Showing papers in "Journal of Comparative Psychology in 2004"
TL;DR: Bonobos, chimpanzees, gorillas, and orangutans were presented with 2 cups and understood that the food caused the noise, not simply that the noise was associated with the food.
Abstract: Bonobos (Pan paniscus; n = 4), chimpanzees (Pan troglodytes; n = 12), gorillas (Gorilla gorilla; n = 8), and orangutans (Pongo pygmaeus; n = 6) were presented with 2 cups (1 baited) and given visual or auditory information about their contents. Visual information consisted of letting subjects look inside the cups. Auditory information consisted of shaking the cup so that the baited cup produced a rattling sound. Subjects correctly selected the baited cup both when they saw or heard the food. Nine individuals were above chance in both visual and auditory conditions. More important, subjects as a group selected the baited cup when only the empty cup was either shown or shaken, which means that subjects chose correctly without having seen or heard the food (i.e., inference by exclusion). Control tests showed that subjects were not more attracted to noisy cups, avoided shaken noiseless cups, or learned to use auditory information as a cue during the study. It is concluded that subjects understood that the food caused the noise, not simply that the noise was associated with the food.
210 citations
TL;DR: Group living in the semiarid succulent karoo of South Africa is possibly due to ecological constraints imposed by habitat saturation because of a year-round stable food supply as well as associated benefits of philopatry.
Abstract: The authors studied the striped mouse (Rhabdomys pumilio) in the semiarid succulent karoo of South Africa. Mice forage alone, but they live in groups that share a common nest. Groups consist of 1 to 4 breeding females, 1 to 2 breeding males, and their offspring of both sexes, which remain in their natal group even after reaching adulthood, participating in territorial defense and nest building without showing signs of reproductive activity. Interactions are typically amicable and take place inside or in front of the nest. In contrast, encounters with mice from other groups are aggressive. Group living in the succulent karoo is possibly due to ecological constraints imposed by habitat saturation because of a year-round stable food supply as well as associated benefits of philopatry.
174 citations
TL;DR: The capacity for nonverbal reference may predate the Hominidae-Pongidae split, and the development of non verbal reference may be independent of human species-specific adaptations for speech.
Abstract: Two experiments were conducted to assess the referential function of chimpanzee (Pan troglodytes) gestures to obtain food. The chimpanzees received 1 trial per condition. In Experiment 1 (N 101), in full view of the chimpanzee, a banana was placed on top of 1 of 2 inverted buckets or was hidden underneath 1 of the buckets. In Experiment 2 (N 35), 4 conditions were presented in constant order:(a) no food, no observer; (b) no food, observer present; (c) food present, no observer; and (d) food present, observer present. Gestures and visual orienting were used socially and referentially. The capacity for nonverbal reference may predate the HominidaePongidae split, and the development of nonverbal reference may be independent of human species-specific adaptations for speech.
159 citations
TL;DR: Two chimpanzees (Pan troglodytes) made numerousness judgments of nonvisible sets of items and were more dependent on factors indicative of an analogue-magnitude mechanism for representation of set size than on an object file mechanism.
Abstract: Two chimpanzees (Pan troglodytes) made numerousness judgments of nonvisible sets of items. In Experiment 1, 1-10 items were dropped 1 at a time into an opaque cup, and then an additional 1-10 items were dropped 1 at a time into another opaque cup. The chimpanzees' performance levels were high and were more dependent on factors indicative of an analogue-magnitude mechanism for representation of set size than on an object file mechanism. In Experiment 2, a 3rd visible set was made available after the sequential presentation of the first 2 sets. The chimpanzees again performed at high levels in selecting the largest of the 3 sets. In Experiment 3, 1 of the 2 initially presented sets was reduced in number by the sequential removal of 1, 2, or 3 items. Both chimpanzees performed above chance levels for the removal of 1, but not more than 1, item.
143 citations
TL;DR: Results suggest that the geometric properties of the spatial arrangement and discrete landmarks are sensitive to encoding in a maplike or relational system, whereas different sources of spatial information are encoded in a single and flexible representation of the environment.
