Figure 1.

Video stimuli and probes. (A) Mothers of infant participants were instructed to answer a series of questions with both a neutral and smiling expression. Sound was removed from the videos, and 16 video clips of each emotion were combined to achieve a 32 s stimulus with transition from neutral to smiling expression. Stranger videos were selected for similarity in appearance to the mother. A visual baseline of moving objects was used to direct infant attention to the screen at the beginning of the experimental session, and a fixation cross was present between stimulus presentation. (B) Two chevron arrays of probes placed into a custom designed neoprene cap. Probes were placed in the frontal and right lateral panels, and adjusted to proper fit and location with the colored Velcro tabs.