Causes of intraindividual variability in reaction times: a neurophysiologically oriented review and a new suggestion

Journal/Book: Pers Indiv Differ. 1998; 25: The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, England. Pergamon-Elsevier Science Ltd. 991-998.

Abstract: Inter-individual variation in reaction times, and its negative correlation with intelligence, has long been established. Marked intra-individual variability in reaction times, within a given RT paradigm, has also been known for decades but, in contrast, is still unexplained and is usually ignored. Jensen [Jensen, A. R. (1980) Bias in mental testing. New York: Free Press; Jensen, A. R. (1982) Reaction time and psychometric g. In H. J. Eysenck (Ed.), A model for intelligence. Berlin: Springer; Jensen, A. R. (1992) The importance of intraindividual variation in reaction time, Personality and Individual Differences, 13, 869-881.] has proposed an ''oscillation model'' in which a reaction stimulus-induced evoked potential interacts with ''brain waves'' (EEG) to make RTs vary from trial to trial within one test session. Anderson [Anderson, B. (1994) Speed of neuron conduction is not the basis of the IQ-RT correlation: Results from a simple neural model, Intelligence, 19, 317-324.] and Anderson and Donaldson [Anderson, B., & Donaldson, S. (1995) The backpropagation algorithm: Implications for the biological bases of individual differences in intelligence, Intelligence, 21, 327-345.] have used simple computer models of connected neurons and neural nets, respectively, varying the values of certain parameters such as synaptic failure rates, to explain RT variability. I discuss these models and argue that they do not explain the observed variability. A new possible explanation is proposed here: intraindividual RT variability follows from variable (within a S, between individual RT trials) cortical pathway length (CPL), where CPL is the total length of the neural pathways in the cerebral cortex which an RT-induced evoked potential must follow in executing a correct RT response. This is an extension of the inter-individual CPL variability proposed by Reed and Jensen [Reed, T. E., & Jensen, A. R. (1993) Choice reaction time and visual pathway nerve conduction velocity both correlate with intelligence but appear not to correlate with each other: Implications for information processing, Intelligence, 17, 191-203.]

Note: Article Reed TE, Univ Toronto, Dept Zool, Toronto, ON M5S 3G5, CANADA

Keyword(s): reaction time; Intra-individual variability; EEG; brain nerve conduction velocity; INDIVIDUAL-DIFFERENCES; CONDUCTION-VELOCITY; INTELLIGENCE; PATHWAY

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