Abstract: Goldfish (Carassius auratus) were trained in different place-finding tasks as a means of analyzing their ability to encode the geometric and the featural properties of the environment. Results showed that goldfish could encode and use both geometric and featural information to navigate. Goldfish trained in a maplike, or relational, procedure encoded both types of information in a single representation. In contrast, fish trained in a directly cued procedure developed 2 independent and competing strategies. These results suggest that the geometric properties of the spatial arrangement and discrete landmarks are sensitive to encoding in a maplike or relational system, whereas different sources of spatial information are encoded in a single and flexible representation of the environment.
128 citations
TL;DR: Additive effects were evident, showing how environmental factors may modulate behavioral traits, and how the environment may intervene in determining individual behavioral characteristics, in Equus caballus.
Abstract: The aim of the present study was to broach the question of the relative influence of different genetic and environmental factors on different temperament/personality traits of horses (Equus caballus). The researchers submitted 702 horses to standardized experimental tests and investigated 9 factors, either genetic or environmental. Genetic factors, such as sire or breed, seemed to influence more neophobic reactions, whereas environmental factors, such as the type of work, seemed to play a more dominant role in reactions to social separation or learning abilities. Additive effects were evident, showing how environmental factors may modulate behavioral traits. This study constitutes a first step toward understanding the relative weights of genetic factors and how the environment may intervene in determining individual behavioral characteristics.
128 citations
TL;DR: The ability of lambs (Ovis aries) to evaluate an event according to 3 criteria through 3 tests support the usefulness of appraisal theories to assess emotion in animals.
Abstract: Appraisal theories provide a framework that gives insight into emotions and could allow comparisons across species. According to these theories, events are first evaluated on their suddenness, novelty, and unpredictability. The authors examined the ability of lambs (Ovis aries) to evaluate an event according to these 3 criteria through 3 tests. The lambs responded to suddenness with a startle response coupled with an increase in heart rate and to novelty with an orientation response coupled with an increase of vagal activity. There was no clear evidence that lambs can detect the predictability of an event. Those results support the usefulness of appraisal theories to assess emotion in animals.
114 citations
TL;DR: Sp spontaneous understanding of human gaze accomplished through head orientation is revealed, with or without the human informant's eyes obscured, and it is demonstrated that gaze-directed cues were as effective as point- directed cues in the object-choice task.
Abstract: The authors tested 2 bottlenosed dolphins (Tursiops truncatus) for their understanding of human-directed gazing or pointing in a 2-alternative object-choice task. A dolphin watched a human informant either gazing at or pointing toward 1 of 2 laterally placed objects and was required to perform a previously indicated action to that object. Both static and dynamic gaze, as well as static and dynamic direct points and cross-body points, yielded errorless or nearly errorless performance. Gaze with the informant's torso obscured (only the head was shown) produced no performance decrement, but gaze with eyes only resulted in chance performance. The results revealed spontaneous understanding of human gaze accomplished through head orientation, with or without the human informant's eyes obscured, and demonstrated that gaze-directed cues were as effective as point-directed cues in the object-choice task.
105 citations
TL;DR: The results show that the main factor of a successful human demonstration is the continuous verbal communication with the dog during detouring, and provide evidence that in adult dogs, communicative context with humans is needed for effective interspecific social learning to take place.
Abstract: Pet dogs (Canis familiaris) learn to detour a V-shaped fence effectively from an unfamiliar human demonstrator. In this article, 4 main features of the demonstrator's behavior are highlighted: (a) the manipulation of the target, (b) the familiarity of the demonstrator, (c) the role of verbal attention-getting behavior, and (d) whether a strange trained dog could also be an effective demonstrator. The results show that the main factor of a successful human demonstration is the continuous verbal communication with the dog during detouring. It was also found that an unfamiliar dog demonstrator was as efficient as the unfamiliar experimenter. The experiments provide evidence that in adult dogs, communicative context with humans is needed for effective interspecific social learning to take place.
104 citations
TL;DR: The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy, and found capuchin monkeys seem to pay more attention in a social situation involving novel tokens.
Abstract: Social learning is assumed to underlie traditions, yet evidence indicating social learning in capuchin monkeys (Cebus apella), which exhibit traditions, is sparse. The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy. Capuchins change their preferences in favor of a token worth a high-value food reward after watching a conspecific model exchange 2 differentially rewarded tokens, yet they fail to develop a similar preference after watching tokens paired with foods in the absence of a conspecific model. They also fail to learn that the value of familiar tokens has changed. Information about token value is available in all situations, but capuchins seem to pay more attention in a social situation involving novel tokens.
