Among Darwin’s brilliant ideas was his (1871) conception of animal communication signals as adaptive characteristics of a species. The idea was subsequently taken up by the ethologists of Europe in the 1930s (Lorenz, Tinbergen, and von Frisch in particular) in their studies of animal signaling systems in nature. For many subsequent researchers, human language was the implicit model for an animal communication system. Although not expecting the same level of complexity, these researchers assumed that animal signals transmitted information from sender to receiver that was honest, and that benefitted them both. However, the honest signaling/mutual benefit view was challenged by new researchers steeped in the sociobiology and behavioral ecology movement of the 1960s. The emphasis on competition in this new field inspired these researchers to reconceive the animal signaling process as one in which the sender manipulates the receiver to the sender’s advantage. This view was challenged in turn when researchers recognized that the receiver was not a passive party in the interaction, but fully capable of manipulating the sender to its advantage. The communication interaction can be viewed as an arm’s race. The handicap principle—the idea that honesty in signaling can be maintained if signals are costly—is one way the receiver may gain an edge in this competition. Eventually, game theory considerations led to the development of a revised perspective in which signals evolve only when both the sender and the receiver benefit on average, and where signals are honest on average. Researchers examining a particular signaling system’s signals these days ask not are the signals honest, but how reliable are the signals.
Michael D. Beecher
Robin I. M. Dunbar
Primate societies are unusually complex compared to those of other animals, and the need to manage such complexity is the main explanation for the fact that primates have unusually large brains. Primate sociality is based on bonded relationships that underpin coalitions, which in turn are designed to buffer individuals against the social stresses of living in large, stable groups. This is reflected in a correlation between social group size and neocortex size in primates (but not other species of animals), commonly known as the social brain hypothesis, although this relationship itself is the outcome of an underlying relationship between brain size and behavioral complexity. The relationship between brain size and group size is mediated, in humans at least, by mentalizing skills. Neuropsychologically, these are all associated with the size of units within the theory of mind network (linking prefrontal cortex and temporal lobe units). In addition, primate sociality involves a dual-process mechanism whereby the endorphin system provides a psychopharmacological platform off which the cognitive component is then built. This article considers the implications of these findings for the evolution of human cognition over the course of hominin evolution.
Influential theorists of pre-adult phases of the development of the individual person (infancy, childhood, and adolescence) have articulated myriad versions of stage theories, varying in specificity, rigidity, and many other parameters. Some stage theories are concerned with capacities defined somewhat narrowly and operationally defined by behavior. Elsewhere on the spectrum, some of the most influential stage theories have purported to indicate capacities or modes of considerable generality, by positing deep, structural changes either in intellectual capacity or in terms of some other aspect of human functioning treated as fundamental to the affective and the rational life. Jean Piaget’s stage theory of intellectual (cognitive) development is the paradigm of a theory of structural changes in the capacity for logical thought. Bluntly put, Piaget’s theory takes for granted the key characteristics of the thinking of the emotionally balanced, rational adult and attempts to define the necessary steps by which that state is to be attained from the time one starts life as a baby. Sigmund Freud’s theory of psychosexual stages, especially as articulated by Karl Abraham, is the paradigm of a stage theory in which significant aspects of adult functioning are redefined, rather than taken for granted. The steps intervening from babyhood, as thereafter articulated, thereby take on an innovative character. In both cases the substantial internal consistency of the stage model, notwithstanding numerous empirical shortcomings, has generated a kind of validity. But even such qualified praise cannot now be offered to Stanley Hall’s stage theory of individual development, which seems with hindsight little more than a derivative popularization of the recapitulationary evolutionism of the latter part of the 19th century. From an historical perspective, Hall’s, Freud’s, and Piaget’s stage theories of development are all artefacts, products of the sociocultural and scientific environments of their times.
