Sequence of events during a trial. Each trial began with an auditory prompt saying, “Let’s look for shape changes!” along with a fixation circle on the left or right side of the screen. The experimenter initiated the trial when the child was ready. The sample array then appeared on the screen for 2 s, followed by a blank interval of 1 s. The test array was then presented until the child verbally responded ‘match’ or ‘no-match’. The experimenter entered the child’s response on a keyboard. After a jittered inter-trial interval of either 1, 2, or 4 s, the next trial was presented on the other side of the screen. This example shows a ‘different’ trial at SS3 (the circle in the sample array changes to a plus-sign in the test array).