96 citations
TL;DR: It is suggested that juvenile chimpanzees increase play signaling to prevent termination of the play bouts by mothers of younger partners, particularly as the intensity of play bouts increases.
Abstract: Prescriptive social rules are enforced statistical regularities. The authors investigated whether juvenile chimpanzees (Pan troglodytes) recognize and use enforced statistical regularities to guide dyadic play behavior. They hypothesized (a) that proximity of adults, especially mothers of younger play partners, to play bouts will increase the play signaling of older partners and (b) that when juvenile-juvenile play bouts occur in proximity to adults, older partners will play at a lower intensity than when no adults are present. They found that older and younger partners increase their play signaling in the presence of the mothers of younger partners, particularly as the intensity of play bouts increases. In contrast to their hypothesis, older partners played more roughly when the mothers of younger partners were in proximity. These results suggest that juvenile chimpanzees increase play signaling to prevent termination of the play bouts by mothers of younger partners.
TL;DR: Results suggest that the search behavior of dogs was guided by simple associative rules rather than mental representation of the object's past trajectory.
Abstract: Domestic dogs (Canis familiaris) perform above chance on invisible displacement tasks despite showing few other signs of possessing the necessary representational abilities. Four experiments investigated how dogs find an object that has been hidden in 1 of 3 opaque boxes. Dogs passed the task under a variety of control conditions, but only if the device used to displace the object ended up adjacent to the target box after the displacement. These results suggest that the search behavior of dogs was guided by simple associative rules rather than mental representation of the object's past trajectory. In contrast, Experiment 5 found that on the same task, 18- and 24-month-old children showed no disparity between trials in which the displacement device was adjacent or nonadjacent to the target box.
TL;DR: There was a decrease in the global degree of sharing over the years and greater changes were observed after social disturbance.
Abstract: Although vocal sharing is widespread at several phylogenetic levels, few descriptions concerned primates. The present study involved the dynamics of vocal structures and social organization in a captive group of Campbell's monkeys (Cercopithecus campbelli campbelli) at 3-year periods, using precise sound recording and comparison. The authors focused on combined harmonic 6 calls, often involved in vocal exchanges and associated with approaches. Each female produced 1 to 4 variants, shared, or not, between individuals. Changes appeared between years in the form of disappearance, appearance, or transformation of variants. There was a decrease in the global degree of sharing over the years. Greater changes were observed after social disturbance. Sharing would be more important in disturbed than stable groups to advertise bonds.
TL;DR: Human listeners at all levels of experience and affinity for cats rated domestic cat meows as far more pleasant sounding than wild cat vocalizations, consistent with a model of cat domestication that posits selective pressure on meows based on human perceptual biases.
Abstract: To test for possible anthropogenic selection effects on meows in domestic felids, vocalizations by domestic cats (Felis catus) were compared with cries by their closest wild relative, the African wild cat (Felis silvestris lybica). Comparisons included analysis of acoustic characteristics and perceptual studies with human (Homo sapiens) listeners. The perceptual studies obtained human listener ratings of call pleasantness. Both the acoustic and perceptual comparisons revealed clear species-level differences: The domestic cat meows were significantly shorter in mean duration than the wild cat meows, showed higher mean formant frequencies, and exhibited higher mean fundamental frequencies. Human listeners at all levels of experience and affinity for cats rated domestic cat meows as far more pleasant sounding than wild cat vocalizations. These results are consistent with a model of cat domestication that posits selective pressure on meows based on human perceptual biases.
TL;DR: The performances of at least 2 subjects that achieved very high scores up to the successive invisible displacement task suggest that this species is able to represent the existence and the movements of unperceived objects.
Abstract: A series of 9 search tasks corresponding to the Piagetian Stages 3-6 of object permanence were administered to 11 common marmosets (Callithrix jacchus). Success rates varied strongly among tasks and marmosets, but the performances of most subjects were above chance level on the majority of tasks of visible and invisible displacements. Although up to 24 trials were administered in the tests, subjects did not improve their performance across trials. Errors were due to preferences for specific locations or boxes, simple search strategies, and attentional deficits. The performances of at least 2 subjects that achieved very high scores up to the successive invisible displacement task suggest that this species is able to represent the existence and the movements of unperceived objects.
