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Thomas Baker, Scott Adler; Saccadic reaction times and speed of information processing development. Journal of Vision 2008;8(6):916. doi: 10.1167/8.6.916.
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Infants speed of information processing (SIP) has typically been assessed by habituation and preferential looking paradigms (see Bornstein, 1998; Orlain & Rose, 1997). These kinds of tasks, however, are incongruent with how SIP is assessed with adult populations and differ from adult theories of SIP (Jensen, 2005; Smith, 1968). With adults, the manual reaction time (RT) to press a button (among several choice buttons) is usually taken as an index of SIP (Hick, 1952; Jensen, 1987). Consistently it has been found that manual RTs increase with the log2 of the number of choices, or bits of information, (Jensen, 1987) which has become known as Hick's law (Hick, 1952). Although infants cannot perform manual button responses, they can provide us with saccadic RTs. In the present study we measured 5- and 9-month-old infants' saccadic RTs to increasing bits of information in a visual choice RT task. Five-month-old infants' saccadic RTs increased with more bits of information in accordance with Hick's law. Nine-month-old infants' saccadic eye RTs did increase with more bits but not to the extent as the younger infants. Adults showed no increase in saccadic RTs with increased bits of information, which is consistent with past studies (e.g. Kverega, Boucher, & Hughes; Saslow, 1967). These data indicate that as infants age, and presumably as their SIP becomes faster, they are able to process more information per unit of time. Thus, there appears to be a developmental trend that occurs with measuring SIP through saccadic eye movements. By using this method of measuring SIP in infancy we are better able to make direct comparisons to the adult literature.
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