interaction between individual differences and information processing is often complex. Appraisal theory, one of the dominant psychological approaches to the study of stress, postulates that emotions are largely a function of an individual’s interpretation of (1) the event (in the case of stress, the level of threat posed by it), as well as (2) their capacity to handle that event (e.g., cope with the threat). As such, stress is more influenced by individuals’ subjective evaluations (appraisals) of an event than the event itself. This explains why certain individuals may experience high levels of stress in situations that are experienced as pleasant by others (see Lazarus 1999).
Traits, such as neuroticism and extraversion, “distort” (bias) individuals’ interpretations of events and, in turn, lead to individual differences in vulnerability to experiencing stress. While the experience of stress itself produces similar information processing patterns in all individuals, the vulnerability to experiencing stress is a function of individual difference factors (Matthews et al. 2003).
Another example of the interplay between individual differences and information processing is reflected in so-called “cold” tasks (e.g., math problems, IQ test performance, and target detection). When individuals complete such tasks, their performance is affected by a variety of cognitive and affective states. Many of these states are “task-irrelevant” in that they do not advance or help, but actually hinder, task execution, diverting attention away from the target stimuli and taxing working memory (see Szalma & Hancock 2005 for a recent review).
Cognitive approaches to individual differences in information processing tend to investigate intellectual abilities, particularly the biological or “fluid” aspects of intelligence. This line of research dates back to the very beginnings of ability testing, notably to J. M. Cattell’s (1890) attempts to quantify individual differences in tactile, weight, and hearing discrimination. More than a century later, there is wide consensus among mainstream IQ researchers that these aspects of information processing represent the very essence of individual differences in intelligence, serving as “raw” and universal measures of brain efficiency.
Indeed, intelligence researchers have long speculated on the possibility of IQ being ultimately a measure of neural efficiency or neural speed (Jensen 1998). The idea underlying this approach is that more efficient brains should be capable of faster and more accurate processing, which, in turn, is advantageous for information acquisition. However, measures of reaction time, information processing, perceptual speed, or inspection time, as measures of neurophysiological activity, are poorer predictors of learning ability and educational/occupational outcomes than are broader intelligence tests, such as those including verbal, mathematical, and logical problems.
- Cattell, J. M. (1890). Mental tests and measurements. Mind, 15, 373 –381.
- Chamorro-Premuzic, T., & Furnham, A. (2005). Personality and intellectual competence. Mahwah, NJ: Lawrence Erlbaum.
- Costa, P. T., Jr., & McCrae, R. R. (1992). Revised NEO Personality Inventory (NEO-PI-R) and NEO Five-Factor Inventory (NEO-FFI) professional manual. Odessa, FL: Psychological Assessment Resources.
- Jensen, A. R. (1998). The g factor. Westport, CT: Praeger.
- Lazarus, R. S. (1999). Stress and emotion: A new synthesis. London: Free Association Books.
- Matthews, G., Deary, I., & Whiteman, M. (2003). Personality traits, 2nd edn. Cambridge: Cambridge University Press.
- Szalma, J. L., & Hancock, P. A. (2005). Individual differences in information processing. In D. K. McBride & D. Schmorrow (eds.), Quantifying human information processing. Lanham, MD: Lexington Books, pp. 177–193.
- Watson, D., & Tellegen, A. (1985). Consensual structure of mood. Psychological Bulletin, 98, 219 –