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Stimuli associated with less effort or with shorter delays to reinforcement are generally preferred over those associated with greater effort or longer delays to reinforcement. However, the opposite appears to be true of stimuli that follow greater effort or longer delays. In training, a simple simultaneous discrimination followed a single peck to an(More)
C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration(More)
A common procedure for studying the ability of animals to time is the peak procedure. With the peak procedure, animals are first trained on a fixed interval schedule (i.e., 30s). After the animals have been well trained on the fixed interval schedule, probe trials are introduced. On probe trials, the stimulus is presented longer (i.e., 90s) and the animal(More)
280 Evidence from human memory research indicates that humans can exert active control over the maintenance of memories. In studies involving " directed-forgetting " procedures , in which presentation of a list of items includes signals to remember some of those items but not others, humans show better memory for to-be-remembered items than for items that(More)
, has been used traditionally to show that humans can have active control over memory maintaining processes. Although several procedures have been used to demonstrate directed forgetting in humans, the one of most interest here is the " distinctive forget instruction " procedure (see Johnson, 1994). With this procedure , participants are given a list of(More)
Previous research suggests that when a fixed interval is interrupted (known as the gap procedure), pigeons tend to reset memory and start timing from 0 after the gap. However, because the ambient conditions of the gap typically have been the same as during the intertrial interval (ITI), ambiguity may have resulted. In the present experiment, the authors(More)
It has been shown in previous research [Kaiser, D.H., 2008. The proportion of fixed interval trials to probe trials affects acquisition of the peak procedure fixed interval timing task. Behav. Process., 77 (1), 100-108] that rats acquired peak responding sooner when fewer peak trials were presented during sessions of training with the peak procedure timing(More)
Divergent choose-absence retention functions typically found in pigeons following presence/absence-sample matching have been attributed to the development of a single-code/default coding strategy. However, such effects may result from adventitious differential responding to the samples. In Experiment 1, retention functions were divergent only when(More)
This study looked at the effects of neonatal cocaine exposure on activity rhythms over a 48-h period in rats. Subjects were artificially-reared from postnatal days (PN) 4-10 via intragastric cannulas. The four treatment groups included two cocaine doses (20 and 40 mg/kg per day), an artificially-reared control and a normally reared suckled control. Subjects(More)