When it comes to delaying gratification for greater reward, parrots compare well with chimpanzees and out-perform capuchin monkeys, a new study reveals.
Delayed gratification experiments were famously performed on children in the 1980s by Walter Mischel – the “marshmallow tests”. Will a child take one marshmallow now, or wait and have two marshmallows as a reward for delaying the joy of eating that one marshmallow straight away?
Researchers in cognitive science call this economic decision-making. The process is cognitively challenging, because it involves a complex and thorough assessment of the current situation, together with an understanding of future reward as a result of controlling one’s impulses.
Previous animal studies have used actual items of food, ranging from from the highly coveted items such as pecans to less desirable offerings such as a piece of dry biscuit. But at the Max Planck Institute of Ornithology in Germany, researchers Auguste von Bayern and Anastasia Krasheninnikova felt that such studies created ambiguous results. Non-primate animals that lack functional hands must hold the food in their mouths or bills before making a decision, making the urge to simply eat it harder to resist.
The use of symbolic tokens instead of actual food rewards to test economic decision-making overcomes this issue, and has been used previously with chimps (Pan troglodytes) and capuchin monkeys (Cebus apella). This research, published in the journal Nature, is the first to use the token method with parrots.
To conduct the study, von Bayern and the team trained 36 individuals from four parrot species to associate particular tokens with specific food items: a piece of plastic pipe for a high value piece of walnut, a metal bracket for a medium value sunflower seed, and a metal loop for a single dry corn kernel.
Goffins cockatoos (Cacatua goffini) have previously demonstrated exceptional cognitive abilities, and choose easily between an item of food or a tool that will enable access to a greater reward. This new study looks at the Psittacoidea family of parrots, distantly related to the cockatoos, and represented by specialist fruit foragers, the great green macaw (Ara ambiguuus) and blue-throated macaw (Ara glaucogularis), as well as generalist foragers, the blue-headed macaw (Primolius couloni) and African grey parrot (Psittacus erithacus).
When provided with a choice between a food item and a token that could be exchanged for more preferred food, all four species inhibited their impulsive reactions and selected the token significantly more often than chance, thus maximising their pay-off. These results are comparable to those seen in testing with chimpanzees, and surpassed the results of testing with capuchin monkeys.
As predicted by the researchers, the specialist feeders performed best in the testing. In fact, one great green macaw, an obviously spirited individual named Shouty, excelled in all tests.
During testing, some individuals, mostly African greys, showed a strong preference for the token itself as an object of play, even when highly valued walnut pieces were offer.
African greys and other parrots such as cockatoos are known to engage in object play – and this study suggests that such behaviour needs to be kept in mind when using token exchange as a method for studying parrots.
Parrots using tokens and trading for treats in a controlled laboratory situation tell us a lot about their cognitive abilities, but how does this translate to their lives in the wild?
“Given that wild parrots are so difficult to track, to date we know little about the ecological challenges most parrots encounter in their habitats in the wild, such as deciding where to go and how long to stay in a given feeding site,” says von Bayern.
“However, in our experimental setting we have found that they are capable of making surprisingly subtle decisions to maximise their payoff while minimising their effort. This is a fascinating indication that such decisions may matter greatly in their natural environment.”
Tanya Loos is an ecologist and science writer based in regional Victoria, Australia.
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