Eye-trackers suitable for use with infants are now marketed by several commercial vendors. As eye-trackers become more prevalent in infancy research, there is the potential for users to be unaware of dangers lurking "under the hood" if they assume the eye-tracker introduces no errors in measuring infants' gaze. Moreover, the influx of voluminous…

Since the mid-1800s, experimental psychologists have been using eye movements and gaze direction to make inferences about perception and cognition in adults (Muller, 1826, cited in Boring, 1942). In the past 175 years, these oculomotor measures have been refined (see Kowler, 1990) and used to address similar questions in infants (see Aslin, 1985,…