Exploration and learning in capuchin monkeys (Sapajus spp.): the role of action–outcome contingencies

Animals have a strong propensity to explore the environment. Spontaneous exploration has a great biological significance since it allows animals to discover and learn the relation between specific behaviours and their consequences. The role of the contingency between action and outcome for learning has been mainly investigated in instrumental learning settings and much less in free exploration contexts. We tested 16 capuchin monkeys (Sapajus spp.) with a mechatronic platform that allowed complex modules to be manipulated and to produce different outcomes. Experimental subjects could manipulate the modules and discover the contingencies between their own specific actions and the outcomes produced (i.e., the opening and lighting of a box). By contrast, Control subjects could operate on the modules, but the outcomes experienced were those performed by their paired Experimental subjects (“yoked-control” paradigm). In the exploration phase, in which no food reward was present, Experimental subjects spent more time on the board and manipulated the modules more than Yoked subjects. Experimental subjects outperformed Yoked subjects in the following test phase, where success required recalling the effective action so to open the box, now baited with food. These findings demonstrate that the opportunity to experience action–outcome contingencies in the absence of extrinsic rewards promotes capuchins’ exploration and facilitates learning processes. Thus, this intrinsically motivated learning represents a powerful mechanism allowing the acquisition of skills and cognitive competence that the individual can later exploit for adaptive purposes.     

What limits tool use in nonhuman primates? Insights from tufted capuchin monkeys (Sapajus spp.) and chimpanzees (Pan troglodytes) aligning three-dimensional objects to a surface

Perceptuomotor functions that support using hand tools can be examined in other manipulation tasks, such as alignment of objects to surfaces. We examined tufted capuchin monkeys’ and chimpanzees’ performance at aligning objects to surfaces while managing one or two spatial relations to do so. We presented six subjects of each species with a single stick to place into a groove, two sticks of equal length to place into two grooves, or two sticks joined as a T to place into a T-shaped groove. Tufted capuchins and chimpanzees performed equivalently on these tasks, aligning the straight stick to within 22.5° of parallel to the groove in approximately half of their attempts to place it, and taking more attempts to place the T stick than two straight sticks. The findings provide strong evidence that tufted capuchins and chimpanzees do not reliably align even one prominent axial feature of an object to a surface, and that managing two concurrent allocentric spatial relations in an alignment problem is significantly more challenging to them than managing two sequential relations. In contrast, humans from 2 years of age display very different perceptuomotor abilities in a similar task: they align sticks to a groove reliably on each attempt, and they readily manage two allocentric spatial relations concurrently. Limitations in aligning objects and in managing two or more relations at a time significantly constrain how nonhuman primates can use hand tools.     

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 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     

Do capuchin monkeys use weight to select hammer tools?

The extent to which tool-using animals take into account the properties of the tool is little explored. The use of percussors to crack open encapsulated fruit is a complex form of tool use, the choice of an adequate tool being a critical aspect in success. Several properties (e.g., material, resistance, friability, shape and weight) affect the suitability of an object to open a hard-shelled nut, with weight being amongst the most important factors. In general, heavier tools require fewer strikes to crack open a nut.     

Do monkeys think in metaphors? Representations of space and time in monkeys and humans

Research on the relationship between the representation of space and time has produced two contrasting proposals. ATOM posits that space and time are represented via a common magnitude system, suggesting a symmetrical relationship between space and time. According to metaphor theory, however, representations of time depend on representations of space asymmetrically. Previous findings in humans have supported metaphor theory. Here, we investigate the relationship between time and space in a nonverbal species, by testing whether non-human primates show space–time interactions consistent with metaphor theory or with ATOM. We tested two rhesus monkeys and 16 adult humans in a nonverbal task that assessed the influence of an irrelevant dimension (time or space) on a relevant dimension (space or time). In humans, spatial extent had a large effect on time judgments whereas time had a small effect on spatial judgments. In monkeys, both spatial and temporal manipulations showed large bi-directional effects on judgments. In contrast to humans, spatial manipulations in monkeys did not produce a larger effect on temporal judgments than the reverse. Thus, consistent with previous findings, human adults showed asymmetrical space–time interactions that were predicted by metaphor theory. In contrast, monkeys showed patterns that were more consistent with ATOM.     

Do advertised preferences predict the behavior of speed daters?

