Figure 1
Experimental procedure. (A) Schematic of the moma condition. The matching and mismatching pairs were presented alternately in a block design. A baseline period, in which neutral shapes were accompanied by white noise, was inserted between the presentation of the matching and mismatching pairs. The experiment continued until the infants could not continue with the task. In each 6-s test block, infants were presented with three different spiky or three different round visual shapes, each followed by the novel word “moma”. The shapes and sounds were sound-symbolically matched (e.g., a round shape followed by “moma”) or mismatched (e.g., a spiky shape followed by “moma”). The duration of the baseline period was over 10 s, and varied across trials as the experimenter started the test trial only when the infant remained focused on the stimuli in the last 2 s. The presentation order of the matched and mismatched pairs was counterbalanced among infants. In the kipi condition, the visual stimuli were identical with the moma condition, except that the auditory stimulus was fixed as “kipi.” (B) The duration of each visual shape was 2 s in a sequence of the stimulus presentation. One of two nonsense word sounds, “kipi” or “moma,” was presented 200 ms after the onset of each visual shape (duration: 400 ms). The duration and timing of the onset of each visual and auditory stimulus in the baseline period was identical to that in the test block.
