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Factors That Affect Local Choice and Temporal Discrimination |
Monday, May 27, 2013 |
3:30 PM–4:50 PM |
101 G (Convention Center) |
Area: EAB; Domain: Basic Research |
Chair: Sarah J. Cowie (University of Auckland, New Zealand) |
Discussant: Federico Sanabria (Arizona State University) |
Abstract: When responding is examined as a function of time since the offset of a time marker, timing can be explored in either discrete-trial procedures or in free-operant procedures. In discrete-trial preparations, following a period of training where reinforcement is consistently delivered at a fixed time (t) since a time marker, response maxima in trials where no reinforcement is presented occurs approximately at t. In free-operant procedures where food deliveries act as time markers, varying degrees of control by the changing probabilities of food across time are observed. Decaying control by time can be reinstated by stimuli that signal specific aspects of the local contingency. The present symposium explores the factors that moderate control by time elapsed since a time marker, and addresses questions derived from theories and models of choice and timing, including: 1) Can time since food delivery act as a discriminative stimulus for the future likelihood and key-location of food? 2) Is control by time since food delivery enhanced when changes in the contingencies of food occur rapidly or gradually? 3) What role do temporal stimuli have in enhancing control by local food ratios in free-operant procedures? 4) Does trial length and relative reinforcer rate affect time discrimination? |
Keyword(s): local choice, modelling, signaling, timing |
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The Effects of Mapped and Unmapped Temporal Stimuli on Local Choice |
LUDMILA MIRANDA DUKOSKI (University of Auckland, New Zealand), Michael C. Davison (University of Auckland, New Zealand), Douglas Elliffe (University of Auckland, New Zealand) |
Abstract: Pigeons worked on an extension of an experiment where the local probability of food on two concurrently available keys varied sinusoidally as a function of time since food delivery. Prior conditions had shown that the extent to which preference within inter-food intervals was controlled by locally-changing food probabilities was affected by: first, the number of transitions from high left-food probability to high right-food probability over 60 s and, second, the arrangement of stimuli arranged to signal the temporal properties of the task. In the present set of conditions, we investigated the function of the temporal stimuli further. Specifically, we asked whether two stimuli per 60-s intervals, which were always associated with an 8-s portions of the sinusoidal variation, would better function as time markers if they were both associated with the same portion of the sinusoidal variation. Additionally, we examined the effects on local choice of stimuli that signaled different portions of the sinusoid. Generally, local choice within stimulus presentations followed the local food probabilities well irrespective of whether the stimuli were associated with the same or different portion of the sinusoidal variation in local food probabilities. However, an effect of the latter arrangement of stimuli was observed on choice immediately following food delivery. |
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Discriminating the Time of Local Food-Ratio Reversals |
SARAH J. COWIE (University of Auckland, New Zealand), Michael C. Davison (University of Auckland, New Zealand), Douglas Elliffe (University of Auckland, New Zealand) |
Abstract: On concurrent exponential variable-interval schedules in which the relative frequency of food deliveries for responding on the two alternatives reversed at a fixed time after each food delivery, the point of food-ratio reversal was varied from 10 s to 30 s, and the overall reinforcer rate was varied from 1.33 to 4 per minute, across conditions. The effect of rate of food delivery and food-ratio reversal time on choice and response rates was small. In all conditions, post-food choice was toward the pre-reversal-richer key, regardless of the last-food location. Unlike the local food ratio, which changed in a stepwise fashion, local choice changed according to a decelerating monotonic function, so that after the first few time bins, the local response ratio was substantially less extreme than the local food ratio. This deviation in choice appeared to result from the birds inaccurate discrimination of the time of food deliveries; choice was enhanced by stimuli that increased the discriminability of the time of step change, and was well-described by a model which redistributed obtained food ratios across surrounding time bins. |
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Response Resurgence in the Peak Procedure |
LEWIS A. BIZO (University of Waikato, New Zealand), Rachael Anne Lockhart (University of Waikato, New Zealand), Mark McHugh (University of Waikato, New Zealand), Christopher D. Stanley (University of Waikato, New Zealand), Mary Foster (University of Waikato, New Zealand), James McEwan (University of Waikato, New Zealand) |
Abstract: In three separate experiments the timing abilities of brush tail possums and domestic hens on the peak procedure was investigated. This procedure involved animals responding on two trial types within an experimental session. On some trials responding was reinforced according to a Fixed Interval (FI) schedule (in effect on 80% of trials), and on other 20% trials, Peak Interval (PI) trials, responding was not reinforced with food. Possums lever pressed, and hens key pecked, for food reinforcers on different FI schedules, and the duration of the PI was varied across a range. Response rates typically increased to a maximum at about the time the responses were normally reinforced and then decreased after the time that food would normally be reinforced, before increasing again towards the end of the PI regardless of the duration of the PI trial if that duration was fixed. When the PI was of variable rather than fixed duration, however, the rate of responding on PI trials decreased towards the end of the PI. When relative response rates were plotted as a function of relative time the function typically superposed for the ascending, but not descending portions of the function. The results are discussed in terms of Webers law, and various quantitative models timing. |
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