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 she 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are Monkeys Aesthetists? Rensch (1957) Revisited.

Three experiments assessed whether capuchin monkeys (Cebus apella) and squirrel monkeys (Saimiri sciureus) prefer regular and symmetrical visual patterns. Pictorial representations of faces were included in 1 stimulus set. When the monkeys could pick up and manipulate small cards bearing the stimuli, all preferences expressed by capuchins and most of those expressed by squirrel monkeys were for regular stimuli. Symmetry of the patterns was influential but not essential. Some preferences were also found for faces. When images of the patterns were presented on a touch screen, capuchins continued to express preferences especially for regular and symmetrical stimuli, but they showed some avoidance of faces. Squirrel monkeys responded less discriminatingly to the touch screen stimuli. The findings provide support for B. Rensch's (1957) claim that monkeys prefer visual stimuli that humans find aesthetically pleasing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning and generalization of tool use by tufted capuchin monkeys (Cebus apella) in tasks involving three factors: Reward, tool, and hindrance.

We tested 4 captive tufted capuchin monkeys (Cebus apella) for their understanding of physical causality in variations of a 2-choice tool use task, 1 alternative of which allowed the monkeys easier access to food. Our monkeys, who had been adept at this task involving 2 items, that is, tool and food, quickly learned 3-term problems involving food, tool, and 1 type of hindrance (an obstacle or a trap, which could prevent success). All of the monkeys generalized their performance to new problems with the other type of hindrance and those with another familiar tool. These results suggest flexibility of their abilities to process complex physical information comprising 3 items in the environment, that is food–tool–hindrance spatial relationships. Such flexibility also implies that capuchin monkeys may possess rudimentary understanding of causal relationships involved in tool use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wavelength sensitivity of AATCC Blue wool lightfastness standards under light radiation

The fading characteristics of the AATCC Blue Wool L2 and L4 lightfastness standards were examined from the standpoint of wavelength sensitivity. Experiments were carried out by exposing a specimen to a narrow monochromatic band isolated from the dispersed polychromatic light emitted by a Xe lamp source. The wavelength sensitivity characteristics of Blue wool L2 and L4 lightfastness were determined on a radiant energy basis. Both Blue Wool Standards displayed peak maxima at 245 and 294 nm. The results indicated that UVA and UVB had a significant fading effect, whereas visible light caused fading to a small extent. Specific wavelengths caused Blue wool to significantly fade, suggesting that the total irradiated UV energy may not be an appropriate index. In addition, their spectral reflectances did not directly explain these characteristics of the standards.     

Cooperative problem solving by tufted capuchin monkeys (Cebus apella): Spontaneous division of labor, communication, and reciprocal altruism.

Using an experimentally induced cooperation task, the authors investigated whether tufted capuchin monkeys (Cebus apella) share the following 3 characteristics of cooperation with humans: division of labor, communication, and reciprocal altruism. In Experiment 1, the authors trained individual monkeys to perform the necessary sequence of actions for rewards and tested them in pairs to assess whether they could solve the task by spontaneously dividing the sequence of actions. All pairs solved this task. In Experiment 2, monkeys worked in the cooperation task and a task requiring no partner help. They looked at the partner significantly longer in the former task than in the latter, but communicative intent could not be determined. In Experiment 3, only 1 of 2 participants obtained a reward on each trial. Monkeys maintained cooperation when their roles were reversed on alternate trials. Their cooperative performances demonstrated division of labor; results suggest task-related communication and reciprocal altruism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay of gratification in capuchin monkeys (cebus apella) and squirrel monkeys (saimiri sciureus).

In two separate series of experiments four capuchin monkeys (Cebus apella) and four squirrel monkeys (Saimiri sciureus) were given demonstration trials in which a human transferred six pieces of food, one by one, from out of each monkey's reach to within reach. On test trials the monkey could reach for the transferred food at any time, an action that ended the trial. Therefore, it was in the monkey's interest to allow food items to accumulate before reaching for food. No capuchin monkey showed delay of gratification in the first phase of testing. An attempt to facilitate performance by presenting a single free food item immediately before the transfer failed (Phase 2). In Phase 3, when the transferred food items increased progressively in size, two capuchins maintained delays, and frequently waited for all 6 items to accumulate. One squirrel monkey started to delay gratification in Phase 1, and another did so in Phase 3. A return to single-sized food items did not impair the monkeys' ability to delay. Short (1 s) interitem delays were generally easier to maintain than longer delays (3 or 5 s). In both species the delaying individuals bridged the delays idiosyncratically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention to combined attention in New World monkeys (Cebus apella, Saimiri sciureus).

Co-orientation by capuchin (Cebus apella) and squirrel (Saimiri sciureus) monkeys in response to familiar humans abruptly switching the direction of their visual attention was recorded. Co-orientation occurred more frequently overall in capuchins than squirrel monkeys. Capuchins showed a tendency to habituate within trials involving consecutive attention switches performed by 2 different people, whereas squirrel monkeys co-oriented more when the 2nd attention switch was by a 2nd actor. These results suggest variable attention-processing abilities in New World monkeys, including differences in summation of attention by others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Training squirrel monkeys (Saimiri sciureus) to deceive: Acquisition and analysis of behavior toward cooperative and competitive trainers.

Three squirrel monkeys (Saimiri sciureus) learned to reach toward a container that covered food if a cooperative trainer rewarded such reaches by giving the food. A competitive trainer kept any food found, but wrong selections by this trainer were also rewarded. The monkeys initially reached toward the baited container indiscriminately, but gradually and with the aid of color-cued containers, all 3 reliably reached "honestly" and "deceptively" in the presence of the cooperative and competitive trainers, respectively. The monkeys did not appear to take the trainers' knowledge about the location of the food into account, and deception did not occur if food was placed under the normally unbaited container. With additional containers present, monkeys misled the competitive trainer into selecting the unbaited container farthest from the baited one. Although not indicative of mental attribution, the monkeys' behavior suggests awareness of the acquired communicative function of the reaching response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)