CHOICE BEHAVIOR IN GAME PLAYING SITUATIONS AS A FUNCTION OF AMOUNT AND PROBABILITY OF REINFORCEMENT.
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The role of medial shell of the nucleus accumbens in acquisition of spatial behavior was studied in rats performing choice task in radial maze with asymmetrical water reinforcement. It has been found that the nucleus accumbens lesioned rats failed in finding larger rewards but preserve their reward-seeking behavior guided by visual discriminative stimuli. The results obtained are in good agreement with suggestion that the nucleus accumbens is a site of convergence of spatial information (from hippocampus) with reward information (from amygdala and VTA), providing bridge for effective limbic-motor interface underlying motivated goal-directed behavior in animals.
Animals process sensory information according to specific computational rules and, subsequently, form representations of their environments that form the basis for decisions and choices. The specific computational rules used by organisms will often be evolutionarily adaptive by generating higher probabilities of survival, reproduction, and resource acquisition. Experiments with enclosed colonies of bumblebees constrained to foraging on artificial flowers suggest that the bumblebee's cognitive architecture is designed to efficiently exploit floral resources from spatially structured environments given limits on memory and the neuronal processing of information. A non-linear relationship between the biomechanics of nectar extraction and rates of net energetic gain by individual bees may account for sensitivities to both the arithmetic mean and variance in reward distributions in flowers. Heuristic rules that lead to efficient resource exploitation may also lead to subjective misperception of likelihoods. Subjective probability formation may then be viewed as a problem in pattern recognition subject to specific sampling schemes and memory constraints.
The purpose of the present study was to systemically test the hypothesis that older people adopt risk-avoiding strategies when faced with risky-choice situations. Ninety-six adults, representing four age cohorts, filled out a risk-taking questionnaire consisting of twelve situations demanding a choice between a safe and a risky option. One-half of the choices involved potential losses, the other half involved potential gains. The results indicated that older adults choose no more safe alternatives than do younger adults. Additionally, for all age cohorts, risk avoiding was more evident when choices were between risky and certain gains than when choices were between risky and certain losses. This pattern of responding suggests that older adults do not necessarily adopt a general strategy of avoiding risk options when a safe alternative is available. Instead, risk avoiding, for all age cohorts, appears to be influenced by the parameters of the choice situation.
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The hypothesis that endogenous opioid peptides modulate attentional processes was tested. The effects of the opioid antagonist naltrexone (NALT), d-amphetamine (AMP), and their interaction were investigated in rats trained in a two-choice task in which the position of a short-duration light served as a cue for food-reinforced responses. NALT (0.25, 1.0, 5.0, and 10.0 mg/kg) produced no significant changes in performance (accuracy, choice latency, and food retrieval time). As predicted, AMP induced dose-dependent biphasic effects. Low doses of AMP (0.25 and 0.5 mg/kg) significantly enhanced accuracy, decreased choice latency, and lengthened food retrieval time; 1.25 mg/kg AMP disrupted accuracy, increased choice latency, and further lengthened food retrieval time. The combination of NALT (0.25, 1.0, and 10.0 mg/kg) and subthreshold doses of AMP (0.07 and 0.1 mg/kg) had no effect on performance except for an increase in food retrieval time with 10.0 mg/kg NALT, whereas the combination of NALT and moderate doses of AMP (0.5 and 1.0 mg/kg) disrupted accuracy, increased choice latencies, and lengthened food retrieval time. These results do not support the hypothesis that endogenous opioid peptides play a vital role in attentional processes or that opioid antagonists may be useful in the treatment of attentional deficit disorders.
Rhesus monkeys were allowed to choose between intravenous injections of cocaine and food reinforcement for lever pressing. A choice trial was available every 15 minutes continuously for 8 days. The animals chose cocaine almost exclusively, which resulted in high cocaine intake, decreased food intake, weight loss, and marked behavioral toxicity. The study provides evidence of the reinforcing efficacy of cocaine.
Swimming and the whole-body shortening reflex are two incompatible behaviors performed by the medicinal leech Hirudo medicinalis. We set out to examine the neuronal basis of the choice between these behaviors, taking advantage of the fact that the neuronal circuit underlying swimming is relatively well understood. The leech swim circuit is organized hierarchically and contains three interneuronal levels, including two upper levels of "command-like" neurons. We tested the responses of the swim circuit neurons to stimuli that produced shortening, using reduced preparations in which neurophysiological recording could be performed while behaviors were elicited. We found that the majority of the swim circuit neurons, including most of the command-like cells and all of the cells at the highest hierarchical level of the circuit, were excited by stimuli that produced shortening as well as by stimuli that produced swimming. Only a subset of neurons, at levels below the top, were inhibited during shortening; these included one of the command-like cells and an oscillator cell (an interneuron that is part of the central pattern generator for swimming). These results imply that the control of the choice between swimming and shortening is not exercised selectively at the higher levels of the swim circuit.
