Phylogenetic comparison on cognition: Advances in evolutionary psychology

More and more biological evidence has been yielded in support of physical evolution of species. In contrast, psychological evolution has been, so far, studied primarily with theoretical exploration. There are two theoretical approaches to the evolution on cognitive ability. The first, Common Ancestor, states that all species, including humans, have a common ancestor, from whom particular cognitive abilities in all existing species are inherited. The second, Evolutionary Convergence holds that different species possess similar cognitive abilities. The controversy between the two theories lies in the explanation of similar cognitive abilities in different species, one focusing on theoretical deduction and the other on parsimony in interpretation. However, both agree that basic cognitive abilities can be a starting point for studying the evolution on cognitive abilities. The top-down and the bottom-up approaches are usually used to study the cognitive abilities of different species. The top-down approach focuses on the cross-species levels of presence of a certain cognitive ability, and explores its level of presence among different species in relation to that in human beings. For the bottom-up approach, researchers generally analyze and study basic cognitive abilities, or the basic components of complex cognitive abilities, and systematically study the degree of difference between species in these basic cognitive abilities, which are universally present across species. The top-down approach can provide a precondition for defining the species boundaries of certain cognitive abilities, or which species have such abilities, while the bottom-up approach employs systematic methods to study the basic components of relevant cognitive abilities through cross-species experiments. The elaboration above suggests that we can understand the emergence and development of certain cognitive abilities, and the relationship between human’s advanced and basic cognitive abilities from the perspective of phylogenesis. Phylogenetic comparative methods are an important kind of bottom-up method. For a basic cognitive ability, the method of phylogenetic comparison is used to conduct cross-species experiments, so that the data obtained can be compared systematically. The results are of great significance for answering theoretical questions regarding cognitive evolution. For example, Amici and colleagues examined the ability of social inhibitory control in six primates (chimpanzees, bonobos, orangutans, gorillas, capuchin monkeys, and spider monkeys), and found that the level of fission-fusion dynamics could partially predict this ability. MacLean and colleagues studied the inhibitory control of 567 individuals from 36 species (birds and mammals), and showed that inhibitory control was positively correlated with absolute brain volume. Dietary breadth also predicted inhibitory control in the primate species studied. Jones and colleagues tested numerical cognition in three lemurs ( Lemur catta , Eulemur mongoz , and Eulemur Macaco flavifrons ), rhesus monkeys ( Macaca mulatta ), and human adults. They did not find any difference in nature among the four non-human groups in this ability. Specifically, the internal representation by all four non-humans was as predicted by the approximate number system and fit the linear representation model of the system. Cognitive differences among the five groups mainly lied in their numerical acuity, with humans having the lowest Weber fractions and the highest sensitivity. Chen improved their methods, tested humans in five age groups and golden snub-nosed monkeys ( Rhinopithecus roxellana ), and obtained findings consistent with those of the previous study. With the rise of cross-species systematic comparison, the latest trend of in-depth exploration into cognitive ability, research on phylogenesis on cognitive ability has entered a quantitative stage. Quantitative research on the relationship between evolutionary adaptive pressure and cognitive ability will help reveal patterns in the emergence and development on cognitive abilities in different species and even human beings.