Preferential Looking Paradigm

The preferential looking paradigm is a foundational experimental method in infant research in which two visual stimuli are presented to an infant at the same time, side by side, and the amount of time the infant spends looking at each one is measured as an indirect but reliable indicator of what the infant can perceive, discriminate, or find more interesting, since infants cannot yet verbally report what they see or prefer. The psychologist Robert Fantz developed and popularized the technique beginning in the late 1950s and through the early 1960s, using a specially constructed looking chamber in which an observer, unseen by the infant, tracked the direction of the infant's gaze toward each of the paired images; Fantz's pioneering studies using the method demonstrated that even very young infants, including newborns only days old, reliably looked longer at patterned images, such as a simple drawing of a face, than at plain, unpatterned surfaces of matching brightness, overturning the earlier assumption that young infants perceive the visual world only as an undifferentiated blur. Because a significant, consistent preference for looking longer at one of two stimuli demonstrates that the infant is able to visually tell the two apart in the first place, the paradigm became a core tool for mapping out the developmental timeline of infant visual perception, including color vision, depth perception, and face recognition, and it directly inspired later, more sophisticated infant-testing methods, including the habituation procedure and Renee Baillargeon's violation-of-expectation paradigm.