Abstract: An experimental study of search-image use by araneophagic jumping spiders (i.e., salticid spiders that prey routinely on other spiders) supports five conclusions. First, araneophagic salticids have an innate predisposition to form search images for specific prey from their preferred prey category (spiders) rather than for prey from a non-preferred category (insects). Second, single encounters are sufficient for forming search images. Third, search images are based on selective attention specifically to optical cues. Fourth, there are trade-offs in attention during search-image use (i.e., forming a search image for one type of spider diminishes the araneophagic salticid's attention to other spiders). Fifth, the araneophagic salticid's adoption of search images is costly to the prey (i.e., when the araneophagic salticid adopts a search, the prey's prospects for surviving encounters with the araneophagic salticid are diminished). Cognitive and ecological implications of search-image use are discussed.

Abstract: Humans use memory awareness to determine whether relevant knowledge is available before acting, as when we determine whether we know a phone number before dialing. Such metacognition, or thinking about thinking, can improve selection of appropriate behavior. We investigated whether rhesus monkeys ( Macaca mulatta) are capable of a simple form of metacognitive access to the contents of short-term memory. Monkeys chose among four opaque tubes, one of which concealed food. The tube containing the reward varied randomly from trial to trial. On half the trials the monkeys observed the experimenter baiting the tube, whereas on the remaining trials their view of the baiting was blocked. On each trial, monkeys were allowed a single chance to select the tube containing the reward. During the choice period the monkeys had the opportunity to look down the length of each tube, to determine if it contained food. When they knew the location of the reward, most monkeys chose without looking. In contrast, when ignorant, monkeys often made the effort required to look, thereby learning the location of the reward before choosing. Looking improved accuracy on trials on which monkeys had not observed the baiting. The difference in looking behavior between trials on which the monkeys knew, and trials on which they were ignorant, suggests that rhesus monkeys discriminate between knowing and not knowing. This result extends similar observations made of children and apes to a species of Old World monkey, suggesting that the underlying cognitive capacities may be widely distributed among primates.

Abstract: Tool use and transport represent cognitively important aspects of early hominid evolution, and nonhuman primates are often used as models to examine the cognitive, ecological, morphological and social correlates of these behaviors in order to gain insights into the behavior of our early human ancestors. In 2001, Jalles-Filho et al. found that free-ranging capuchin monkeys failed to transport tools (stones) to food sites (nuts), but transported the foods to the tool sites. This result cast doubt on the usefulness of Cebus to model early human tool-using behavior. In this study, we examined the performance of six captive tufted capuchin monkeys (Cebus apella) in a tool transport task. Subjects were provided with the opportunity to transport two different tools to fixed food reward sites when the food reward was visible from the tool site and when the food reward was not visible from the tool site. We found that the subjects quickly and readily transported probing tools to an apparatus baited with syrup, but rarely transported stones to a nut-cracking apparatus. We suggest that the performance of the capuchins here reflects an efficient foraging strategy, in terms of energy return, among wild Cebus monkeys.

Abstract: The ability of organisms to discriminate social signals, such as affective displays, using different sensory modalities is important for social communication. However, a major problem for understanding the evolution and integration of multimodal signals is determining how humans and animals attend to different sensory modalities, and these different modalities contribute to the perception and categorization of social signals. Using a matching-to-sample procedure, chimpanzees discriminated videos of conspecifics' facial expressions that contained only auditory or only visual cues by selecting one of two facial expression photographs that matched the expression category represented by the sample. Other videos were edited to contain incongruent sensory cues, i.e., visual features of one expression but auditory features of another. In these cases, subjects were free to select the expression that matched either the auditory or visual modality, whichever was more salient for that expression type. Results showed that chimpanzees were able to discriminate facial expressions using only auditory or visual cues, and when these modalities were mixed. However, in these latter trials, depending on the expression category, clear preferences for either the visual or auditory modality emerged. Pant-hoots and play faces were discriminated preferentially using the auditory modality, while screams were discriminated preferentially using the visual modality. Therefore, depending on the type of expressive display, the auditory and visual modalities were differentially salient in ways that appear consistent with the ethological importance of that display's social function.