The development of laughter in the first year of life.
D000161:Acoustic Stimulation; D000367:Age Factors; D001307:Auditory Perception; D002657:Child Development; D003071:Cognition; D005106:Exploratory Behavior; D005239:Fear; D005260:Female; D006801:Humans; D007223:Infant; D007845:Laughter; D008297:Male; D010988:Play and Playthings; D011574:Psychoanalytic Theory; D012919:Social Behavior; D014110:Touch; D014796:Visual Perception