TL;DR: The results suggest that, like a gorilla, orangutans can learn concepts at each level of abstraction, and unlike other nonhumans, most of these subjects rapidly learned the intermediate level discrimination.
Abstract: Levels of abstraction have rarely been manipulated in studies of natural concept formation in nonhumans. Isolated examples have indicated that animals, relative to humans, may learn concepts at varying levels of abstraction with differential ease. The ability of 6 orangutans (Pongo abelii) of various ages to make natural concept discriminations at 3 levels of abstraction was therefore investigated. The orangutans were rewarded for selecting photos of orangutans instead of humans and other primates (concrete level), primates instead of other animals (intermediate level), and animals instead of nonanimals (abstract level) in a 2-choice touch screen procedure. The results suggest that, like a gorilla (Gorilla gorilla gorilla) tested previously (Vonk & MacDonald, 2002), orangutans can learn concepts at each level of abstraction, and unlike other nonhumans, most of these subjects rapidly learned the intermediate level discrimination.
TL;DR: Attentional focusing on preferred partners appears the most likely explanation for differences found in song acquisition in relation to experience, sex, and song categories.
Abstract: Social influence on song acquisition was studied in 3 groups of young European starlings raised under different social conditions but with the same auditory experience of adult song. Attentional focusing on preferred partners appears the most likely explanation for differences found in song acquisition in relation to experience, sex, and song categories. Thus, pair-isolated birds learned from each other and not from broadcast live songs, females did not learn from the adult male tutors, and sharing occurred more between socially associated peers. On the contrary, single-isolated birds clearly copied the adult songs that may have been the only source of attention stimulation. Therefore, social preference appears as both a motor for song learning and a potential obstacle for acquisition from nonpreferred partners, including adults.
TL;DR: Transformation tests revealed that participants used the color and shape of distinct features to encode the goal's position, and participants trained with features spontaneously encoded the geometric information.
Abstract: Adults searched for a goal in images of a rectangular environment. The goal’s position was constant relative to featural and geometric cues, but the absolute position changed across trials. Participants easily learned to use the featural cues to find the target, but learning to use only geometric information was difficult. Transformation tests revealed that participants used the color and shape of distinct features to encode the goal’s position. When the features at the correct and geometrically equivalent corners were removed, participants could use distant features to locate the goal. Accuracy remained above chance when a single distant feature was present, but the feature farthest from the goal yielded lower accuracy than one closer. Participants trained with features spontaneously encoded the geometric information. However, this representation did not withstand orientation transformations. One important step for successful navigation is determining the appropriate direction to travel. This has been referred to as determining one’s heading (Gallistel, 1990). Research has shown that animals may use many different mechanisms and environmental cues to accurately orient, including self-referencing systems such as path integration and external referencing systems based on landmarks or environmental geometry (e.g., Healy, 1998). However, if self-referencing systems are disrupted and the animal is disoriented (e.g., by rotation), the animal will need to rely on external cues to reorient. Several studies have suggested that external landmarks and/or the overall geometric shape of the environment may be used in this process of reorienting (Cheng, 1986; Cheng & Gallistel, 1984).
TL;DR: Findings substantiate the adaptive role of several spatial sex differences in humans and establish whether navigation patterns are associated with a broader set of spatial abilities in men than in women.
Abstract: In mammals, spatial sex differences may have coevolved with sex differences in the size of home ranges. This study first evaluated whether, in keeping with most mammals and traditional human (Homo sapiens) societies, home ranges are larger in male than in female Westerners. Second, it established whether navigation patterns are associated with a broader set of spatial abilities in men than in women. Results showed that current male home ranges surpass female home ranges. Ranging was also positively correlated with achievement in tests of mental rotation, surface development, and location memory among men only, whereas it was associated with embedded figures scores in both sexes. Overall, these findings substantiate the adaptive role of several spatial sex differences in humans.
TL;DR: Overall, the data suggest that capuchins can form abstract, conceptual-like representations for above and below spatial relations.
