Social influences of competition on impulsive choices in domestic chicks

Abstract

Social factors involved in the control of impulsiveness were examined in domestic chicks. In binary choices between a large/long-delay option (LL) and a small/short-delay alternative (SS), chicks that had been competitively trained in groups of three individuals showed fewer choices of LL than did those trained in isolation (experiment 1), suggesting that competition causes impulsive choice. In experiment 2, in order to identify the critical factor involved, we tested the effects of perceived competition (coincident feeding without interruption) and scrounging (gaining food without pecking bead) separately. To examine the effects of risk/noise that individual chicks experienced in competition, the food amount varied randomly in trials according to a binomial distribution around the expected mean. Perceived competition primarily contributed to the influence on the impulsive choice, whereas the contribution of scrounging was weaker. Collection risk did not explain the social influences since the perceived competition was not accompanied by actual interruption of the delayed food reward. The risk owing to variable food per se did not cause impulsive choices. Coincident foraging during competition is thought to play a critical role.

Competitor suppresses neuronal representation of food reward in the nucleus accumbens/medial striatum of domestic chicks

“…Second, occurrence of suppression in both SS and LL trials (Fig. 5D, 6 and 7) is also counter-intuitive as an account for the development of impulsive choices biased for the SS option [29,33]. Here we theorize that a competitively foraging chick can distract the subject from attending to the LED cues, and that the cue-period activity represents attention to cues.…”

“…Note that a brief mechanical lag (Δ = 0.2-0.3 s) inevitably occurred before the food was supplied. Based on our previous studies [29,33], the delay for LL (or SS) was fixed at 1.5 + Δ s (or Δ s) in all chicks studied, so that chicks could have chosen LL and SS options equally if tested in binary choices. It is to be noticed that we did not routinely examine chicks in binary choice tests and did not adjust the LL delay accordingly.…”

“…caused an identical impulsive shift [29,33]. It is to be stressed that subject chicks did not instantaneously change the choice impulsiveness in the context of 5 pseudo-competition, though operant peck latency was shortened as an acute effect [33].…”

“…This theoretical prediction has proven valid in domestic chicks. When compared with those trained in isolation, chicks trained in competition gradually develop enhanced impulsiveness when forced to choose between a small amount of food following a short delay and a large amount of food following a long delay [29].…”

Behavioural and pharmacological effects of fluvoxamine on decision-making in food patches and the inter-temporal choices of domestic chicks

“…A thermo-controlled box (21 × 19 × 25 cm, kept at ca. 27-30°C and illuminated by light bulbs) was used [24][25][26]. One of the surrounding walls was equipped with a pair of holes placed side by side (separated by 3 cm, 4 cm above floor level), through which one or two colored beads (white, blue or red) were presented for 1 sec.…”