Figure 1

Visual search displays.

In feature-conjunction trials, the target, a red apple, was presented amongst both same-colour and same-shape distractors. The total number of items defined the set size (9 and 5 are shown in panels a and b, respectively). In single-feature trials the target was presented amongst only a single distractor type and is therefore effortlessly found by virtue of its unique colour or shape (panel c). The search interval lasted 4 s, during which toddlers' gaze position and pupil dilation were monitored.