The evolution of self-control.

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution.

Breed Differences in Dopamine Receptor D4 Gene (DRD4) in Horses.

Genetic polymorphisms in genes related to neurotransmitters or hormones affect personality or behavioral traits in many animal species including humans. In domestic animals, the allele frequency of such genes has been reported to be different among breeds and it may account for breed differences in behavior. In this study, we investigated breed differences in horses in the dopamine receptor D4 gene (DRD4), which has been reported to affect horse personality. We collected samples from seven horse breeds including those native to Japan and Korea, and compared the sequence of the DRD4 exon3 region among these breeds. We found that there were two types of polymorphisms (VNTR and SNPs) in the exon3 region, and some of them seemed to be breed-specific. In addition, we found that the allele frequency of G292A, reported to be associated with horse personality, differed greatly between native Japanese horses and Thoroughbred horses. The frequency of the A allele which is associated with low curiosity and high vigilance, was much lower in native Japanese horses (Hokkaido, 0.03; Taishu, 0.08) than in Thoroughbreds (0.62). This difference may account for breed differences in personality or behavioral traits. Further studies of the function of these polymorphisms and their effect on behavior are indicated.

Acute toxicity of ammonia and nitrite to Siamese fighting fish (Betta splendens).

The acute toxicity and sublethal effects of ammonia and nitrite on the air-beathing Siamese fighting fish, betta (Betta splendens) was studied for 96 h. The LC50 (50% Lethal Concentration) for 96 h for adult bettas to ammonia-N and nitrite-N was 123.4 mM (1.7 g/L, 95% confidence limits: 114.7-130.0 mM) and 24.6 mM (343.6 mg/L, 95% confidence limits: 22.7-26.4 mM) respectively. Exposure to 90 mM ammonia did not affect ammonia and urea excretion rates in bettas. There was no significant difference in values between control and ammonia-loaded (90 mM ammonia) individuals in either brain or liver activities of glutamine synthase, while plasma ammonia levels slightly increased. It appears unlikely that ammonia was converted to urea or amino acids for detoxification. Sublethal nitrite (24.6 mM nitrite) affected plasma nitrite, methemoglobin and hemoglobin. Plasma nitrite values remained much lower than ambient concentrations. Betta has a labyrinth organ and can breathe air. Bettas may temporarily reduce the entry of ammonia and nitrite into the body by increasing the rate of air respiration and reducing the contribution of the gill epithelium, which is highly permeable to these nitrogenous pollutants.

I acknowledge your help: capuchin monkeys' sensitivity to others' labor.

Our society is sustained by wide-ranging cooperation. If individuals are sensitive to others' gains and losses as well as the amount of labor, they can ensure future beneficial cooperative interaction. However, it is still an open question whether nonhuman primates are sensitive to others' labor. We asked this question in tufted capuchin monkeys in an experimental food-sharing situation by comparing conditions with labor by two participants equalized (Equal labor condition) or unequalized (Unequal labor condition). The operator monkey pulled the drawer of one of the two food containers placed between two monkeys, each containing a food for him/herself and another for the recipient monkey. The recipient 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. In Unequal labor condition, the operator first had to pull the handle of the board to which the containers were glued and then pull the drawer of one of the containers, while the recipient received food with no labor. In Equal labor condition, the recipient had to pull the handle of the board so that the operator could operate a container. Results showed that operators chose the high-value food container for recipients more often than when the recipient was absent only in Equal labor condition. This suggests that capuchin monkeys are sensitive to others' labor and actively give food to a partner who has helped them to complete a task.

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.

Third-party social evaluations of humans by monkeys and dogs.

Developmental psychologists are increasingly interested in young children's evaluations of individuals based on third-party interactions. Studies have shown that infants react negatively to agents who display harmful intentions toward others, and to those who behave unfairly. We describe experimental studies of capuchin monkeys' and pet dogs' differential reactions to people who are helpful or unhelpful in third-party contexts, and monkeys' responses to people who behave unfairly in exchanges of objects with a third party. We also present evidence that capuchin monkeys monitor the context of failures to help and violations of reciprocity, and that intentionality is one factor underlying their social evaluations of individuals whom they see interacting with others. We conclude by proposing some questions for studies of nonhuman species' third party-based social evaluations.

A new diatom growth inhibition assay using the XTT colorimetric method.

Marine biofouling, which leads to significant operational stress and economic damage on marine infrastructures, is a major problem in marine related industries. Currently, the most common way to avoid marine biofouling involves the use of biocidal products in surface coatings. However, the need for environmentally friendly antibiofouling compounds has increased rapidly with the recent global prohibition of harmful antifoulants, such as tributyltin (TBT). In particular, periphytic diatoms have been shown to contribute significantly to biofilms, which play an important role in biofouling. Therefore, inhibiting the proliferation of fouling diatoms is a very important step in the prevention of marine biofouling. In this study, we developed a new, rapid, accurate, and convenient growth inhibition assay using the XTT colorimetric method to prevent the growth of the fouling periphytic diatom, Nitzschia amabilis Hidek. Suzuki (replaced synonym, Nitzschia laevis Hustedt). The feasibility of this method was verified by determining the growth inhibition activities of two standard photosynthetic inhibitors, DCMU and CuSO4. However, neither inhibitor had any cytotoxic activities at the range of concentrations tested. Moreover, this method was applied by screening and purification of herbicidic but non-cytotoxic compounds from cyanobacteria extracts. Our results demonstrate the utility of this newly established growth inhibition assay for the identification of marine anti-biofouling compounds.

Capuchin monkeys judge third-party reciprocity.

Increasing interest is being shown in how children develop an understanding of reciprocity in social exchanges and fairness in resource distribution, including social exchanges between third parties. Although there are descriptions of reciprocity on a one-to-one basis in other species, whether nonhumans detect reciprocity and violations of reciprocity between third parties is unknown. Here we show that capuchin monkeys discriminate between humans who reciprocate in a social exchange with others and those who do not. Monkeys more readily accepted food from reciprocators than non-reciprocators or partial reciprocators. However, when exchange asymmetry was due to one partner starting out with fewer goods, the initially impoverished reciprocator was not discriminated against. These results indicate that the cognitive or emotional prerequisites for judging reciprocity in third-party social exchanges exist in at least one other primate species.

Third-party social evaluation of humans by monkeys.

Humans routinely socially evaluate others not only following direct interactions with them but also based on others' interactions with third parties. In other species, 'eavesdropping' on third-party interactions is often used to gain information about foraging or mating opportunities, or others individuals' aggressiveness or fighting ability. However, image scoring for potential cooperativeness is less well studied. Here we ask whether a non-human primate species, tufted capuchin monkeys (Cebus apella), socially evaluates humans after witnessing third-party interactions involving a helpful intervention or failure to help. We find that the monkeys accept food less frequently from those who persistently reject another's requests for help. This negative social evaluation effect is robust across conditions, and tightly linked to explicit refusal to help. Evaluation of potential helpfulness based on third-party interactions may thus not be unique to humans.