Capuchin monkeys (Cebus apella) let lesser rewards pass them by to get better rewards

Bramlett, Jessica; Perdue, Bonnie M.; Evans, Theodore A.; Beran, Michael J.

doi:10.1007/s10071-012-0522-x

Cited by 57 publications

(83 citation statements)

References 29 publications

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“…discounting is also inconsistent with generally patient preferences observed in delay of gratification tasks in animals (26)(27)(28)(29). Thus, the present results are part of an emerging group of studies challenging the psychological reality of discounting as measured by intertemporal choice tasks.…”

Section: Discussioncontrasting

confidence: 42%

Postreward delays and systematic biases in measures of animal temporal discounting

Blanchard

Pearson

Hayden

2013

Proc. Natl. Acad. Sci. U.S.A.

132

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Intertemporal choice tasks, which pit smaller/sooner rewards against larger/later ones, are frequently used to study time preferences and, by extension, impulsivity and self-control. When used in animals, many trials are strung together in sequence and an adjusting buffer is added after the smaller/sooner option to hold the total duration of each trial constant. Choices of the smaller/sooner option are not reward maximizing and so are taken to indicate that the animal is discounting future rewards. However, if animals fail to correctly factor in the duration of the postreward buffers, putative discounting behavior may instead reflect constrained reward maximization. Here, we report three results consistent with this discounting-free hypothesis. We find that (i) monkeys are insensitive to the association between the duration of postreward delays and their choices; (ii) they are sensitive to the length of postreward delays, although they greatly underestimate them; and (iii) increasing the salience of the postreward delay biases monkeys toward the larger/later option, reducing measured discounting rates. These results are incompatible with standard discounting-based accounts but are compatible with an alternative heuristic model. Our data suggest that measured intertemporal preferences in animals may not reflect impulsivity, or even mental discounting of future options, and that standard human and animal intertemporal choice tasks measure unrelated mental processes.delay discounting | animal models | patience | foraging | rhesus macaque A nimal decision makers in natural environments regularly face choices between smaller rewards delivered sooner and larger rewards delivered later. To study how animals make this tradeoff, psychologists often measure preferences in intertemporal choice tasks, which directly pit smaller/sooner (SS) rewards against larger/later (LL) ones (1). Animals will typically sacrifice some of the long-term rate-maximizing benefits offered by the LL option to choose SS options. These present-biased preferences are sometimes thought to reflect impulsivity and poor self-control (2-4) and are often taken as a model for human impulsivity (2-6).In nearly all animal intertemporal choice studies, many trials are strung together in sequence. When faced with a choice between an SS and an LL option, rate-maximizing behavior may sometimes dictate choosing the SS option to begin the next trial more quickly and thus increase the overall rate of reward (7). To avoid this confound, animal psychologists normally add an adjusting buffer after the SS reward to equalize trial lengths. As a result, total time for either option is matched, and the ratemaximizing strategy is to always choose the LL option. However, this buffering strategy serves its purpose only if animals correctly incorporate postreward delays into their decisions and if they correctly associate specific postreward delays with the choices that produced them. If animals fail to do either of these things, then their preferences cannot be interpreted...

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Section: Discussioncontrasting

confidence: 42%

Postreward delays and systematic biases in measures of animal temporal discounting

Blanchard

Pearson

Hayden

2013

Proc. Natl. Acad. Sci. U.S.A.

132

View full text Add to dashboard Cite

show abstract

“…All monkeys had 24-hour access to water and were fed manufactured chow following test sessions, as well as various fruits and vegetables between 1600 and 1800 hours. Most monkeys had participated in at least one prior study of self-control behavior involving a manual or computerized test apparatus (Bramlett, Perdue, Evans, & Beran, 2012;Evans, 2007;Evans & Beran, 2007;Paglieri et al, 2013), but no monkey had participated in a behavioral inhibition task of this kind prior to this experiment.…”

Section: Methods Participantsmentioning

confidence: 99%

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

Evans¹,

Beran²

2014

AB&C

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-Rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella) performed a computerized inhibitory control task modeled after an "escalating interest task" from a recent human study (Young, Webb, & Jacobs, 2011). In the original study, which utilized a first-person shooter game, human participants learned to inhibit firing their simulated weapon long enough for the weapon"s damage potential to grow in effectiveness (up to 10 seconds in duration). In the present study, monkeys earned food pellets for eliminating arrays of target objects using a digital eraser. We assessed whether monkeys could suppress trial-initiating joystick movements long enough for the eraser to grow in size and speed, thereby making their eventual responses more effective. Monkeys of both species learned to inhibit moving the eraser for as long as 10 seconds, and they allowed the eraser to grow larger for successively larger target arrays. This study demonstrates an interesting parallel in behavioral inhibition between human and nonhuman participants and provides a method for future comparative testing of human and nonhuman test groups.

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“…Although capuchins have been repeatedly tested in several delay tolerance tasks (Addessi et al 2011(Addessi et al , 2014Amici et al 2008;Anderson et al 2010;Bramlett et al 2012;Evans et al 2012;Paglieri et al 2013b;Pelé et al 2011;Ramseyer et al 2006), no study has yet investigated whether they show a magnitude effect. This investigation is especially needed, since there is some evidence that the particular type of quantity pair presented in delay choice tasks may affect their temporal preferences.…”

Section: Introductionmentioning

confidence: 98%

When is it worth waiting for? Food quantity, but not food quality, affects delay tolerance in tufted capuchin monkeys

et al. 2015

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When faced with choices between smaller sooner options and larger later options (i.e. intertemporal choices), both humans and non-human animals discount future rewards. Apparently, only humans consistently show the magnitude effect, according to which larger options are discounted over time at a lower rate than smaller options. Most of the studies carried out in non-human animals led instead to negative results. Here, we tested ten tufted capuchin monkeys (Sapajus spp.) in a delay choice task to evaluate whether they show a magnitude effect when choosing between different quantities of the same food or when the options are represented by high- and low-preferred foods in different conditions. Whereas food quality did not play a role, we provided the first evidence of an effect of the reward amount on temporal preferences in a non-human primate species, a result with potential implications for the validity of comparative studies on the evolution of delay tolerance. In contrast with human results, but as shown in other animal species, capuchins' choice of the larger later option decreased as the amount of the smaller sooner option increased. Capuchins based their temporal preferences on the quantity of the smaller sooner option, rather than on that of the larger later option, probably because in the wild they virtually never have to choose between the above two options at the same time, but they more often encounter them consecutively. Thus, paying attention to the sooner option and deciding on the basis of its features may be an adaptive strategy rather than an irrational response.

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Capuchin monkeys (Cebus apella) let lesser rewards pass them by to get better rewards

Cited by 57 publications

References 29 publications

Postreward delays and systematic biases in measures of animal temporal discounting

Postreward delays and systematic biases in measures of animal temporal discounting

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

When is it worth waiting for? Food quantity, but not food quality, affects delay tolerance in tufted capuchin monkeys

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