Behavioural processes
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Behavioural processes · May 2013
On the joint control of preference by time and reinforcer-ratio variation.
Five pigeons were trained in a procedure in which, with a specified probability, food was either available on a fixed-interval schedule on the left key, or on a variable-interval schedule on the right key. In Phase 1, we arranged, with a probability of 0.5, either a left-key fixed-interval schedule or a right-key variable-interval 30s, and varied the value of the fixed-interval schedule from 5s to 50s across 5 conditions. In Phase 2, we arranged either a left-key fixed-interval 20-s schedule or a right-key variable-interval 30-s schedule, and varied the probability of the fixed-interval schedule from 0.05 to 1.0 across 8 conditions. ⋯ The results are discussed in terms of reinforcement effects, timing in the context of alternative reinforcers, and generalized matching. These results can be described by a quantitative model in which reinforcer rates obtained at times since the last reinforcer are distributed across time according to a Gaussian distribution with constant coefficient of variation before the fixed-interval schedule time, changing to extended choice controlled by extended reinforcer ratios beyond the fixed-interval time. The same model provides a good description of response rates on single fixed-interval schedules.
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Behavioural processes · Sep 2012
Functional analysis of concealment: a novel application of prospect and refuge theory.
According to prospect-refuge theory, humans prefer environments that afford protection from threat (refuge), but also provide large fields of view (prospect). Prospect-refuge theory in the past has traditionally only been applied to humans, but many of the same contingencies governing spatial preference ought to also hold true in animals. The focus of this study was to examine if this phenomena also occurs in animals. ⋯ A simulated predator was released during the trial to examine how contextual factors may influence the degree of prospect and refuge preferred. The results indicate a preference for the enclosed refuge at stimulus onset even though this was not reflective of what happened prior to predator release. The results suggest spatial preferences in animals are influenced by prospect-refuge considerations in certain contexts.
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Behavioural processes · May 2010
An effect of inter-trial duration on the gambler's fallacy choice bias.
The gambler's fallacy is defined as the avoidance of a winning outcome in a stochastic environment with a constant probability. We tested the possibility that the gambler's fallacy in humans is responsive to the amount of time between choice allocations. Two groups of subjects were placed in a six-choice betting game in which the choices were clustered into two "patches." Groups were defined by the length of time - 2s or 6s - between trials. ⋯ This difference was found primarily to be due to differences in the number of subjects showing an opposing bias to the gambler's fallacy, namely a preference for the most recent winning alternative. This choice bias is termed the hot hand fallacy. Our findings contradict predictions derived from a foraging heuristic and from traditional accounts of the gambler's fallacy.
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Six pigeons responded on a four-key concurrent variable-interval schedule in which a 27:9:3:1 distribution of reinforcers between the keys changed every 10 reinforcers. Their behaviour quickly came under the control of this changing four-way reinforcer ratio. However, preference between a pair of keys depended not only on the relative reinforcer rates on those keys, but also on the absolute levels of those rates. ⋯ Despite accurate tracking of the reinforcer ratio, reinforcers obtained late in components and from leaner keys still produced strong pulses, suggesting both extended and local control of behaviour. Patterns of switching between keys were graded and similarly controlled by the reinforcer rates on each key. Whether considered in terms of switching, local preference pulses, or extended preference, behaviour was controlled by a rapidly changing four-way reinforcer ratio in a graduated, continuous manner that is unlikely to be explained by a simple heuristic such as fix-and-sample.