Does time-shrinking take place in visual temporal patterns?

The duration of a short empty time interval (typically shorter than 300 ms) is often underestimated when it is immediately preceded by a shorter time interval. This illusory underestimation--time-shrinking--had been studied only with auditory temporal patterns. In the present study, we examined whether similar underestimation would take place with visual temporal patterns. It turned out that underestimation of the same kind takes place also in the visual modality. However, a considerable difference between the auditory and the visual modalities appeared. In the auditory modality, it had been shown that the amount of underestimation decreased for preceding time intervals longer than 200 ms. In the present study, the underestimation increased when the preceding time interval varied from 160 to 400 ms. Furthermore, the differences between the two neighbouring intervals which could cause this underestimation had always been in a fixed range in the auditory modality. In the visual modality, the range was broader when the intervals were longer. These results were interpreted in terms of an assimilation process in light of the processing-time hypothesis proposed by Nakajima (1987 Perception 16 485-520) in order to explain an aspect of empty-duration perception.     

Further Evidence for Swimming-Based Pica in Rats

Aberrant pica behavior (i.e., kaolin clay ingestion) has been regarded as a behavioral marker of nausea in rats that cannot vomit because of anatomical and/or neural reasons. The previous study reported that a single swimming session of 40 min generated pica behavior, implying that swimming induces nausea in rats. However, the rats tested in that report were not experimentally naive. The present study successfully replicated swimming-based pica with experimentally naive rats (Experiment 1). It also showed that pica was observed with pool confinement of 20 min but not with that of 10 min (Experiments 2A and 2B) and that roaming in shallow water did not generate pica (Experiment 3). These results taken together suggest that swimming for at least 20 min induces nausea in rats, implying that rats’ taste aversion learning based on swimming is mediated by gastrointestinal discomfort.     

Does Conspecific Fighting Yield Conditioned Taste Aversion in Rats?

Running in an activity wheel yields conditioned aversion to a taste solution consumed before the running, but its underlying physiological mechanism is unknown. According to the claim that energy expenditure or general stress caused by physical exercise is a critical factor for this taste-aversion learning, not only running but also other stressful exercises should yield conditioned aversion to the paired taste. This prediction was disconfirmed in two experiments, because stressful conspecific fighting did not work as an effective agent to establish taste aversion in rats.