Abstract: Using a matching-to-sample procedure, the researchers investigated tufted capuchins' (Cebus apella) ability to form categorical representations of above and below spatial relations. In Experiment 1, 5 capuchins correctly matched bar-dot stimuli on the basis of the relative above and below location of their constituent elements. The monkeys showed a positive transfer of performance both when the bar-dot distance in the two comparison stimuli differed from that of the sample and when the actual location of the matching stimulus and the nonmatching stimulus on the apparatus was modified. In Experiment 2, the researchers systematically changed the shapes of the located object (the dot) or the reference object (the horizontal bar). These manipulations did not affect the monkeys' performance. Overall, the data suggest that capuchins can form abstract, conceptual-like representations for above and below spatial relations.
TL;DR: It is indicated that chimpanzees have some intuition about support phenomena but their sensitivity to relational object properties may differ from that of human infants (Homo sapiens) in this domain.
Abstract: Using looking-time measures, the authors examined untrained chimpanzees' (Pan troglodytes) ability to distinguish between adequate and inadequate support. In 3 experiments, the chimpanzees' sensitivity to different support relations between 2 objects was assessed. In each experiment, the chimpanzees saw a possible and an impossible test event, presented as digital video clips. Looking times in the 3 experiments suggest that chimpanzees use amount of contact between 2 objects, but not type of contact, to distinguish between adequate and inadequate support relations. These results indicate that chimpanzees have some intuition about support phenomena but their sensitivity to relational object properties may differ from that of human infants (Homo sapiens) in this domain.
TL;DR: Pigeons (Columba livia) searched for a hidden target area in images showing a schematic rectangular environment with constant relative to distinctive featural cues and geometric properties of the environment.
Abstract: Pigeons (Columba livia) searched for a hidden target area in images showing a schematic rectangular environment. The absolute position of the goal varied across trials but was constant relative to distinctive featural cues and geometric properties of the environment. Pigeons learned to use both of these properties to locate the goal. Transformation tests showed that pigeons could use either the color or shape of the features, but performance was better with color cues present. Pigeons could also use a single featural cue at an incorrect corner to distinguish between the correct corner and the geometrically equivalent corner; this indicates that they did not simply use the feature at the correct corner as a beacon. Interestingly, pigeons that were trained with features spontaneously encoded geometry. The encoded geometric information withstood vertical translations but not orientation transformations.
TL;DR: Pigeons (Columba livia) searched for food hidden in the center of a square enclosure on control and corner tests, suggesting relative-distance encoding and contrast with previous results on pigeons' responses to expansions of discrete landmark arrays.
Abstract: Pigeons (Columba livia) searched for food hidden in the center of a square enclosure. On occasional tests without food, the enclosure was (a) unchanged from training (control tests), (b) moved to different corners of the testing room (corner tests), or (c) doubled in size (expansion tests). The birds showed localized search in the center of the enclosure on control and corner tests. On expansion tests, some birds searched near the center of the enclosure, suggesting relative-distance encoding. Other birds searched at locations that maintained the training distance from walls, suggesting absolute-distance encoding. These results are consistent with previous studies on chicks (Gallus gallus) in similar enclosures and contrast with previous results on pigeons' responses to expansions of discrete landmark arrays.
TL;DR: The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system.
Abstract: The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system.
TL;DR: It is proposed that the possible contagion of scratching by monkeys observing another's scratching may involve transmission of a psychological state, a primitive style of empathy.
Abstract: Although a large number of studies have examined self-directed behaviors (SDBs) such as scratching and self-grooming as nonverbal leakage of negative emotional arousal in humans, few studies have investigated the informative function of SDBs in nonhuman primates. The present study investigated whether viewing another monkey scratching itself elicited negative arousal from conspecific observers in Japanese monkeys (Macaca fuscata). An experimental situation was created in which the target monkey watched a stranger through a small peephole and the observer monkey(s) watched the target in turn. Scratching spread when conspecific observers watched the target scratching itself while performing monitoring behavior. The author proposes that the possible contagion of scratching by monkeys observing another's scratching may involve transmission of a psychological state, a primitive style of empathy.
