Edmund Fantino

Choice, optimal foraging, and the delay-reduction hypothesis

Behaving organisms are continually choosing. Recently the theoretical and empirical study of decision making by behavioral ecologists and experimental psychologists have converged in the area of foraging, particularly food acquisition. This convergence has raised the interdisciplinary question of whether principles that have emerged from the study of decision making in the operant conditioning laboratory are consistent with decision making in naturally occurring foraging. One such principle, the “parameter-free delay-reduction hypothesis, ” developed in studies of choice in the operant conditioning laboratory, states that the effectiveness of a stimulus as a reinforcer may be predicted most accurately by calculating the decrease in time to food presentation correlated with the onset of the stimulus, relative to the length of time to food presentation measured from the onset of the preceding stimulus. Since foraging involves choice, the delay-reduction hypothesis may be extended to predict aspects of foraging. We discuss the strategy of assessing parameters of foraging with operant laboratory analogues to foraging. We then compare the predictions of the delay-reduction hypothesis with those of optimal foraging theory, developed by behavioral ecologists, showing that, with two exceptions, the two positions make comparable predictions. The delay-reduction hypothesis is also compared to several contemporary pscyhological accounts of choice. Results from several of our experiments with pigeons, designed as operant conditioning simulations of foraging, have shown the following: The more time subjects spend searching for or traveling between potential food sources, the less selective they become, that is, the more likely they are to accept the less preferred outcome; increasing time spent procuring (“handling”) food increases selectivity; how often the preferred outcome is available has a greater effect on choice then how often the less preferred outcome is available; subjects maximize reinforcement whether it is the rate, amount, or probability of reinforcement that is varied; there are no significant differences between subjects performing under different types of deprivation (open vs. closed economies). These results are all consistent with the delay-reduction hypothesis. Moreover, they suggest that the technology of the operant conditioning laboratory may have fruitful application in the study of foraging, and, in doing so, they underscore the importance of an interdisciplinary approach to behavior.

Observing reward-informative and -uninformative stimuli by normal children of different ages ☆

Abstract Normal children from ages 4 to 5, 9 to 10, and 13 to 14 years received points independent of responding according to a variable-time 30-sec schedule which alternated randomly with an extinction component. Money, for the older groups, or marbles, for the 4 to 5 year old children, were given to subjects following experimental sessions in exchange for points earned. Subjects were explicitly informed of the payoff and the schedule contingencies, including the fact that responding could not influence rate or distribution of points. Instead, presses on each of two levers (“observing responses”) produced stimuli. Stimuli positively correlated with points and stimuli uncorrelated with points were each chosen over stimuli correlated with extinction in every age group. These results are consistent with the conditioned-reinforcement hypothesis of observing but are inconsistent with the uncertainty-reduction hypothesis.

Behavior Analysis and Behavioral Ecology: A Synergistic Coupling

Recent trends in behavioral ecology and behavior analysis suggest that the two disciplines complement one another, underscoring the desirability of an integrated approach to behavior. Three examples from the foraging literature illustrate the potential value of an interdisciplinary approach. For example, a model of natural selection for foraging efficiency—optimal foraging theory—makes several predictions consistent with an hypothesis of a more proximate phenomenon, the reduction in delay to primary reinforcement. Not only are the ecological and behavior analytic approaches to behavior complementary, but each may provide insights into the operation of controlling variables in situations usually thought of as being the other’s domain.

Commodity specific rates of temporal discounting: Does metabolic function underlie differences in rates of discounting? ☆

Discounting rates vary as a function of commodity type. Previous studies suggest five potential characteristics of the commodity that could explain these differences: type of reinforcer (primary or secondary), if the commodity is perishable, if the commodity is satiable, if the commodity can be directly consumed, and immediacy of consumption. This paper suggests that these characteristics may best be viewed as related to a more fundamental characteristic: metabolic processing. In order to explore the possibility that metabolic processing underlies changes in discount rates, the difference in discounting between food, money, music CDs, DVDs, and books are compared. Music CDs, DVDs, and books share many characteristics in common with food, including gaining value through a physiological process, but are not directly metabolized. Results are consistent with previous findings of commodity specific discount rates and show that metabolic function plays a role in determining discount rates with those commodities that are metabolized being discounted at a higher rate. These results are interpreted as evidence that the discount rate for different commodities lies along a continuum with those that serve an exchange function rather than a direct function (money) anchoring the low end and those that serve a direct metabolic function capping the high end (food, alcohol, drugs).

