Recently, several studies have claimed that soon after their first birthday infants understand others' false beliefs. However, some have questioned these findings based on criticisms of the looking-time paradigms used. Here we report a new paradigm to test false belief understanding in infants using a more active behavioral response: helping.…

Five experiments examined 15- and 18-month olds' sensitivity to morphosyntactic dependencies. Results indicated that 18-month olds, but not 15-month olds, were sensitive to basic relationship between "is" and "-ing" and that 18-month-olds could track relationships between functor morphemes. Findings were consistent with hypothesis that 18-month…

Two studies investigated development of infants' visual preferences for the human body shape. Results indicated that 18-month-olds had a reliable preference for scrambled body shapes over typical body shapes in line drawings, while 12- and 15-month-olds did not respond differentially. In condition using photographs, only 18-month-olds had reliable…

Three habituation experiments examined the necessary conditions under which infants invoked the principle of rational action, interpreting behavior as goal-directed action. Found that the rational action principle operated at 9 months but not at 6 months. Perceptual cues indicating agency were not necessary prerequisites for a goal-directed…

Three experiments used a visual fixation technique to examine whether toddlers interpret speech continuously. Found that 24-month-olds had delayed responses when a competing distractor picture's label overlapped phonetically with the target at onset, but not when the pictures' labels rhymed, showing that children monitored speech stream…

Five experiments used a categorization habituation-of-looking paradigm to investigate infants' categorization of animals and vehicles based on static versus dynamic attributes of stimuli (color images versus dynamic point-light displays). Findings showed that 6-month-olds categorize animals and vehicles based on static and dynamic information, and…

Two experiments examined development of the ordinality concept in infants. Found that 11-month-olds successfully discriminated, whereas 9-month-olds failed to discriminate sequences that descended in numerical value from sequences increasing in numerical value. Nine-month-olds could discriminate the ordinal direction of sequences that varied in…

Examined in four studies whether and when infants connect information about an actor's affect and perception to their action. Found that 12-month-olds, but not 8-month-olds, recognized that an actor was likely to grasp the object she had visually regarded with positive affect. Replicated findings with 12- and 14-month-olds and with several…