The perception of empty and filled time intervals by rats

Area of Science:

• Behavioral Neuroscience
• Animal Cognition
• Psychophysics

Background:

• Temporal perception is crucial for many behaviors.
• Investigating interval timing in rodents provides insights into conserved neural mechanisms.
• The 'filled interval illusion' describes the subjective lengthening of time for intervals containing stimuli.

Purpose of the Study:

• To investigate the 'filled interval illusion' in rats.
• To determine if rats perceive filled intervals as longer than empty intervals of the same duration.
• To explore potential mechanisms underlying this illusion, such as clock rate or switch latency.

Main Methods:

• Rats were trained using a within-subjects design to discriminate durations of filled and empty intervals.
• Psychophysical testing employed three sets of anchor durations.
• Ambient conditions were manipulated in a second experiment to assess their influence on timing.

Main Results:

• Rats exhibited more 'long' responses for filled intervals compared to empty intervals.
• Filled intervals were timed more precisely and perceived as longer than empty intervals.
• Ambient conditions did not significantly affect interval timing, ruling out a simple sensory artifact.

Conclusions:

• These findings provide the first clear evidence of a filled interval illusion in rats.
• The results suggest the illusion may be mediated by a faster internal clock rate during filled intervals.
• This challenges explanations solely based on slower switch latencies for empty intervals.