0 cm radius of the image. A behavior was considered to have ended when an infant looked away, initiated a different type of manual behavior, changed hands, or removed the hand (or hands). Uninterrupted repetitions of a given gesture type were counted as one instance of that categorical type of behavior. Thus, several uninterrupted repetitions of the same manual action were conservatively scored as a single behavior. We evaluated selleck the qualitative (“categorical”) types of manual exploration behaviors as well as the total number of behavior changes initiated in

sequence (“sequential”) for each display. In the Categorical level of analysis, infants’ manual gestures were classified as one of five gross categories of reaching behavior (e.g., touching, grasping, rubbing,

scratching, or patting). These qualitatively different types of reaching behaviors were recorded and tallied for each display. At the categorical level, infants could potentially receive a score between 0 and 5 representing the number of qualitatively different types of manual gestures initiated toward each display. In the Sequential level of analysis, a finer grain assessment of successive actions was reviewed. The total quantity of gesture changes that occurred in sequence were recorded and tallied for each display. Natural Product Library chemical structure For example, if an infant was observed rubbing a picture display with one hand followed by tapping with both hands, followed by rubbing with one hand, then those manual behaviors would be recorded as two categorical gestures and three Idelalisib cell line sequential gestures. For both measures of manual exploration, an impossible preference score was calculated for each infant by computing the total number of behaviors initiated toward the impossible cube divided by the sum of gestures

initiated to both the possible and impossible cube displays. Preference scores were then compared with 50/50 chance. We also documented the frequency of social referencing, vocalizations, and mouthing behaviors as independent and complementary measures of infants’ differential responses toward each type of display. Social referencing was defined as an occurrence of the infant looking to the parent or the experimenter only after the child had initially visually inspected the display at least once. Instances of social referencing were logged each time the child referred back to the parent/experimenter after viewing and/or touching the stimulus display. Social referencing behavior has been a useful indicator of infants’ perceptual judgments and impending actions during an ambiguous, uncertain situation involving novel or unusual stimuli (Klinnert, Emde, Butterfield, & Campos, 1986; Walden & Kim, 2005).