Infant Response to Facelike Patterns Under Fixed-trial and Infant-control Procedures

10-week-old infants were shown 4 facelike patterns that differed along 2 dimensions: number of elements and the extent to which the elements were organized to resemble the human face. The purpose was to determine whether the stimulus dimension to which infants respond is different with fixed-trial than with infant-control methodologies. Each infant was tested under 1 of 3 experimental conditions: fixed trials (trials and intervals of fixed, predetermined durations), offset control (trial termination controlled by the behavior of the infant), or onset-offset control (trial initiation and termination both controlled by the infant's behavior). Although the relationship was linear with fixed trials and offset control but was curvilinear with onset-offset control, infants responded to number, rather than organization, of elements in all 3 conditions. Furthermore, no specific methodological advantages were demonstrated for infant-control procedures.