On the Clock: Interval Timing and Overshadowing in Domestic Dogs (Canis familiaris)
Interval timing is an important skill that allows animals to approximate how much time has elapsed since a given event. Little, however, is known about interval timing in domestic dogs. In an initial experiment, dogs were trained to make an operant response on 30-s fixed intervals, with either a light or a tone + light compound signaling the beginning of the fixed interval. When dogs in the compound group were subsequently tested with nonreinforced 60-s tone-only probe trials, the dogs’ rate of responding peaked near 30 s. When the same dogs were tested with light-only probes, however, no evidence of timing was found. In a second experiment, a bisection task was used in which dogs had to learn to approach 1 feeder when given an 8-s tone + light signal, and another feeder when given a 2-s tone + light signal. When subsequently tested at intermediate durations, psychophysical curves showed clear control of timing by the tone stimulus but not by the light stimulus. These findings clearly demonstrate that dogs are able to time fixed intervals and show the existence of an overshadowing effect, in which dogs are able to time a light cue presented alone but do not attend to the light when it is presented simultaneously with a tone.