The interaction of food-based memories and food-event outcome expectancies in pigeons was assessed using a simultaneous, delayed-symbolic-matching-to-sample procedure. The components of the compound sample were presented in sequence, and consisted of a food-based event (food or no-food) followed by a color cue (red or green). Choice of a pattern of horizontal lines was "correct" following presentation of the red cue, while choice of a vertical line pattern was "correct" after green. In all but a control condition, the food-based event with which a trial began, or the food-event outcome with which a trial concluded, or both, were also correlated with the correct pattern. Of particular interest was the relative accuracy of two groups for whom both memories and expectancies were correlated with the correct choice-pattern. For one group, the memories and expectancies corresponding to the pre- and postchoice food-related events were similar, whereas for the other they were dissimilar. Outcome expectancies supported a higher level of performance than food-based memories, and subjects with both outcome expectancies and food-based memories chose more accurately than those with memories or expectancies only. In addition, subjects with dissimilar food-based memories and outcome expectancies chose more accurately than those with similar memories and expectancies. The implications of the above findings for the nature of event representation in pigeons are discussed.
The time course of serum concentration and performance on a concurrent probability matching task were evaluated in normal adults receiving 0.15 or 0.3 mg/kg of methylphenidate. The behavioral task, an arcade-like problem-solving game, revealed that drug-treated subjects improved their performance upon repeated testings during pharmacokinetic evaluation at a lower rate than did non-treated controls over the same time span. However, drug-treated subjects failed to adopt the adaptive problem-solving strategies selected by controls.
Spatial memory of rats was examined in two types of radial mazes in which animals had to obtain food from 6-, 8-, or 12-different arms without repeating choices. In Maze 1 with tubular channels closed at the far end rats returned to the central platform by backing out from the just visited alley. In Maze 2 the tubular channels were equipped with one-way doors at both ends and the central platform was raised 5 cm above the floor. Rats leaving the far end of the alley returned to the central platform through a circular hole in its center. Performance was almost perfect in both apparatuses, but rats preferred to enter adjacent alleys in Maze 1 and widely separated alleys in Maze 2. These behaviors were significantly different from computer-simulated random choice from the set of correct solutions of the task. It is concluded that Maze 2 is better suited for repeated experiments with the same animal because the obligatory return to the center of the platform precludes the simplification of the task by response chaining.
This paper presents a dynamic generalization of a model often used to aid marketing decisions relating to conventional products. The model uses stated-preference data in a random-utility framework to predict adoption rates for new pharmaceutical products. In addition, this paper employs a Markov model of patient learning in drug selection. While the simple learning rule presented here is only a rough approximation to reality, this model nevertheless systematically incorporates important features including learning and the influence of shifting preferences on market share. Despite its simplifications, the integrated framework of random-utility and product attribute updating presented here is capable of accommodating a variety of pharmaceutical marketing and development problems. This research demonstrates both the strengths of stated-preference market research and some of its shortcomings for pharmaceutical applications.
We examined whether distress responses of rats would be a negative reinforcer or not. In Experiment 1, two rats were placed in adjacent compartments. One rat was reinforced by a food pellet for pressing either of two levers. One of the levers produced food while the other produced food plus electric shock (0.5-2.0 mA) to the other rat. All rats preferred the former lever. In addition, this tendency was more prominent in rats that had experienced shock previously than those without experience. In Experiment 2, one lever produced food while the other produced food plus auditory stimuli, a recorded distress scream (65 dB) or a pure tone (3 kHz, 65 dB). Rats that chose between food and food plus another rat's scream avoided being exposed to the scream. Rats that chose between food and food plus the pure tone chose the two levers equally. These results suggest that negative emotional responses of the conspecifics could be a negative reinforcer.
The stochastic difference model assumes that decision makers trade normalized attribute value differences when making choices. The model is stochastic, with choice probabilities depending on the normalized difference variable, d, and a decision threshold, delta. The decision threshold indexes a person's sensitivity to attribute value differences and is a free estimated parameter of the model. Depending on the choice context, a person may be more or less sensitive to attribute value differences, and hence delta may be used to measure context effects. With proportional difference used as the normalization, the proportional difference model (PD) was tested with 9 data sets, including published data (e.g., J. L. Myers, M. M. Suydam, & B. Gambino, 1965; A. Tversky, 1969). The model accounted for individual and group data well and described violations of stochastic dominance, independence, and weak and strong stochastic transitivity.
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