Examining a Common Method of Measuring Infant Fear: Considering Temperament, Neurophysiology, Age, and Sex Differences.

The pre-locomotor version of the Laboratory Temperament Assessment Battery (Lab-TAB) provides one of the most widely used observational measures of fear based on the infant's reactivity to a series of four novel masks. Resulting indicators of facial and bodily fear intensity, as well as latency to exhibit a fearful response, have been associated with maternal reports of infant fear as well as frontal electroencephalography (EEG) reactivity. While these measures have been used extensively since the introduction of Lab-TAB, they are typically averaged across the procedure, and differences between the four mask stimuli have not been sufficiently examined. This study addressed this gap in research by examining specific infant reactions, both behaviorally and from a neurophysiological standpoint, to each presentation of the fear-provoking stimuli to better understand factors that impact the expression of fear during this task. Our findings indicated significant differences in behavioral observations of distress and regulation, with the final/fourth mask eliciting stronger reactions; however, there were no such differences in the infants' neurophysiological response. Additionally, neither the fear subscale of the Infant Behavior Questionnaire-Revised (IBQ-R) nor the Negative Emotionality factor was predictive of infant's neurophysiological changes, distress, or regulation during the episode until examining subgroups based on age or sex. Further analyses of frontal alpha asymmetry across masks indicated that infants may become attuned to these stimuli over the course of the task, leading to less predictive utility than earlier neurophysiological markers. Results also revealed that older infants had differing neurophysiological reactions across the paradigm, whereas no significant differences were noted for younger infants. Finally, differences based on infant sex emerged with regard to temperament predictors of asymmetry. Implications of the discrepancy between results for the EEG asymmetry markers and observed distress/regulation in trial comparisons are discussed.