bjective: We use psychophysical methods to examine the maximum time intervals over which discrete events can be temporally integrated into the percept known as apparent motion. We hypothesized that the maximum time interval would be shorter in participants with attention deficit hyperactivity disorder (ADHD) than it would be in a control group. Method: Thirty-five adults with ADHD and 40 adult controls without ADHD participated in an apparent motion task, in which they viewed a stimulus flashing in 2 different locations and were asked to complete the trajectory of motion that they perceived. The stimulus flashes were separated by varied temporal intervals ranging from 200 to 2300 ms. Clear trajectory perception in this task indicates successful temporal integration. Results: At short intervals, we found evidence of clear trajectory perception in both groups, indicated by low variability in path estimations. At the longest intervals, neither group demonstrated path perception, evidenced by high variability in estimations. However, at intermediate intervals (1.7 s), the control group demonstrated path perception while the group with ADHD did not, indicating a difference between the 2 groups in the maximum interval over which apparent motion could be perceived. Conclusions: We suggest that ADHD is generally characterized by a contraction in the time scale governing the rate at which association strength decays. In contrast to theories that postulate general time-processing deficits, this work provides a precise sense in which temporality is disturbed in ADHD.
