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Your Eyes Say “No,” But Your Heart Says “Yes”: Behavioral and Psychophysiological Indices in Infant Quantitative Processing


should be sent to Caitlin C. Brez, Schiefelbusch Institute for Life Span Studies, 1000 Sunnyside Avenue, 1052 Dole Human Development Center, University of Kansas, Lawrence, KS 66045-7556. E-mail:


Behavioral indices (e.g., infant looking) are predominantly used in studies of infant cognition, but psychophysiological measures have been increasingly integrated into common infant paradigms. The current study reports a result in which behavioral measures and physiological measures were both incorporated in a task designed to study infant number discrimination. Seven-month-old infants were habituated to several sets of stimuli varying in object type, but of a constant numerical value (either two or three items). Although looking time to each of the test trials revealed no differences, differences in heart rate defined measures of attention revealed infants’ ability to discriminate number. These findings imply that the inclusion of indices other than behavioral measures should become commonplace in studies of infant cognition.