Figure 2.

On each trial, participants fixated the centre of a display where a digit (1–9, 5 excluded) appeared for 1,300 ms. In half the blocks, digits were classified as smaller/larger than five in the other half as even/odd. Participants responded with either their right index and middle finger or their left index and middle finger, and the experiment was divided in two main parts according to which hand was used to respond. Since nine is large in the experimental range, the right-side key is compatible with a left-to-right representation of the numbers 1–9, and the left-side key is incompatible.