The conjunction fallacy: A test of averaging hypotheses

The conjunction fallacy, in which individuals report that the conjunction of two events is more rather than less likely to occur than one of the events alone, is a robust phenomenon. We assessed the possibility that an analysis in terms of functional measurement methodology might be consistent with occurrence of the fallacy. A 3 × 3 design in which we varied the judged likelihood of the two components constituting the conjunction permitted us to assess the possibility that subjects judge the likelihood of conjunctions by averaging the likelihood of their component parts. The results were consistent with this possibility, and this interpretation was supported by analysis of the results in terms of functional measurement methodology.

What does and does not alleviate base-rate neglect under direct experience

A descriptive account was sought of when base-rate neglect does and does not occur under direct experience, and a theoretical model proposed of why it occurs, when it occurs. In two experiments, subjects experienced hundreds of trials in which they predicted which of two events would occur. One event occurred more often than the other, and subjects were aided by an imperfect cue. In Experiment 1, base-rate neglect occurred when cues were identical to outcomes but not whey they were arbitrarily related. Additionally, over 1600 trials, choice did not become stable at probability-matching, but tended toward optimality. In Experiment 2, the salience of irrelevant cues was found to have an effect, but to be incidental to base-rate neglect, and response bias effects were minimal. The results are consistent with the hypothesis that subjects have learned that base rates change more frequently than cue accuracies, and are therefore rationally underweighted. Copyright

Percentage reward in an operant analogue to foraging

Abstract Pigeons ( Columba livia ) responding on an operant, conditioning analogue to foraging could either accept or reject a variable-interval 20-s schedule which always led to food or a variable-interval 5-s schedule which led to food on only a percentage of trials. The probability of accepting the certain alternative increased as the percentage of food trials for the uncertain alternative decreased. The probability of accepting the uncertain alternative increased with the percentage of food trials for this alternative. Subjects receiving all of their food in the experiment (‘closed economy’) and those requiring supplementation (‘open economy’) preferred whichever alternative provided the higher overall mean rate of reinforcement.

Stimulus Change Contemporaneous with Food Presentation Maintains Responding in the Presence of Free Food

The presence or absence of a change in the ambient stimulus conditions upon entry into a food source controlled the frequency with which pigeons choose one of two concurrently available grain sources. Such changes characteristically accompany the production of response-produced food and account for prior reports of responding to produce food in the presence of freely available food.

Duration of components and response rates on multiple fixed-ratio schedules

Pigeons were exposed to a two-component multiple fixed-ratio X fixed-ratio Y schedule of reinforcement in which X was always less than Y. Components were equal in duration and alternated at rates that varied between 2 sec and 23.5 h. Relative response rate in the FR X component: (1) increased as the duration of components increased between 2 sec and 15 min, (2) was at a maximum between 15 min and 6 h, and (3) decreased as the duration of components increased from 6 h to 23.5 h. The changes in relative response rate were attributable primarily to changes in absolute response rates during the FR Y schedule as absolute response rates during the FR X schedule were relatively invariant. These results pose complexities for several theoretical formulations.

Context: a central concept.

Seminal research in several areas has underscored the central role played by context in the control of behavior. Landmark studies in classical conditioning (with both conditioned suppression and autoshaping procedures) and in conditioned reinforcement (using the observing paradigm) are reviewed. The role of context also proved central in the study of choice (including the matching law and delay-reduction theory). This latter work contributed to the development of experimental analogs to foraging behavior. Research on foraging has also highlighted the importance of context and has led to some counterintuitive predictions that are mediated by context.