The Evolution of Symbolic Thought: At the Intersection of Schizophrenia Psychopathology, Ethnoarchaeology, and Neuroscience

Culture, Medicine, and Psychiatry https://doi.org/10.1007/s11013-024-09873-5 PERSPECTIVES The Evolution of Symbolic Thought: At the Intersection of Schizophrenia Psychopathology, Ethnoarchaeology, and Neuroscience Matteo Tonna1,2 Accepted: 29 June 2024 © The Author(s) 2024 Abstract The human capacity for symbolic representation arises, evolutionarily and developmentally, from the exploitation of a widespread sensorimotor network, along a fundamental continuity between embodied and symbolic modes of experience. In this regard, the fine balancing between constrained sensorimotor connections (responsible for self-embodiment processing) and more untethered neural associations (responsible for abstract and symbolic processing) is context dependent and plastically neuromodulated, thus intersubjectively constructed within a specific socio-cultural milieu. Instead, in the schizophrenia spectrum this system falls off catastrophically, due to an unbalance toward too unconstrained sensorimotor connectivity, leading to a profound distortion of self/world relation with a symbolic activity detached from its embodied ground. For this very reason, however, schizophrenia psychopathology may contribute to unveil, in a distorted or magnified way, ubiquitous structural features of human symbolic activity, beneath the various, historically determined cultural systems. In this respect, a comparative approach, linking psychopathology and ethnoarchaeology, allows highlight the following invariant formal characteristics of symbolic processing: (1) Emergence of salient perceptive fragments, which stand out from the perceptual field. (2) Spreading of a multiplicity of new significances with suspension of common-sense meaning. (3) Dynamic and passive character through which meaning proliferation is experienced. This study emphasizes the importance of fine-grained psychopathology to elucidate, within a cross-disciplinary framework, the evolutionarily and developmental pathways that shape the basic structures of human symbolization. Keywords Culture · Development · Embodiment · Language · Self · Sensorimotor * Matteo Tonna 1 Department of Medicine and Surgery, Psychiatric Unit, University of Parma, Ospedale Maggiore, Padiglione Braga, Viale A. Gramsci 14, 43126 Parma, Italy 2 Department of Mental Health, Local Health Service, Parma, Italy 13 Vol.:(0123456789) Culture, Medicine, and Psychiatry Introduction The emergence of symbolic thought represents a tipping-point in the evolution of human mind, marking the split from our ancestors (Bentley & O’Brien, 2012). Growing evidence suggests that this uniquely human capacity, instead of being “encapsulated” in newly acquired cognitive modules, is actually firmly grounded in our bodily enactment, along a continuum from embodied to symbolic mode of experience (Borghi et al., 2022). This continuity lies in fact on the high flexibility of sensorimotor networks, which are plastically re-adapted from rigid neuro-chemical constraints (for concrete representations) to relatively unconstrained connections (to convey more abstract and symbolic concepts) (Mazzuca et al., 2021). In particular, the disproportionate expansion of the cortical mantle during human evolution leads to neural patterning partly freed from chemical signaling gradients, opening up more flexible and dynamic neural configurations, which are more developmentally constructed than phylogenetically fixed (Buckner & Krienen, 2013). The increasing degree of neural “relaxation” paved the way for the extensive exploitation of sensorimotor grounding for symbolic activity, driven by complex bio-cultural feedbacks within specific culturally constructed niches (Stout & Hecht, 2017; Tattersall, 2016). The importance of cultural developmental forces in shaping human symbolism has been particularly emphasized in ethnoarchaeological accounts. Ethnoarchaeology is an interdisciplinary approach aimed at investigating the relationship of material culture to culture as a whole, both in the living context and as it enters the archaeological record (Nicholas & Kramer, 2001). Under this perspective in fact, human symbolic activity presents a shared, constructed, inter-dependent character, unfolding within a subject–object circular relationship in a given socio-cultural milieu (Hodder, 2011; Malafouris, 2019). From a psychopathological perspective, schizophrenia is the clinical condition that most dramatically questions the human attitude to symbolization. Patients with schizophrenia in fact typically appear immersed in empty symbolic constructions, while being detached from the common-sense world of shared, everyday meanings (de Vries et al., 2013; Sass, 1992a, b). Remarkably, schizophrenia is a uniquely human condition (Insel, 2010) and, like symbolic activity, it has been specifically linked to the evolution of language (DeLisi, 2021). Therefore, the present contribution, adopting a cross-disciplinary approach, sought to (1) trace the evolutionary scaffolding of human symbolic activity; (2) compare modes of symbolic representation as manifested in ethnoarchaeological accounts and as reported in schizophrenia psychopathology, with the aim of investigating possible invariant formal features underlying symbolic thought, based on common evolutionary pathways. 13 Culture, Medicine, and Psychiatry The Inter‑dependent Nature of Human Symbolic Evolution According to an embodied, situated approach, the basic structures of subjectivity develop from the very beginning within and through a diffuse network of other subjects and worldly objects, mediated by bodily enactment (Gallagher, 2017; Gallese & Ferri, 2014; Laland, 2017). In this connection, also our immediate and meaningful attachment to the world (the common sense) spreads from a dynamic engagement with things and bodily manipulation (Chemero, 2019; Park & Baxter, 2022). On the other hand, things, instead of being inert perceptual objects of a detached mind, actually represent a meaningful background of culturally transmitted practices, uses, and affordances, which actively contribute to shape our grasp with the world. Therefore, meaning attribution processing is shaped (both evolutionarily and developmentally) within a co-constitutive intertwining of brains, bodies, and things, in which “things” (in the broader sense of material forms, socio-cultural assemblages and techniques) actively and dynamically bring forth and constrain human possibilities for action and thinking (Hodder, 2011; Malafouris, 2019) (shown in Fig. 1). It is such an embodied and socio-cultural unity of the self and worldly things to color our practical immersion in the life-world with a feeling of habituality or familiarity (Fuchs & Schlimme, 2009). The net of recursive relationships between our mind and material culture is malleable, due to the high plasticity of both brain and culture and thus context dependent, being irreducibly situated in space and time (Malafouris, 2015). This is (...truncated)