Figure 1.

Positive-reinforcement operant paradigm. A trial was initiated when the animal refrained from licking the waterspout for 0.5–1.0 s. A reference sound (non-target) was presented and repeated randomly one to five times after trial initiation. A target sound followed the reference sounds. When the ferret licked the waterspout within a 1.2 s response time window after target onset (the shaded target period), its response was counted as a hit, which was followed by water reward. If the ferret licked the waterspout within a corresponding time window after reference sound onset (the shaded reference period), its response was counted as a false alarm, which caused reduction in reward volume. A miss of the target lead to a 3–6 s timeout penalty after completion of the trial. A click sound was played as a secondary reward reinforcer after water reward delivery.