Rate of habituation and the response to novelty and discrepancy in four-month-old infants
Ritz, Elsbeth G.
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Previous investigators of infant visual attention have employed the habituation procedure to study the growing memory processes of the infant. Typically, researchers have manipulated the type of visual stimulus used to habituate the infant and have found that different types of visual stimuli elicit unique distributions of infant attention (fixation). Investigators have also explored the role that rate of habituation plays in infant visual attention. Results have been equivocal as to whether differences exist between fast and slow habituators in their magnitude of recovery to a stimulus. The present study was designed to determine if this discrepancy in results between studies was due to the type of stimulus variable manipulated (i.e., discrepancy or novelty). Thus, it was hypothesized that if the dishabituation and habituation stimuli distinctly differed in a large degree of discrepancy, then slow habituators would exhibit a greater magnitude of recovery of fixation time than fast habituators. In addition, the present study was designed to determine if there was a difference between fast and slow habituators in the magnitude of response recovery when the dishabituation stimulus differed from that used during habituation along the novelty dimension. Finally, since few studies have attempted to determine if rate of habituation is a stable measure of an infant's visual attention, subjects participated in two habituation sessions which took place exactly one week apart. Forty-eight four-month-old infants, 24 males and 24 females, were presented with either a novel or a discrepant visual rehabituation stimulus following habituation to a standard stimulus. On Day 1, as hypothesized, slow habituators exhibited a greater amount of recovery of fixation time than fast habituators when the habituation and dis- habituation stimuli differed to a large degree along the discrepancy dimension. In addition, on Day 1, it was found that slow habituators exhibited a greater amount of recovery of fixation time than fast habituators when the habituation and dishabituation stimuli differed along the novelty dimension. These findings were interpreted as indicating that two different cognitive processes were involved when an infant was presented with a discrepant versus a novel stimulus. The Day 8 data, however, did not support Day 1 findings. That is, no significant differences between fast and slow habituators were found in their amount of recovery to either a discrepant or a novel stimulus. In fact, a general lack of stability in infants' rate of habituation to a visual stimulus was found over the one-week interval. While rate of habituation has been considered by many to be an important determinant of cognitive level in infants, the data of the present study support the notion that rate of habituation is simply a temporary characteristic of an infant's attention. Thus, it was suggested that rate of habituation should not be used as an index of the global level of cognitive development in infants.