{"id":481284,"date":"2026-10-01T06:04:16","date_gmt":"2026-10-01T06:04:16","guid":{"rendered":"https:\/\/www.newsbeep.com\/us-ca\/481284\/"},"modified":"2026-10-01T06:04:16","modified_gmt":"2026-10-01T06:04:16","slug":"chimps-plunder-less-pineapple-from-friends-and-expect-them-to-do-the-same","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/us-ca\/481284\/","title":{"rendered":"Chimps plunder less pineapple from friends \u2014 and expect them to do the same"},"content":{"rendered":"

In recent years, scientists have shown<\/a> that chimpanzees favor certain peers by picking whom they prefer to groom and selectively sharing food. The behavior offers a glimpse into humanity\u2019s prosocial evolutionary past.\u00a0<\/p>\n

But a question has lingered: How might a chimpanzee friendship affect antisocial acts?<\/p>\n

In a new study that uses fruit as the loot, UC Berkeley researchers found that chimps steal less from their friends, and that friendship status affected the emotional expression of both victim and thieves. Closely bonded chimps swiped pineapple pieces from one another less frequently than those with weaker relationships. Additionally, victims were quicker to calm down when the thief was a friend, and thieves showed less hostility when stealing from a bonded pal than from a non-friend.<\/p>\n

\"OdedOded Ritov<\/p>\n

The new research deepens our understanding of the emotional underpinnings of our social lives, said Oded Ritov<\/a>, the paper\u2019s first author and a Berkeley psychology Ph.D. student.<\/p>\n

\u201cCollaborative relationships are important for our well-being, health and survival,\u201d said Ritov, who works with Berkeley\u2019s Social Origins Lab<\/a>. \u201cIncreasingly, we\u2019re understanding that this isn\u2019t something that\u2019s unique to us, but that other animals have friends as well.\u201d<\/p>\n

The paper was published online this month<\/a> and will appear in the November issue of the journal Evolution and Human Behavior.\u00a0<\/p>\n

Scientists are sometimes hesitant to describe an apparently close relationship between chimps as akin to human friendship, arguing that we can\u2019t grasp their cognitive and emotional complexity. To identify those who showed signs of a close relationship, researchers observed 26 chimps for more than 800 hours at the Ngamba Island Chimpanzee Sanctuary in Uganda. The team documented which chimps appeared to be closely bonded \u2014\u00a0like friends \u2014 by taking note of their grooming patterns, daily interactions and how regularly they were within arm\u2019s reach of others.\u00a0<\/p>\n

Then they set up two rooms. One contained a \u201cvictim\u201d chimp with three trays baited with pineapple. Researchers attached a rope to the trays and led it into the other room, where a second chimp \u2014 the thief \u2014\u00a0could either leave the rope alone or yank it to steal the pineapple.\u00a0<\/p>\n

Chimps stole in 70% of trials with non-friends, compared with 61% of trials with friends. While 9 percentage points may not seem large, each chimp experienced both friend and non-friend conditions, a methodological technique that leads to a higher degree of confidence that the difference is meaningful and not just random chance.<\/p>\n

\u201cOurs is the first study to show that they\u2019re able to hold back antisocial behavior with their friends,\u201d Ritov said.<\/p>\n

Researchers also measured how the victims responded to being stolen from by evaluating their stomping, fist-pounding and screeching. Victims were initially angrier when friends stole from them but quickly moderated their feelings compared with when non-friends stole from them.\u00a0<\/p>\n

The thieves\u2019 behavior also changed. When non-friends were the thieves, the thieves expressed negative emotions for much longer, suggesting they viewed the interaction as more hostile.\u00a0<\/p>\n

\u201cThis suggests that there may be mutual expectations in chimps from both sides of the friendship, which makes it seem more like the complex friendships we see in humans,\u201d Ritov said.<\/p>\n

Jan Engelmann<\/a>, an associate professor of psychology and principal investigator with the Social Origins Lab, said previous work has shown relationship-specific intentions in nonhuman primates. But human friendships are about more than special intentions, he added \u2014 they\u2019re about stronger expectations.\u00a0<\/p>\n

\u201cWe expect more of our friends,\u201d said Engelmann, a senior author of the paper. \u201cThese findings really deepen our understanding of the evolutionary roots of friendships. This is, to my knowledge, the first evidence showing that also chimpanzees expect and maybe demand special treatment from their friends. These kinds of social expectations might form the basis of human moral principles.\u201d<\/p>\n

The paper adds to Ritov\u2019s work that focuses on the evolution of human behavior and how morals and norms are part of our core being, traceable to other animals. He has recently studied whether nonhuman animals have a sense of fairness<\/a> and is broadly interested in how emotions unfold across cultures and species.\u00a0\u00a0<\/p>\n

\u201cWe think that these expectations might be the basic building blocks of the larger-scale cooperation we see in humans,\u201d Ritov said. \u201cThe expectations that chimpanzees have from their friends or close collaborative partners might have scaled up to more generalized expectations for how we should treat each other.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"In recent years, scientists have shown that chimpanzees favor certain peers by picking whom they prefer to groom…\n","protected":false},"author":2,"featured_media":481285,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[34],"tags":[143,145,144,45139,6080],"class_list":["post-481284","post","type-post","status-publish","format-standard","has-post-thumbnail","category-oakland","tag-oakland","tag-oakland-headlines","tag-oakland-news","tag-psychology","tag-research"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts\/481284","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/comments?post=481284"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/posts\/481284\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/media\/481285"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/media?parent=481284"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/categories?post=481284"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us-ca\/wp-json\/wp\/v2\/tags?post=481284"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}