Experimental design and procedure
The experimental design was identical to that in Experiment 1 except that children performed only
16 test trials in each block. The number of test trials was equal to that in other child studies (e.g., Duemmler
et al., 2008). We also reduced the reaching distance to 25 cm in the action task due to these
participants’ shorter arm lengths.
The procedure was the same as in Experiment 1 but with two exceptions. First, children had more
practice trials prior to the first experimental block. We provided them with the opportunity to practice
until they felt confident with the task. At the beginning of the training phase, we used Lego blocks to
familiarize children with the experimental setting. Second, we used the two response buttons as described
above. We asked each child to press a button with his or her right thumb if the rectangle was
narrow and to press a button with the left thumb if the rectangle was wide. These directions were reversed
for left-handed children to prevent a dominant hand effect.