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INDIVIDTJAL DIFFERENCES IN INFANT LOOKING: OLD QUESTIONS AND NEW DIRECTIONS

Janet E. Frick

Department of Psychology, University of Georgia, Athens, GA, 30602-30 13

Measures of visual fixation have long been used to study basic cognitive processes in nonverbal subjects, such as visual encoding, recognition memory, and attention. Interest in infant looking has further been fueled by the repeated observation that certain measures of infant looking are moderately correlated with cognitive performance in childhood and adolescence. New hypotheses about possible neural mechanisms underlying individual differences in measures of infant looking have been developed based on theoretical and methodological advances in cognitive neuroscience, which have identified specific brain systems controlling disengagement and movement of attention. Based on these findings, “marker tasks” have been developed to assess infant attention, and infant performance on these marker tasks can plausibly be linked to the developmental maturity of known neural attention systems.

One study conducted from this framework tested two hypotheses regarding individual and developmental differences in fixation duration, a measure of “infant looking” that has been shown to be related to later cognition. Infants may show long fixations to visual stimuli due to a general slowness in moving fixation through the visual field. Alternately, long fixations may be due to slowness in disengaging fixation from one stimulus, prior to moving to another stimulus. Three- and four-month-old infants were tested in a paradigm that measured their speed of shifting fixation to a peripheral stimulus under conditions in which a central fixation stimulus either did, or did not, remain illuminated (and thus, either did, or did not, “compete” for attention). Results indicated that infants were slower to shift fixation when the central stimulus competed for attention, and younger infants were especially slowed by this manipulation. Most interestingly, though, infants who showed longer fixations in a pretest were slower to shift fixation, but only in the competition condition.

These results are consistent with a model that attributes individual difference in fixation duration to neural fixation and/or attention systems that control disengagement processes. Thus, behavioral tests of infant looking can be used to bridge the gap between cognitive neuroscience and developmental psychology. Methodologies based on behaviors such as infant looking cannot, however, serve as a substitute for imaging-based assessment of brain function and activation, or for more direct measures of attention. It is important that care be taken not only to develop marker tasks that are consistent with the latest research, but to consider the potential importance of seemingly trivial methodological considerations, such as visual stimulus characteristics. Despite these caveats, behavioral tests of infant looking can complement knowledge gained in other fields and paradigms, and can serve to increase our understanding of the development of processes such as visual attention and memory that are important in both cognitive and social development. Work in this area will advance as multiple, converging measures are assessed simultaneously, such as studies incorporating both behavioral and physiological measures of attention, or studies incorporating both neural and behavioral measures of recognition memory.