Transference effects of prior non-contingent reinforcement on the acquisition of temporal control on fixed-interval schedules.

In two experiments we examined the influence of response and time factors on the speed of acquisition of temporal control on FI schedules. In Experiment 1, prior exposure to FT accelerated the development of temporal control on FI schedules of the same temporal value. It was also found that the slower acquisition on FI with prior RT was similar to that of rats with prior standard training. In Experiment 2, prior exposure to FT accelerated the development of temporal control on a FI schedule with a threefold increase in temporal value. Additionally, it was found that with prior FI 30s training, acquisition of temporal control on FI 90s was even faster than with prior FT 30s. Measures of head-entries into the feeder along the experiments indicated that temporal control was already developed during the periodic but not during the non-periodic histories and that this control transferred to lever press during FI testing phase.

Influencia del tempo de la música en las emociones / Influence of music tempo on emotion

Se sabe que la música puede influir en dos componentes de las emociones: el arousal y la valencia. En particular, se ha reportado que el tempo o rapidez de la música está directamente relacionado con el arousal, aunque su relación con la valencia o medida de afecto no es aún clara. En este trabajo se analizó la influencia del tempo en ambos componentes mediante la exposición de 24 estudiantes de licenciatura a treinta extractos musicales de distinto tempo. Además se evaluó la posible modulación de la relación tempo-valencia por el rasgo de personalidad extroversión/introversión. Los resultados confirmaron la influencia del tempo sobre el arousal, pero no sobre la valencia, así como una posible mediación de la dimensión de personalidad introversión-extroversión sobre la valencia.

Arousal and valence, two main components of emotion, are known to be influenced by music. Particularly, some studies have shown a positive relationship between tempo (music speed) and arousal, but no conclusive evidence about tempo and valence relationship has been found. In this experiment, the effect of tempo on both arousal and valence was studied.Twenty four undergraduate students were exposed to 30 musical excerpts with different tempo. In addition, the possible mediation of the extraversion-introversion personality trait on the relationship tempo-valence was also determined. The results confirmed the effect of tempo on arousal but not on valence, and a mediating effect of introversion-extraversion personality dimension on valence.

The effect of stimulus discriminability on strategies for learning multiple temporal discriminations.

The goal was to identify training conditions under which temporal intervals that are signaled by different stimuli are memorized (i.e., the temporal behavior is readily shown to be under stimulus control). Undergraduate students were trained on three signaled temporal discriminations using a peak procedure. The intervals were trained in either blocks of trials or with trials intermixed within the session, and then they were given a transfer test with intermixed trials. There were two levels of stimulus discriminability, defined by the similarity of the stimuli. Most participants memorized the intervals when the discriminations were intermixed within the session, or were easy, but not when the discriminations occurred in blocks and were difficult. In the transfer tests, those participants trained in the difficult discrimination that occurred in blocks of trials typically continued to perform as they did during the last-trained interval, regardless of the stimulus presented. These results are better explained by a memory retrieval than a memory storage account.

Performance of spontaneously hypertensive rats in a peak-interval procedure with gaps.

The purpose of the present experiment was to evaluate timing behavior in spontaneously hypertensive rats (SHR), and compare it to the performance of Wistar Kyoto (WKY), and Wistar (WI) rats. In the first phase of the experiment, the subjects were exposed to a peak-interval procedure, in which fixed-interval 30s trials were alternated with nonreinforced and extended (peak) trials. After 60 sessions, an approximation to a Gaussian probability density function was fitted to the response rate during peak trials in order to estimate the peak time, the peak rate and the Weber fraction. The results showed no difference among the strains in the peak time and the Weber fraction, but a higher peak rate in SHR. In the second phase of the experiment, a gap procedure was introduced; in 80% of the peak trials the stimuli associated with the fixed interval and peak trials were turned off for 9s. Gap trials produced peak time shifts that were longer than those expected if the clock had stopped during the gap but shorter than those had the clock been reset, and no significant differences between the strains were found. Given the great importance that different theories give to temporal processing in the development of the main symptoms of attention deficit hyperactivity disorder (ADHD), and the existence of time perception deficits in humans with ADHD, the present results question the validity of SHR as an animal model of that disorder, and suggest the necessity of exploring the timing behavior of other animal models of ADHD.

Effects of reinforcement history on response rate and response pattern in periodic reinforcement.

Several researchers have suggested that conditioning history may have long-term effects on fixed-interval performances of rats. To test this idea and to identify possible factors involved in temporal control development, groups of rats initially were exposed to different reinforcement schedules: continuous, fixed-time, and random-interval. Afterwards, half of the rats in each group were studied on a fixed-interval 30-s schedule of reinforcement and the other half on a fixed-interval 90-s schedule of reinforcement. No evidence of long-term effects attributable to conditioning history on either response output or response patterning was found; history effects were transitory. Different tendencies in trajectory across sessions were observed for measures of early and late responding within the interreinforcer interval, suggesting that temporal control is the result of two separate processes: one involved in response output and the other in time allocation of responding and not responding.