The role of "nothing" in memory for event duration in pigeons

The research reported herein is designed to test a signal detection account of the choose-short effect, which is the tendency of birds to report (afte r a long delay) that a short-duration sample was presented, regardless of w hether a short or long sample initiated the trial. According to the detecti on account, the choose-short effect arises because birds learn to selective ly search memory for evidence that the long sample appeared on a given tria l. This idea is tested, in part, by replacing short-sample trials with no-s ample trials and showing that performance is unaffected by this manipulatio n for birds exhibiting a choose-short effect. In addition, when no samples and long samples were associated with the same choice alternative (and the short sample was associated with the other alternative), birds were flexibl e enough to learn to respond on the basis of the presence Versus the absenc e of the short sample (and, as a result, a choose-long effect was observed) .