When primatologist Liesbeth Sterck and her team at Utrecht University decided to offer long-tailed macaques more than one way to cooperate, the results upended a long-held assumption about animal social behavior. The researchers discovered that when just a single cooperation device was available, two adolescent males dominated nearly all interactions. But when the team introduced three — and then five — devices, cooperation spread evenly throughout the entire group, with even the previously dominant males beginning to work alongside different partners. The findings, published in the journal Animal Behaviour, suggest that decades of cooperation research may have captured only a narrow slice of how animals truly behave. The standard experimental setup — two animals pulling ropes together for a reward, with only one apparatus in the enclosure — has been the backbone of cooperation studies for years. It resembles a hunt for a single prey item, which does happen in nature. But Sterck points out that for monkeys foraging in trees and shrubs, such singular opportunities are the exception rather than the rule. "A fruit tree does not contain just one place where fruit is available, but many," she explains. "That allows animals to avoid one another, observe one another or actively seek each other out. But when there's only a single opportunity to obtain food, the social dynamics are very different." To illustrate the effect, Sterck uses a characteristically Dutch comparison: the Sinterklaas celebration, when small spiced biscuits called pepernoten are scattered across a wide area rather than offered at one spot. "That reduces competition and prevents arguments among children," she says. "We see something similar in our study." Biology student Jeroen Zewald, who conducted the research as part of his studies, frames the findings in terms of hunting. "Imagine hunting deer together when there is only a single animal available," he says. "You want a partner who is good at hunting but who will not keep the entire reward afterward. If there are prey animals everywhere, it matters much less whom you choose to cooperate with. The monkeys showed exactly this difference." Sterck is careful to note that previous studies using the single-device setup were not wrong — they simply revealed how animals behave in one specific circumstance. But the broader lesson, she argues, is that researchers should remain cautious about drawing sweeping conclusions from experiments that offer limited choices. The implications extend beyond cooperation: similar concerns could apply to studies of social learning and animal culture. For the macaques of Utrecht University, the takeaway is more immediate. When given multiple paths to the same reward, they found more ways to work together. The opportunity, it turns out, shapes the partnership.