INDIVIDUAL-DIFFERENCES IN THE PATTERN OF HABITUATION AT 5 AND 10 MONTHS OF AGE

Individual differences in pattern of habituation in fixation time and cardiac change to visual and auditory stimuli are described. Nearly half of the longitudinal sample at 5 months and almost 90% at 10 months did not display a monotonically decreasing habituation pattern over trials, a result that challenges the use of simple indices of response decline as measures of rate of information processing. A positive response to a novel stimulus at 5 and 10 months was observed only if an obvious peak response followed by a decline occurred during familiarization and (for 5-month-old subjects only) if the peak/decline occurred shortly before the introduction of the novel stimulus. Relative to 5 months, habituation patterns at 10 months were flatter and more irregular, and individual differences did not revolve around a few prototypical patterns. No evidence was observed for individual stability in type of habituation pattern across modality within an age or within modality across age, nor were there many correlates between pattern and demographic characteristics of the subjects. (PsycINFO Database Record (c) 2006 APA, all rights reserved).