Individual differences: Case studies of rodent and primate intelligence.

Abstract

Early in the 20th century, individual differences were a central focus of psychologists. By the end of that century, studies of individual differences had become far less common, and attention to these differences played little role in the development of contemporary theory. To illustrate the important role of individual differences, here we consider variations in intelligence as a compelling example. “General intelligence” (g) has now been demonstrated in at least two distinct genera, primates (including humans, chimpanzees, bonobos, and tamarins) and rodents (mice and rats). The expression of general intelligence varies widely across individuals within a species, these variations have tremendous functional consequence, and are attributable to interactions of genes and environment. Here we provide evidence for these assertions, describe the processes that contribute to variations in general intelligence, as well as the methods that underlie the analysis of individual differences. We conclude by describing why consideration of individual differences is critical to our understanding of learning, cognition, behavior, and illustrate how attention to individual differences can contribute to more effective administration of therapeutic strategies for psychological disorders.

Zebrafish models for personalized psychiatry: Insights from individual, strain and sex differences, and modeling gene x environment interactions

“…Furthermore, individual differences in behavior of various model species are well‐documented (Tran & Gerlai, ), recognized as “personality” traits or “behavioral syndromes” (Bell, ; Sih & Bell, ; Sih, Bell, & Johnson, ; Sih, Bell, Johnson, & Ziemba, ). Animal behavioral syndromes are consistent across time and contexts (Toms & Echevarria, ), and in rodents have been reported for stress resilience (Koolhaas, ; Koolhaas, Boer, Buwalda, & Reenen, ), catecholamine and corticosterone stress responses (Sgoifo, Boer, Haller, & Koolhaas, ), aggression (de Boer, Vegt, & Koolhaas, ), cognitive abilities (Matzel & Sauce, ), locomotor activity (Friedman, Garland, & Dohm, ), sleep (Tang, Yang, & Sanford, ), and drug abuse (Spoelder et al, ). Current knowledge of behavioral syndromes in fishes (Toms & Echevarria, ) considers five main axes of animal personality: (a) shyness–boldness, (b) exploration–avoidance, (c) activity, (d) aggressiveness, and (e) sociability (Conrad, Weinersmith, Brodin, Saltz, & Sih, ).…”

The impact of environmental interventions among mouse siblings on the heritability and malleability of general cognitive ability

“…This general cognitive ability (GCA), sometimes interpreted as 'intelligence', is defined as the general capacity to learn, reason, plan and solve problems [2]. GCA can vary greatly across individuals, and studying these variations provide precious information on the genetic and environmental factors that shape this trait [3]. In addition, heritable individual differences are the necessary fuel for evolution via natural selection, and so studying the heritability of intelligence can shed light on how cognition evolved [1].…”

Validity of Cognitive Tests for Non-human Animals: Pitfalls and Prospects

“…The rationale behind selecting certain species for cognitive studies is typically a low or high degree of variation in brain size or socio-ecological factors such as breeding systems, social structures or feeding ecologies, to better understand the selective pressures driving cognitive abilities. Of particular interest for comparative psychologists are cognitive comparisons between larger-brained species (e.g., non-human primates, elephants, dolphins, and birds from the corvid and parrot families; Tomasello and Call, 1997 ; Pepperberg, 2002 ; Emery and Clayton, 2004 ; Plotnik et al, 2006 ; Byrne et al, 2009 ; Maestripieri, 2012 ; Manger, 2013 ; Güntürkün, 2014 ) and smaller-brained species (e.g., rodents, pigeons: Scarf et al, 2011 ; Matzel and Sauce, 2017 ) in order to examine the cognitive potential of large brains. More recently, an increasing number of mammalian carnivore taxa are also being studied to better understand the cognitive abilities of this large and in many aspects heterogenous order (e.g., domestic and wild dogs, hyeanas, bears, and meerkats: Townsend et al, 2012 ; Bensky et al, 2013 ; Holekamp and Benson-Amram, 2017 ; Dale et al, 2019 ; for a review see: Vonk and Leete, 2017 ).…”