TL;DR: Both humans and the PCA produced the same asymmetry in kin recognition as found with the chimpanzees, and suggested that the asymmetry was a function of differences in the distribution of global characteristics associated with the framing of the faces in the son and daughter test sets.
Abstract: The male-offspring biased visual kin recognition in chimpanzees (Pan troglodytes) reported by L. A. Parr and F. B. M. de Waal (1999) was replicated with human (Homo sapiens) participants and a principal components analysis (PCA) of pixel maps of the chimpanzee face photos. With the same original materials and methods, both humans and the PCA produced the same asymmetry in kin recognition as found with the chimpanzees. The PCA suggested that the asymmetry was a function of differences in the distribution of global characteristics associated with the framing of the faces in the son and daughter test sets. Eliminating potential framing biases, either by cropping the photos tightly to the faces or by rebalancing the recognition foils, eliminated the asymmetry but not human participants' ability to recognize chimpanzee kin.
TL;DR: The results suggest Japanese macaque mothers may be unable to understand their offspring's need for distress alleviation after the receipt of aggression, and cognitive empathic responses in a naturalistic setting are evaluated.
Abstract: The authors of this study investigated the behavioral and emotional response of female Japanese macaques (Macaca fuscata) to an aggression received by their offspring to evaluate the existence of cognitive empathic responses in a naturalistic setting. After their offspring received an aggression, mothers did not direct increased affiliative contacts to them. The factors likely to affect the degree of distress in the offspring or the perceived risk for the mother failed to appropriately modulate maternal behavior. Finally, mothers did not increase their frequency of scratching (a behavioral indicator of anxiety) after their offspring had received an aggression. The results suggest Japanese macaque mothers may be unable to understand their offspring's need for distress alleviation after the receipt of aggression.
TL;DR: There was strong evidence of transposition at group level, although individual differences in bias toward the smaller quantities became apparent, suggesting robustness in the operations required for this form of self-control.
Abstract: Squirrel monkeys (Saimiri sciureus) that had learned to reach toward 1 piece of food instead of 4 in a reverse-reward contingency were tested after an 8-month delay with no intervening relevant experiences. All monkeys except 1 continued to show inhibitory control by reliably reaching toward the smaller quantity, most of them doing so within 2 sessions. Performance was maintained when a low-preference food replaced prized foods as arrays and rewards. When the quantities 1 and 4 were replaced with different ones, there was strong evidence of transposition at group level, although individual differences in bias toward the smaller quantities became apparent. Individual differences in mastering the original task more than 8 months previously were quite stable, suggesting robustness in the operations required for this form of self-control.
TL;DR: Two young gray seals were trained successfully to demonstrate the first 2 levels of usage learning, but novel moan and growl stimuli tended to elicit growls, casting doubt on the possibility that gray seals can reach the 4th level.
Abstract: Call usage learning can be demonstrated on 4 different levels: signaling on command, signaling and refraining from signaling on command, responding to a trained stimulus with a signal from a specific signal class, and responding to the playback of any untrained stimulus with one from the same signal class. Two young gray seals (Halichoerus grypus) were trained successfully to demonstrate the first 2 levels. They also learned to respond to 9 moan stimuli and 9 growl stimuli with vocalizations of the same class (Level 3). However, novel moan and growl stimuli tended to elicit growls. This casts doubt on the possibility that gray seals can reach the 4th level, but it demonstrates that they are capable of the first 3 levels of usage learning.
TL;DR: Dominant males had better spatial-learning ability and tended to have quicker learning speed but did not have better spatial memory than less aggressive subordinates, and the authors found no evidence that contest and scramble competition have favored alternative reproductive phenotypes among male meadow voles.
Abstract: Males of many mammalian species exhibit contest competition and scramble competition for mates, but the relationship between these 2 forms of competition remains poorly understood. The authors measured dominance rank and spatial ability as traits likely to be selected by contest and scramble competition, respectively, among male meadow voles (Microtus pennsylvanicus). The spatial ability of males was assessed using water maze tests, and dominance rank was determined using paired trials in a neutral arena. Dominant males had better spatial-learning ability and tended to have quicker learning speed but did not have better spatial memory than less aggressive subordinates. Therefore, the authors found no evidence that contest and scramble competition have favored alternative reproductive phenotypes among male meadow voles.