Maintenance of Self-Imposed Delay of Gratification by Four Chimpanzees (Pan troglodytes) and an Orangutan (Pongo pygmaeus)

Abstract

Delay maintenance, which is the continuance over time of the choice to forgo an immediate, less preferred reward for a future, more preferred reward, was examined in 4 chimpanzees (Pan troglodytes) and 1 orangutan (Pongo pygmaeus). In the 1st experiment, the apes were presented with 20 chocolate pieces that were placed, one at a time, into a bowl that was within their reach. The apes could consume the available chocolate pieces at any time during a trial, but no additional pieces would be given. The total length of time taken to place the 20 items into the bowl ranged from 60 s to 180 s. All 5 apes delayed gratification on a majority of trials until all 20 chocolate pieces were presented. Unlike in most experiments with human children using this test situation, attention by the apes to the reward was not detrimental to delay maintenance. In a 2nd experiment with the chimpanzees only, 4 foods of differing incentive value were presented in different trials in the same manner as in Experiment 1. The chimpanzees were highly successful in obtaining all food pieces, and there was no difference in performance as a function of food type.

Goffin cockatoos wait for qualitative and quantitative gains but prefer ‘better’ to ‘more’

“…The value of the delayed reward can surpass the immediate one either in quality or quantity [7]. In the accumulated DGT, by contrast, the rewards mount up in quantity in the course of the delay and subjects can discontinue the accumulation through interference [8,14].…”

“…Indeed, rodents and most birds tested wait only few seconds for a delayed gain, and many monkeys wait less than a minute [2][3][4][5][6][7]. Some primates and dogs (possibly as an effect of domestication) do, however, accept delays over a minute and even show outstanding plasticity in decision-making relative to the benefits involved [8][9][10][11].…”

To Err Is (Not Only) Human: Fallibility as a Window Into Primate Cognition

“…Originally, chimpanzees and an orangutan showed that they could wait as food items accumulated, one at a time, within their reach, with the only rule being that more items accumulated as long as the apes did not eat any (Beran, 2002). Subsequent experiments involved fully computerized apparatus controlling the accumulation, to prevent any experimenter cuing (e.g., Beran & Evans, 2006).…”

Monkeys Wait to Begin a Computer Task when Waiting Makes Their Responses More Effective

“…Young et al"s (2011) escalating interest task consisted of multiple, relatively quick (10 seconds or less) inhibition trials as in the traditional operant delay discounting tasks often presented to laboratory animals (Ainslie, 1974;Logue, 1988). However, it also presented a "reward" value (i.e., damage potential) that increased across each trial, similar to how rewards sometimes accumulate in versions of the delay of gratification task presented to animals (Anderson, Kuroshima, & Fujita, 2010;Beran, 2002;Evans, 2007;Pele, Micheletta, Uhlrich, Thierry, & Dufour, 2011).…”

“…Participants became sensitive to this pattern and learned to overcome the initial inclination to fire any time an enemy was visible, and instead, maximized their performance by delaying their weapon usage and thereby allowing for near-maximum damage with each use. Young et al (2011) developed this test (at least in part) to have a method that was more comparable to the tests used most often to assess nonhuman animal (hereafter, animal) inhibitory control, namely, delay discounting and delay of gratification tasks (Beran, 2002;Dufour, Pelé, Sterck, & Thierry, 2007;Tobin, Chelonis, & Logue, 1993). Delay discounting tasks involve instantaneous choices between a lesser, more immediate, reward and a greater, more delayed, reward (Berns et al, 2007), whereas delay of gratification tasks involve waiting for as long as possible to take a reward that is present so that one can instead obtain a greater reward (Mischel et al, 1989).…”