Rats time long intervals: Evidence from several cases.

Long-interval timing fills the gap between the traditional range of short-interval timing (i.e., seconds to minutes) and the limited range of circadian entrainment (i.e., approximately a day). A number of reports suggest that rats time long intervals. However, a recent report proposed that anticipation of long, but noncircadian, intervals is highly constrained. We tested the hypothesis that long-interval timing is highly constrained by examining a number of cases: 7, 8, 9, 11, 12, and 13 hour intermeal intervals. We found evidence for long-interval timing in each case. Long-interval timing appears to be robust.