Abstract
This study examined instantaneous and cumulative effects of competitive interactions on impulsiveness in the inter-temporal choices in domestic chicks. Chicks were trained to peck colored beads to gain delayed food rewards (1 or 6 grains of millet delivered after a delay ranging between 0 and 4.5 s), and were tested in binary choices between a small–short delay option (SS) and a large–long delay alternative (LL). To examine whether competitive foraging instantaneously changes impulsiveness, we intraindividually compared choices between two consecutive tests in different contexts, one with competitors and another without. We found that (1) the number of the choice of LL was not influenced by competition in the tests, but (2) the operant peck latency was shortened by competition, suggesting a socially enhanced incentive for food. To further examine the lasting changes, two groups of chicks were consecutively trained and tested daily for 2 weeks according to a “behavioral titration” procedure, one with competitors and another without. Inter-group comparisons of the choices revealed that (3) choice impulsiveness gradually decreased along development, while (4) the chicks trained in competition maintained a higher level of impulsiveness. These results suggest that competitive foraging causes impulsive choices not by direct/contextual modification. Causal link between the instantaneous enhancement of incentive and the gradual effects on impulsiveness remains to be examined. Some (yet unspecified) factors may be indirectly involved.
Highlights
Social interferences could shift behaviors that maximize the individual payoff
Peck latency was shorter in the competition block than in the no-competition block in both the long delay alternative (LL)/small–short delay option (SS) and the SS/S− trials (Figure 1C)
In model 2, which had the second smallest Akaike information criteria (AIC) (=95.76), the estimated coefficient of the trial types was positive, suggesting that the latency might be longer in the SS/S− trials than the LL/S− trials, somehow incompatible with the choice data (Figure 1B; see Discussion below)
Summary
When an animal is foraging in competition, a food item that is spatially/temporally remote should inevitably include a higher collection risk (McNamara and Houston, 1987; Benson and Stephens, 1996), and decision makers may reasonably redirect their choices toward a more proximate food item even though a large alternative is available. Such a rational forager could instantaneously change its impulsiveness as soon as a potential competitor appears; otherwise, it could change its choices much more slowly and gradually after accumulating the experiences of benefits and costs. It remained to be examined whether competitive foraging could cause instantaneous/contextual modification in choices and what (if any) of these modifications could underlie the observed cumulative effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
