Figure 1.

Behavioural procedure. The sequence of events for each of the four stimuli. S1: short delay, small reward; S3: short delay, large reward; L1: long delay, small reward; and L3: long delay, large reward. The small reward consisted of one 2-s period of wheat reward, whereas the large reward consisted of three 2-s periods of wheat reward. The short delay and long delays were 2 s and 8 s in duration, respectively.