Valuing the future at different temporal points: The role of time framing on discounting.

The rate of delay discounting exhibited by individuals has been experimentally altered by manipulating the way in which time is described, a specific application of the framing effect. Previous research suggests that using specific dates to describe delays tends to lower temporal discounting and change the shape of the discounting function. The main purpose of this study was to assess the influence of framing on discounting in different temporal contexts.

Similar attention and performance in female and male CD1 mice in the peak procedure.

Inaccurate and distorted timing are associated with neurodegenerative disorders such as Alzheimer's disease and schizophrenia in humans, which generates interest in the discovery and understanding of the factors behind such timing difficulties. Timing research in mice has taken an important role, because the availability of genetically-altered strains allows establishing the causal role of specific genes on such neurodegenerative disorders. Nevertheless, few studies have considered mice's sex and some have found sex differences in timing, although results are not yet conclusive.

Uncontrollable chronic stress affects eating behavior in rats.

The issue of whether the decrease in food intake induced by inescapable shock is due to the uncontrollability of the stressor or the shock per se has not yet been settled. Besides, whether food intake is differentially affected by an uncontrollable chronic stressor has been explored only by a few studies. Thus, we evaluated the effects of chronic escapable or inescapable electric shocks on eating behavior.

Toward a Unifying Account of Impulsivity and the Development of Self-Control.

Impulsivity has traditionally been thought to involve various behavioral traits that can be measured using different laboratory protocols. Whereas some authors regard different measures of impulsivity as reflecting fundamentally distinct and unrelated behavioral tendencies (fragmentation approach), others regard those different indexes as analogue forms of the same behavioral tendency, only superficially different (unification approach). Unifying accounts range from mere intuitions to more sophisticated theoretical systems.

Reinforcement value and fixed-interval performance.

The concept of reinforcement value summarizes the effect of different variables, such as reinforcement delay, reinforcement magnitude, and deprivation level, on behavior. In the present set of experiments, we evaluated the effect of reinforcement devaluation on performance under FI schedules. The literature on timing and reinforcement value suggests that devaluation generates longer expected times to reinforcement than the same intervals trained under control conditions.

The absence of numbers to express the amount may affect delay discounting with humans.

Human delay discounting is usually studied with experimental protocols that use symbols to express delay and amount. In order to further understand discounting, we evaluated whether the absence of numbers to represent reward amounts affects discount rate in general, and whether the magnitude effect is generalized to nonsymbolic situations in particular. In Experiment 1, human participants were exposed to a delay-discounting task in which rewards were presented using dots to represent monetary rewards (nonsymbolic); under this condition the magnitude effect did not occur.

Training a new response using conditioned reinforcement.

Some of the most frequently used methods in the study of conditioned reinforcement seem to be insufficient to demonstrate the effect. The clearest way to assess this phenomenon is the training of a new response. In the present study, rats were exposed to a situation in which a primary reinforcer and an arbitrary stimulus were paired and subsequently the effect of this arbitrary event was assessed by presenting it following a new response.

Learned helplessness in the rat: effect of response topography in a within-subject design.

Three experiments investigated learned helplessness in rats manipulating response topography within-subject and different intervals between treatment and tests among groups. In Experiment 1, rats previously exposed to inescapable shocks were tested under an escape contingency where either jumping or nose poking was required to terminate shocks; tests were run either 1, 14 or 28 days after treatment. Most rats failed to jump, as expected, but learned to nose poke, regardless of the interval between treatment and tests and order of testing.

Variation, repetition, and choice.

Experiment 1 investigated the controlling properties of variability contingencies on choice between repeated and variable responding. Pigeons were exposed to concurrent-chains schedules with two alternatives. In the REPEAT alternative, reinforcers in the terminal link depended on a single sequence of four responses.