Anticipatory Eye Movements Reveal Infants’ Auditory and Visual Categories
Bob McMurray and Richard N. Aslin
Department of Brain and Cognitive Sciences, University of Rochester

We introduce a new paradigm for the assessment of auditory and visual categories in 6-month-old infants using a 2-alternative anticipatory eye-movement response. Infants were trained by 2 different methods to anticipate the location of a visual reinforcer at 1 of 2 spatial locations (right or left) based on the identity of 2 cuing stimuli. After a training phase, infants were presented with a series of generalization trials in which novel (untrained) stimuli served as the cue to the anticipatory eye movement. Four experiments illustrated that infants can learn the 2-choice discriminative response during training. Infants also showed anticipatory eye movements to novel stimuli, indicating sensitivity to variations along a variety of stimulus dimensions (e.g., color, shape, orientation, spatial frequency, pitch, and duration). In addition, the paradigm can be used to assess categorization in individual infants, thereby revealing the stimulus dimensions to which infants naturally attend.

Attention Getters
The following were used to break up training and testing (and to reengage the infant):
Attention 1
Attention 2
Attention 3

Experiment 3
The following four files are the stimuli for Experiment 3. Training stimuli are reinforced on the left or the right. The trajectory is predicted by the shape/color combination (e.g., red-square left; yellow-cross right). The following are training stimuli files:
RedSquareLeft
YellowCrossRight

Testing stimuli are not reinforced (the visual stimulus does not reemerge from behind the occluder). These files cross the shape/color dimensions from the training set. The following are testing stimuli files:
RedCross
YellowSquare

Experiment 4
The following six files are example stimuli for Experiment 4. Training stimuli are reinforced on the left or the right. The trajectory is predicted by the word (lamb left; teak right). The color of the visual stimulus is uncorrelated with the auditory stimulus and changes randomly from trial to trial (to maintain interest). The following examples of these stimuli are provided:
Lamb0_orange
Teak0_green

Testing stimuli are not reinforced (the visual stimulus does not reemerge from behind the occluder). The auditory tokens are the original words with a modified pitch or duration. As in the testing period, the color of the visual stimulus is nonpredictive and changes from trial to trial. The following examples of these stimuli are provided:
LambD1_orange
LambD2_orange
TeakP1_green
TeakP2_green