Figure 1. Schematic illustrations of the experimental apparatus and an alternating block stimulus.

A) The apparatus used in behavioural experiments. The ferret moved freely in the lower semicircular region of the arena. B) Example showing trials presented in alternating blocks of 8 trials with easy (blue) and hard (pink) detection conditions. Each block contains four no-sound trials and four sound trials (unfilled and filled squares, respectively), and two tones at two stimulus levels (dots, easy: s1, s2; hard: s3, s4). For blocks of 24 trials, there are 12 sound trials in a block, 6 at each of two levels.