Because researchers are making increasing use of data gleaned from Internet dating sites, it is important to know if the preferences people specify in Internet advertisements predict the choices that they actually make. HurryDate, a commercial speed‐dating firm, collected data from over 10,000 people in their 20s, 30s, and 40s who participated in speed‐dating events in cities across the United States. The present analysis compared these speed daters’ advertised preferences with their decisions to attend particular events and their choices of potential partners at the events they attended. Findings indicated that speed daters’ advertisements reflect frequently replicated sex differences and assortative patterns and that these advertised mate preferences predicted their decisions to attend particular events. Advertised preferences did not, in contrast, substantially predict decisions within events. These results support the conclusion that advertised preferences predict behavior in the mating domain in some contexts but not others.     

Do emotions play an essential role in moral judgments?

The past few decades of moral psychology research have yielded empirical anomalies for rationalist theories of moral judgments. An increasing number of psychologists and philosophers argue that these anomalies are explained well by sentimentalism, the thesis that the presence of an emotion is necessary for the formation of a sincere moral judgment. The present review reveals that while emotions and moral judgments indeed often co-occur, there is scant evidence that emotions directly cause or constitute moral judgments. Research on disgust, anger, sympathy, and guilt indicates that people only reliably experience emotions when judging conduct that is relevant to the welfare of the self and valued others. Moreover, many recent studies have either failed to replicate or exposed crucial confounds in the most cited evidence in support of sentimentalism. Moral psychologists should jettison sentimentalism, and focus instead on how considerations of harm and welfare—the core concepts of rationalist theories— interact with empirical beliefs to shape moral judgments.     

Do Carolina chickadees (Poecile carolinensis) and tufted titmice (Baeolophus bicolor) use predator eyes in risk assessment?

Animal Cognition - Previous studies have found that Carolina chickadees and tufted titmice use a predator’s head orientation to determine risk, taking fewer seeds from a feeder if an avian...     

Is the inversion effect in rhesus monkeys face-specific?

This study investigated the face inversion effect in rhesus monkeys (Macaca mulatta). Face stimuli consisted of ten black-and-white examples of unfamiliar rhesus monkey faces, brown capuchin faces, and human faces. Two non-face categories included ten examples of automobiles and abstract shapes. All stimuli were presented in a sequential matching-to-sample format using an automated joystick-testing paradigm. Subjects performed significantly better on upright than on inverted presentations of automobiles, rhesus monkey and capuchin faces, but not human faces or abstract shapes. These results are inconsistent with data from humans and chimpanzees that show the inversion effect only for categories of stimuli for which subjects have developed expertise. The inversion effect in rhesus monkeys does not appear to be face-specific, and should therefore not be used as a marker of specialized face processing in this species. Received: 18 November 1998 / Accepted after revision: 9 May 1999     

Do infants show social preferences for people differing in race?

Do infants develop meaningful social preferences among novel individuals based on their social group membership? If so, do these social preferences depend on familiarity on any dimension, or on a more specific focus on particular kinds of categorical information? The present experiments use methods that have previously demonstrated infants’ social preferences based on language and accent, and test for infants’ and young children’s social preferences based on race. In Experiment 1, 10-month-old infants took toys equally from own- and other-race individuals. In Experiment 2, 2.5-year-old children gave toys equally to own- and other-race individuals. When shown the same stimuli in Experiment 3, 5-year-old children, in contrast, expressed explicit social preferences for own-race individuals. Social preferences based on race therefore emerge between 2.5 and 5 years of age and do not affect social choices in infancy. These data will be discussed in relation to prior research finding that infants’ social preferences do, however, rely on language: a useful predictor of group or coalition membership in both modern times and humans’ evolutionary past.     

What perceptual rules do capuchin monkeys (Cebus apella) follow in completing partly occluded figures?

Capuchin monkeys (Cebus apella) matched a variety of rodlike figures, distinguishable only by their central portions. The monkeys were then tested for perceptual completion rules by examining which comparison figures they would choose as matching the sample with the critical central portion occluded by a horizontal belt. In Experiment 1, the monkeys overwhelmingly chose a straight rod over disconnected rods and rods having irregular shapes at their center, irrespective of the presence-absence of common motion of visible parts of the samples. The monkeys chose a connected rod for relatable rods and disconnected rods for non-relatable ones in Experiment 2. In Experiments 3 and 4, some of the monkeys chose rods specified by the global regularity of the contour, whereas others did not. Experiment 5 showed that humans and capuchin monkeys basically follow similar perceptual rules in completing occluded contours, but the global regularity rule may be stronger in humans.     

