The cognitive unconscious : a historical and critical introduction

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In historical terms, we begin by pointing out that, contrary to popular belief, the concept of the unconscious did not originate with Freud and his contemporaries (Gauchet, 1992). What's more, many aspects of Freud's theory of the unconscious are not echoed in contemporary research. Such is the case, for example, with the hypothesis of an unconscious with its own intentions and desires, often of infantile origin, and structured by mechanisms of repression and censorship. To avoid confusion with Freudian theoretical constructs, cognitive psychology therefore often prefers the more neutral terms of non-conscious or cognitive unconscious to the term unconscious (Kihlstrom, 1987).

Many philosophers, from the classical era onwards, have emphasized the considerable part played by the non-conscious in our physical and mental activities. Descartes, in his Traité de l'Homme, draws attention to the "movements we make without our will contributing to them", which "depend only on the conformation of our limbs and the lecture that the spirits (...) naturally follow in the brain". Spinoza asserts that the feeling of free will emerges from the fact that "men are conscious of their desires and ignorant of the causes that determine them". Malebranche, Diderot, Maine du Biran and many others also stressed the non-conscious foundations of our motivations and automatisms.

However, it wasn't until the ^19th century that the first experimental data from neurology emerged in support of non-conscious brain operations. Two theoretical constructs played an essential role here: the concept of the reflex arc, which provided proof of the absence of voluntary control over some of our movements (Hall, 1832); and the Jacksonian principle of a functional hierarchy of the nervous system, the lowest levels of which are occupied by automatic functions controlled by the spinal cord and brain stem. In psychology, von Helmholtz discovered that visual perception was based on elaborate operations that could almost be described as logical or rational, but which nevertheless remained inaccessible to introspection - he called them "unconscious inferences". Théodule Ribot enunciates the first laws of memory and amnesia, and demonstrates the existence of an unconscious memory of know-how. Alongside Charcot and before Freud, Pierre Janet conducted the first experimental studies of somnambulism, hypnosis, hysteria, automatic writing and mental "possession" at the Salpêtrière and Collège de France. Claiming to have coined the term "subconscious", he noted in L'automatisme psychologique (1889) the extent of human activities that fall within the scope of automatism, either total (extending to the entire subject) or partial (part of the personality is excluded from consciousness and pursues objectives of its own). In sociology, Gabriel Tarde published Les Lois de l'imitation (1890), in which he developed the idea that an elaborate mechanism of non-conscious imitation governs crowd psychology and the formation of human societies. In short, the concept of non-conscious operation was already familiar to psychologists by the end of the nineteenth century.

The neuropsychologists of the late ^nineteenth and early ^twentieth centuries were responsible for the discovery of three major brain pathologies in which the non-conscious is clearly involved. Firstly, retrograde amnesia: in certain patients who can no longer consciously recall events experienced hours or minutes earlier, Korsakoff, Claparède and, more recently, the Canadian psychologist Brenda Milner demonstrated the persistence of an implicit capacity to learn new skills: memorizing an emotional experience, the floor plan of a house, the solution to a maze... Blind vision: as early as 1917, Riddoch, then Ernst Pöppel, and finally Larry Weiskrantz studied several patients with lesions of the primary visual area, which classical neurology stipulates abolish all conscious vision (cortical blindness). They demonstrate that, in reality, the patient still possesses, without being aware of it, a vision of movement and an ability to point or direct the eyes towards a target - residual functions that would involve non-conscious circuits of the superior colliculus, pulvinar and amygdala.

A third category of patients presents spatial hemineglect, characterized by the inability to perceive and pay attention to certain stimuli presented in the left half of the visual field (or, in some cases, on the left side of the object under examination). Edoardo Bisiach, John Marshall and many others demonstrated that the "neglected" part of the image, although not consciously reported, is analyzed at a high cognitive level: it activates visual and semantic pathways, and influences cognitive and motor decisions.

In the 1950s, a final scientific revolution legitimized the question of information processing without consciousness. Information theory (Shannon) and the discovery of universal computational mechanisms (Wiener, Turing, von Neumann) had a profound influence on the then nascent field of cognitive psychology. The metaphor of the computer suggests a purely computational or algorithmic description of mental operations. In this context, the non-conscious processing of information no longer poses any conceptual difficulty, since computers operate without consciousness. On the contrary, the very nature and existence of consciousness became the subject of controversy, to the extent that the scientific study of consciousness remained on the bangs of cognitive science for several decades. It only came back to the fore in the 1980s-1990s, with the emergence of experimental paradigms skilfully controlled to present information in a non-conscious way.