Fig. 3.

Long-lasting memory benefits of the early reward. Shown are the mean difference scores for baboons (A) and pigeons (B) during postlearning memory presentations (trial presentations 20- 65) as categorized by whether the initial first presentation for all trials was positively reinforced or punished. Positive values indicate that the rewarded pictures supported higher accuracy than those initially punished. This reward advantage was estimated to last at least 6 months in the pigeons and 8 months in the baboons, as determined by adjusting the number of presentations by the average time interval between these memory trials over the course of the experiment. Mean old-item accuracy over this time period (B03 = 76%, B09 = 75%, BF = 78%, Linus = 75%).