Darwin’s Mistake: Explaining the Discontinuity between Human and Nonhuman Minds

Department of Psychology, University of California-Los Angeles, Los Angeles, CA 90095, USA.
Behavioral and Brain Sciences (Impact Factor: 20.77). 05/2008; 31(2):109-30; discussion 130-178. DOI: 10.1017/S0140525X08003543
Source: PubMed


Over the last quarter century, the dominant tendency in comparative cognitive psychology has been to emphasize the similarities between human and nonhuman minds and to downplay the differences as "one of degree and not of kind" (Darwin 1871). In the present target article, we argue that Darwin was mistaken: the profound biological continuity between human and nonhuman animals masks an equally profound discontinuity between human and nonhuman minds. To wit, there is a significant discontinuity in the degree to which human and nonhuman animals are able to approximate the higher-order, systematic, relational capabilities of a physical symbol system (PSS) (Newell 1980). We show that this symbolic-relational discontinuity pervades nearly every domain of cognition and runs much deeper than even the spectacular scaffolding provided by language or culture alone can explain. We propose a representational-level specification as to where human and nonhuman animals' abilities to approximate a PSS are similar and where they differ. We conclude by suggesting that recent symbolic-connectionist models of cognition shed new light on the mechanisms that underlie the gap between human and nonhuman minds.

Download full-text


Available from: Keith J Holyoak,
  • Source
    • "First, we review prior work in this area from a range of sources and then describe our current research focused on studying the relationship between language and reasoning in individuals with varying degrees of language impairment. Evidence from a number of animal studies clearly demonstrate remarkable reasoning and problem-solving abilities in nonhuman species (Blaisdell et al., 2006; Taylor et al., 2009; Smirnova et al., 2015), but it is argued that such abilities have reached a higher level in humans (Premack, 1983, 2007; O'Brien and Opie, 2002; Penn et al., 2008). Since abstract, symbolic language reaches its apex in humans as well, it has been suggested that these abilities are causally related, that is, our language system facilitates logical reasoning in some way (Sokolov, 1968/1972; Premack, 1983; Carruthers, 2002; O'Brien and Opie, 2002; Bermudez, 2003; Gentner, 2003; Kuczaj and Hendry, 2003; Goel and Dolan, 2004). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The precise nature of the relationship between language and thought is an intriguing and challenging area of inquiry for scientists across many disciplines. In the realm of neuropsychology, research has investigated the interdependence of language and thought by testing individuals with compromised language abilities and observing whether performance in other cognitive domains is diminished. One group of such individuals is patients with aphasia who have an impairment in speech and language arising from a brain injury, such as a stroke. Our previous research has shown that the degree of language impairment in these individuals is strongly associated with the degree of impairment on complex reasoning tasks, such as the Wisconsin Card Sorting Task (WCST) and Raven's Matrices. In the current study, we present new data from a large group of individuals with aphasia that show a dissociation in performance between putatively non-verbal tasks on the Wechsler Adult Intelligence Scale (WAIS) that require differing degrees of reasoning (Picture Completion vs. Picture Arrangement tasks). We also present an update and replication of our previous findings with the WCST showing that individuals with the most profound core language deficits (i.e., impaired comprehension and disordered language output) are particularly impaired on problem-solving tasks. In the second part of the paper, we present findings from a neurologically intact individual known as " Chelsea " who was not exposed to language due to an unaddressed hearing loss that was present since birth. At the age of 32, she was fitted with hearing aids and exposed to spoken and signed language for the first time, but she was only able to acquire a limited language capacity. Chelsea was tested on a series of standardized neuropsychological measures, including reasoning and problem-solving tasks. She was able to perform well on a number of visuospatial tasks but was disproportionately impaired on tasks that required reasoning, such as Raven's Matrices and the WAIS Picture Arrangement task. Together, these findings suggest that language supports complex reasoning, possibly due to the facilitative role of verbal working memory and inner speech in higher mental processes.
    Frontiers in Psychology 10/2015; 6. DOI:10.3389/fpsyg.2015.01523 · 2.80 Impact Factor
    • "However, those claims have been heavily disputed on the ground that the paradigms failed to include sufficiently abstract generalization items and that the behavior was in fact driven by simpler non-recursive representation of transition probabilities and transition patterns (Beckers et al., 2012; ten Cate and Okanoya, 2012; Fitch and Friederici, 2012; van Heijningen et al., 2009). Instead, a variety of behaviors such as sequence learning, tool use, music, or mathematics suggest that the capacity to acquire and manipulate embedded tree structures may be a uniquely human feat (Fitch, 2014; Hauser et al., 2002; Penn et al., 2008). "
    [Show abstract] [Hide abstract]
    ABSTRACT: A sequence of images, sounds, or words can be stored at several levels of detail, from specific items and their timing to abstract structure. We propose a taxonomy of five distinct cerebral mechanisms for sequence coding: transitions and timing knowledge, chunking, ordinal knowledge, algebraic patterns, and nested tree structures. In each case, we review the available experimental paradigms and list the behavioral and neural signatures of the systems involved. Tree structures require a specific recursive neural code, as yet unidentified by electrophysiology, possibly unique to humans, and which may explain the singularity of human language and cognition.
    Neuron 10/2015; 88(1):2-19. DOI:10.1016/j.neuron.2015.09.019 · 15.05 Impact Factor
  • Source
    • "Studies of comparative cognition are therefore clinically relevant for autism spectrum disorder (ASD), which is characterized by deficits in both human-unique and evolutionarily conserved aspects of social cognition. For example, theory of mind (ToM), is a largely (if not uniquely) human cognitive function (Call and Tomasello 2008; Penn et al. 2008) and is impaired in ASD (Boucher 2012). Nonetheless, individuals with ASD also show fundamental deficits in social reasoning abilities which are not uniquely human, and which are shared with many highly social nonhuman species. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Comparative studies of social responsiveness, a core impairment in autism spectrum disorder (ASD), will enhance our understanding of typical and atypical social behavior. We previously reported a quantitative, cross-species (human-chimpanzee) social responsiveness measure, which included the development of the Chimpanzee Social Responsiveness Scale (CSRS). Here, we augment our prior CSRS sample with 25 zoo chimpanzees at three sites: combined N = 54. The CSRS demonstrated strong interrater reliability, and low-ranked chimpanzees, on average, displayed higher CSRS scores. The CSRS continues to discriminate variation in chimpanzee social responsiveness, and the association of higher scores with lower chimpanzee social standing has implications for the relationship between autistic traits and human social status. Continued comparative investigations of social responsiveness will enhance our understanding of underlying impairments in ASD, improve early diagnosis, and inform future therapies.
    Journal of Autism and Developmental Disorders 05/2015; 45(5):1483-1488. DOI:10.1007/s10803-014-2273-9 · 3.34 Impact Factor
Show more