Trevor A. Harley
Research in the psychology of language has been dogged by some enduring controversies, many of which continue to divide researchers. Furthermore, language research has been riven by too many dichotomies and too many people taking too extreme a position, and progress is only likely to be made when researchers recognize that language is a complex system where simple dichotomies may not be relevant. The enduring controversies cover the width of psycholinguistics, including the work of Chomsky and the nature of language, to what extent language is innately determined and the origin of language and how it evolved. Chomsky’s work has also influenced our conceptions of the modularity of the structure of the mind and the nature of psychological processing. Advances in the sophistication of brain imaging techniques have led to debate about exactly what these techniques can tell us about the psychological processing of language. There has also been much debate about whether psychological processing occurs through explicit rules or statistical mapping, a debate driven by connectionist modeling, deep learning, and techniques for the analysis of “big data.” Another debate concerns the role of prediction in language and cognition and the related issues of the relationship between language comprehension and language production. To what extent is language processing embodied, and how does it relate to controversies about “embedded cognition”? Finally, there has been debate about the purpose and use of language.
Elissa N. Rodkey
James McCosh (b. 1811–d. 1894) was a contributor to early American psychology, writing several books on the topic of mental science. Born in Scotland, he immigrated to America in 1868 to serve as the president of the College of New Jersey (now Princeton University). There he promoted science and welcomed the new psychology that was emerging, even supporting his students to pursue psychology graduate study in Europe. McCosh saw faith and science as compatible and embraced theistic evolution as in keeping with Christian theology. McCosh’s psychological works (The Intuitions of the Mind Inductively Investigated; The Emotions; Psychology: The Cognitive Powers; and Psychology: The Motive Powers) were all relied on Scottish-Realist informed inductive methodology, used to map the functions of the mind and uncover mental laws. Although McCosh believed the new psychology had the potential for a dangerous materialism if wrongly interpreted, he thought the new physiological and laboratory research was valuable and worth pursuing. His last major work (Psychology: The Cognitive Powers) attempted to integrate recent physiological psychology research into his mental philosophy methods. McCosh has traditionally been omitted from histories of psychology, but modern scholarship has noted his absence and explored the reasons for this. Scholars generally agree that there was significant continuity between the old mental and moral philosophy and the new experimental psychology in a number of respects. The new psychologists, in attempting to professionalize and define their discipline, sought to erase their dependence on earlier forms of American psychology. Thus, it is more accurate to understand neglect of McCosh not as a sign of his irrelevance or hostility to psychology but as a historical product of the emergence of a distinct American psychology. His erasure points to the new psychologists’ uneasiness with their folk American elements and their efforts to achieve scientific status as they worked to indigenize German experimental psychology. Given his actions at Princeton, McCosh is rightly understood as a bridge builder between old and new psychology.
Diane M. Rodgers
Instinct has been one of the more contentious concepts throughout the history of psychology and social psychology. Broadly defined, instinct is considered innate, patterned behavior for living organisms that does not require learning or experience. Almost all early psychologists engaged in the study of instincts, and many attempted to classify them. One of the debates that emerged was whether there is a simple dichotomy between instinct and reason, with animals endowed with instinct for survival but only humans with the ability to rely on reason. With more influence from Darwin’s evolutionary theory, however, the idea that instincts were modifiable and a common trait for humans and animals became accepted. This also led to the idea that human instincts could be understood by examining the instincts of animals and the mental development of children. With the arrival of behaviorism, the concept of instinct began to fall out of favor altogether, and all behaviors were attributed to learning or conditioning. More recently, evolutionary psychologists have reclaimed the notion of instinct, although the understanding of this concept still varies and has an uncertain fate in the discipline.
Conscience P. Bwiza, Jyung Mean Son, and Changhan Lee
Aging is a progressive process with multiple biological processes collectively deteriorating with time, ultimately causing loss of physiological functions necessary for survival and reproduction. It is also thought to have a strong evolutionary basis, largely resulting from the lack of selection force. Here, we discuss the evolutionary aspects of aging and a selection of theories founded on a variety of biological functions that have been shown to be involved in aging in multiple model organisms, ranging from the simple yeast, worms, flies, killifish, and rodents, to non-human primates and humans. The conglomerate of distinct theories has together revolutionized aging research in the past several decades, far more than what humankind has known since the dawn of civilization. However, not one theory alone can independently explain aging and should not be interpreted out of context of the cell and organism in its entirety. That said, the 21st century has been and will be an exciting time in the field of aging, with scientific advances on health span and lifespan being made at multiple fronts of biology and medicine in an unprecedented scale.