Figure 1.

Experimental design. A, A photograph of a tree shrew in the home cage. B, A schematic of the training procedure. C, The contrast discrimination task. The animal needs to choose the side that has a higher contrast gabor and report the choice by licking the corresponding port. D, Learning curve of individual animals. The y-axis is the response accuracy for the easiest condition on each day. Day 1 refers to the first day of training with two-sided gabor stimulus. Dashed gray line, 75% accuracy. Most animals reached this level by day 2 and all by day 7.