The image-scratch paradigm: a new paradigm for evaluating infants' motivated gaze control.

Human infants show spontaneous behaviours such as general movement, goal-directed behaviour, and self-motivated behaviour from a very early age. However, it is unclear how these behaviours are organised throughout development. A major hindrance to empirical investigation is that there is no common paradigm for all ages that can circumvent infants' underdeveloped verbal and motor abilities. Here, we propose a new paradigm, named the image-scratch task, using a gaze-contingent technique that is adaptable to various extents of motor ability. In this task, participants scratch off a black layer on a display to uncover pictures beneath it by using their gaze. We established quantitative criteria for spontaneous eye-movement based on adults' gaze-data and demonstrated that our task is useful for evaluating eye-movements motivated by outcome attractiveness in 8-month-olds. Finally, we discuss the potential of this paradigm for revealing the mechanisms and developmental transitions underlying infants' spontaneous and intentional behaviours.