Does own experience affect perception of others’ actions in capuchin monkeys (Cebus apella)?

Anticipating another’s actions is an important ability in social animals. Recent research suggests that in human adults and infants one’s own action experience facilitates understanding and anticipation of others’ actions. We investigated the link between first-person experience and perception of another’s action in adult tufted capuchin monkeys (Sapajus apella spp., formerly Cebus apella spp.). In Experiment 1, the monkeys observed a familiar human (actor) trying to open a container using either a familiar or an unfamiliar action. They looked for longer when the actor tried to open the container using a familiar action. In Experiment 2, the actor performed two novel actions on a new container. The monkeys looked equally at the two actions. In Experiment 3, the monkeys were trained to open the container using one of the novel actions in Experiment 2. After training, we repeated the same procedure as in Experiment 2. The monkeys looked for longer when the actor manipulated the container using the action they had practiced than when she used the unfamiliar action. These results show that knowledge derived from one’s own experience impacts perception of another’s action in these New World monkeys.     

Do tufted capuchin monkeys (Cebus apella) spontaneously deceive opponents? A preliminary analysis of an experimental food-competition contest between monkeys

A new laboratory procedure which allows the study of deceptive behavior in nonhuman primates is described. Pairs of tufted capuchin monkeys faced each other in a food-competition contest. Two feeder boxes were placed between the monkeys. A piece of food was placed in one of the boxes. The subordinate individual was able to see the food and to open the box to obtain the bait. A dominant male was unable to see the food or to open the box but was able to take the food once the box was opened by the subordinate. In experiment 1, two of four subordinate monkeys spontaneously started to open the unbaited box first with increasing frequency. Experiment 2 confirmed that this "deceptive" act was not due to a drop in the rate of reinforcement caused by the usurping dominant male, under the situation in which food sometimes automatically dropped from the opened box. In experiment 3, two subordinate monkeys were rerun in the same situation as experiment 1. One of them showed some recovery of the "deceptive" act but the other did not; instead the latter tended to position himself on the side where there was no food before he started to open the box. Although the results do not clearly indicate spontaneous deception, we suggest that operationally defined spontaneous deceptive behaviors in monkeys can be analyzed with experimental procedures such as those used here. Accepted after revision: 13 June 2001 Electronic Publication     

How do tufted capuchin monkeys (Cebus apella) understand causality involved in tool use?

Four tufted capuchin monkeys (Cebus apella) were trained to choose from 2 hook-like tools, 1 of which successfully led to collecting food, whereas the other did not because of inappropriate spatial arrangement of the tool and the food. In Experiment 1, all of the monkeys successfully learned the basic task. The monkeys performed successfully with tools of novel colors and shapes in Experiments 2-5. These results demonstrate that the monkeys used the spatial arrangement of the tool and the food as a cue. However, they failed when there were obstacles (Experiment 6) or traps (Experiment 7) on the path along which the monkeys dragged tools. These results may suggest that capuchin monkeys understand the spatial relationship between 2 items, namely, food and the tool, but do not understand the spatial relationship among 3 items, namely, food, tool, and the environmental condition. The possible role of stimulus generalization is also considered.     

Do squirrel monkeys (<Emphasis Type="Italic">Saimiri sciureus</Emphasis>) and capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>) predict that looking leads to touching?

Squirrel monkeys (Saimiri sciureus) and capuchin monkeys (Cebus apella) were tested using an expectancy violation procedure to assess whether they use an actors gaze direction, signaled by congruent head and eye orientation, to predict subsequent behavior. The monkeys visually habituated to a repeated sequence in which the actor (a familiar human or a puppet) looked at an object and then picked it up, but they did not react strongly when the actor looked at an object but then picked up another object. Capuchin monkeys responses in the puppet condition were slightly more suggestive of expectancy. There was no differential responding to congruent versus incongruent look–touch sequences when familiarization trials were omitted. The weak findings contrast with a strongly positive result previously reported for tamarin monkeys. Additional evidence is required before concluding that behavior prediction based on gaze cues typifies primates; other approaches for studying how they process attention cues are indicated.This revised version was published online in March 2004 with corrections to Fig. 2. The number 1 in the bottom left panel should be a cross and was, moreover, misaligned.     

Observational learning in capuchin monkeys: a video deficit effect

Young human children have been shown to learn less effectively from video or televised images than from real-life demonstrations. Although nonhuman primates respond to and can learn from video images, there is a lack of direct comparisons of task acquisition from video and live demonstrations. To address this gap in knowledge, we presented capuchin monkeys with video clips of a human demonstrator explicitly hiding food under one of two containers. The clips were presented at normal, faster than normal, or slower than normal speed, and then the monkeys were allowed to choose between the real containers. Even after 55 sessions and hundreds of video demonstration trials the monkeys’ performances indicated no mastery of the task, and there was no effect of video speed. When given live demonstrations of the hiding act, the monkeys’ performances were vastly improved. Upon subsequent return to video demonstrations, performances declined to pre-live-demonstration levels, but this time with evidence for an advantage of fast video demonstrations. Demonstration action speed may be one aspect of images that influence nonhuman primates’ ability to learn from video images, an ability that in monkeys, as in young children, appears limited compared to learning from live models.     

Capuchin monkeys (Cebus apella) are sensitive to others’ reward: an experimental analysis of food-choice for conspecifics

The issue whether non-human primates have other-regarding preference and/or inequity aversion has been under debate. We investigated whether tufted capuchin monkeys are sensitive to others’ reward in various experimental food sharing settings. Two monkeys faced each other. The operator monkey chose one of two food containers placed between the participants, each containing a food item for him/herself and another for the recipient. The recipient passively received either high- or low-value food depending on the operator’s choice, whereas the operator obtained the same food regardless of his/her choice. The recipients were either the highest- or lowest-ranking member of the group, and the operators were middle-ranking. In Experiment 1, the operators chose the high-value food for the subordinate recipient more frequently than when there was no recipient, whereas they were indifferent in their choice for the dominant. This differentiated behavior could have been because the dominant recipient frequently ate the low-value food. In Experiment 2, we increased the difference in the value of the two food items so that both recipients would reject the low-value food. The results were the same as in Experiment 1. In Experiment 3, we placed an opaque screen in front of the recipient to examine effects of visual contact between the participants. The operators’ food choice generally shifted toward providing the low-value food for the recipient. These results suggest that capuchins are clearly sensitive to others’ reward and that they show other-regarding preference or a form of inequity aversion depending upon the recipients and the presence of visual contact.