Do big-brained animals play more? Comparative analyses of play and relative brain size in mammals

It has been hypothesized that play is more likely to be present in larger brained species. We tested this hypothesis in mammals using independent contrasts, a method that controls for phylogenetic relatedness. Comparisons across 15 orders revealed that the prevalence and complexity of play was significantly correlated with brain size, with larger brained orders having more playful species. Three orders, Rodentia, Marsupialia, and Primates, were used for within-order comparisons among species and, where possible, among families. The comparisons were not significant for rodents or primates, and those for marsupials yielded inconsistent results. Therefore, although a strong relationship is present at the highest taxonomic level of comparison, it diminishes or evaporates at lower level comparisons.     

Do rhesus monkeys (Macaca mulatta) perceive the Zöllner illusion?

A long-standing debate surrounds the issue of whether human and nonhuman animals share the same perceptual mechanisms. In humans, the Zöllner illusion occurs when two parallel lines appear to be convergent when oblique crosshatching lines are superimposed. Although one baboon study suggests that they too might perceive this illusion, the results of that study were unclear, whereas two recent studies suggest that birds see this illusion in the opposite direction from humans. It is currently unclear whether these mixed results are an artifact of the experimental design or reflect a peculiarity of birds’ visual system or, instead, a wider phenomenon shared among nonhuman mammals. Here, we trained 6 monkeys to select the narrower of two gaps at the end of two convergent lines. Three different conditions were set up: control (no crosshatches), perpendicular (crosshatches not inducing the illusion), and Zöllner (crosshatches inducing the illusion in humans). During training, the degrees of convergence between the two lines ranged from 15° to 12°. Monkeys that reached the training criterion were tested with more difficult discriminations (11°–1°), including probe trials with parallel lines (0°). The results showed that monkeys perceived the Zöllner illusion in the same direction as humans. Comparison of these data with the data from bird studies points toward the existence of different orientation-tuned mechanisms between primate and nonprimate species.     

Nonverbal working memory of humans and monkeys: Rehearsal in the sketchpad?

Investigations of working memory tend to focus on the retention of verbal information. The present experiments were designed to characterize the active maintenance rehearsal process used in the retention of visuospatial information. Rhesus monkeys (Macaca mulatta;N=6) were tested as well as humans (totalN=90) because these nonhuman primates have excellent visual working memory but, unlike humans, cannot verbally recode the stimuli to employ verbal rehearsal mechanisms. A series of experiments was conducted using a distractor-task paradigm, a directed forgetting procedure, and a dual-task paradigm. No evidence was found for an active maintenance process for either species. Rather, it appears that information is maintained in the visuospatial sketchpad without active rehearsal.     

Do aggressive people play violent computer games in a more aggressive way? Individual difference and idiosyncratic game-playing experience.

ABSTRACT This study investigates whether individual difference influences idiosyncratic experience of game playing. In particular, we examine the relationship between the game player's physical-aggressive personality and the aggressiveness of the player's game playing in violence-oriented video games. Screen video stream of 40 individual participants' game playing was captured and content analyzed. Participants' physical aggression was measured before the game play. The results suggest that people with more physical-aggressive personality engage in a more aggressive style of playing, after controlling the differences of gender and previous gaming experience. Implications of these findings and direction for future studies are discussed.     

Do Children Have Privacy Rights in the Classroom?

Arguing that everyone has a right to privacy as control overaccess to `intimate' aspects of one's life, this author draws on thework of Julie Inness to discuss children's rights to privacy inclassrooms. Even if it is agreed that pupils should exercise this right,a central point is that there may be moral or other value considerationsthat justify setting the right aside. Among selected complexities, animportant extension is the right to psychological processes throughwhich learners acquire new knowledge.     

Do ad metaphors enhance or dilute the consumers' brand preferences? Exploring the moderating role of goal orientation

This research aims to explore the impacts of ad metaphors and goal orientation on the relationship between brand commitment and attitudes toward the competitor brands. Results show that prevention‐focused consumers with high brand commitment do not exhibit differentially favorable attitudes toward the competitor brands, regardless of ad metaphors. In contrast, prevention‐focused consumers with low brand commitment exhibit more favorable attitudes toward competitor brands advocated by highly metaphorical ads than those advocated by low metaphorical ads. Moreover, promotion‐focused consumers exhibit more favorable attitudes toward competitor brands advocated by highly metaphorical ads than those advocated by low metaphorical ads, regardless of brand commitment.