The choose-short and choose-long effects may depend on interval consistency and similarity.

The present study examined the effects of varying the events occurring during the delay interval (DI) and the intertrial interval (ITI) on asymmetries in temporal discrimination in pigeons. Four groups were exposed to combinations of equal or different events during DIs and ITIs and consistent or inconsistent arrangements between short-sample and long-sample trials. Results showed that differentiating short from long samples shortened acquisition time and eliminated asymmetries in performance. The specific form of performance depended on the interaction between interval similarity and task arrangement: Equal intervals with consistent arrangements produced a choose-short effect, whereas different intervals with consistent arrangements produced a choose-long effect. Inconsistent arrangements led to symmetrical performance, either stable or decreasing as the DI increased. These findings indicate that asymmetries in temporal discrimination under delayed matching-to-sample procedures depend not on memory mechanisms such as code loss or subjective shortening, but on how the organization of task events within the delay and intertrial intervals enhances or reduces stimulus control. The study thus supports interpreting temporal discrimination in this class of procedures as a problem of stimulus control shaped by the task's event structure rather than by memory decay.