Fig. 3.

Mean (±SEM) cumulative number of training sessions (during phase 3 training) necessary for a group of rats (n = 5) to reach criterion at each progressively more difficult aperture setting. Each data point represents a different step in the sequence (see Materials and Methods, Fine-grained distance detection). The first data point (Aperture Difference of 33 mm) corresponds to aperture settings of 85 mm (wide) and 52 mm (narrow). The final data point (Aperture Difference of 3 mm) corresponds to aperture settings of 62 and 65 mm. Rats rapidly learn to perform the discrimination, and they are capable of accurately discriminating between apertures that are very similar in width.