The scope and limits of unconscious perception, and what it means to the function of consciousness
Integral to the action-based theory is the notion that complex perceptual integrations, such as feature binding and intersensory binding, can take place without consciousness. However, this premise regarding the power of unconsciousness rests on a sand-like ground. Although it is generally accepted that some perceptual processes can occur without consciousness, it is far from clear that binding processes such as feature binding and intersensory binding can do so as well. This is largely because of two related reasons: demonstrating a process as being unconscious requires rigorous standards; and developing optimal task conditions to reveal the power of unconsciousness is challenging.
The action-based theory considers an event unconscious when subjective experience regarding the event is lacking. Relying on subjective experience to establish unconsciousness, however, conflates consciousness with the idiosyncratic criterion for consciousness. One may, for example, report a stimulus as invisible when one can partially see it, owing to a shy, conservative personality (Bjorkman et al. Reference Bjorkman, Juslin and Winman1993). Even objective methods, which determine the level of consciousness by measuring the accuracy in forced choices, must be carefully vetted. Indeed, underestimation of consciousness has been demonstrated in recent studies reporting a phenomenon called priming of awareness (Lin & Murray Reference Lin and Murray2014a; Reference Lin and Murray2015a), which explains the underestimation of consciousness in a collection of studies on unconscious cognitive control. Therefore, it is important to distinguish just what criterion we use – subjective versus objective – when we talk about unconscious processing, and whether the method used allows us to infer unconscious processing.
Mindful of the rigorous standard required to establish unconsciousness, the task of developing optimal conditions to reveal the power of unconscious processing becomes a challenge. Although there is some evidence for unconscious perceptual binding – such as the processing of object relations (whether two objects are of the same or different shapes; Lin & Murray Reference Lin and Murray2014b) and object congruency with its context (playing with a ball vs. a watermelon in a basketball court; Mudrik et al. Reference Mudrik, Breska, Lamy and Deouell2011) – how robust and reliable these effects are remains to be tested. By all accounts, these unconscious binding effects are rather small compared with conscious effects. It is not that unconscious effects are necessarily weaker than their conscious counterparts; the reverse case has been demonstrated recently in the context of attentional cueing (Lin & Murray Reference Lin and Murray2015b). This raises the question of why unconscious binding appears to be much more limited and weaker than conscious binding.
One might lay blame on weaker sensory stimulation and less attention being allocated in the unconscious condition than in the conscious condition. Equating sensory and attentional strengths between conditions, however, may turn out to also equate our phenomenological experience in these conditions, abolishing the distinction between unconsciousness and consciousness. The very function of consciousness, then, may well be to allow salient information to bob up into the conscious field, facilitating the deployment of focal attention to furnish further operations such as sophisticated binding, thinking, and reasoning.
An unconscious binding perspective of perception and action
It is clear from the preceding discussion that we lack relevant data to evaluate the scope and limits of unconscious processing. How can we push our understanding forward? Here, the notion of binding in perception research can be naturally extended to the domain of action, because adaptive action, too, requires a solution to the binding problem. Lifting a teacup by its handle, for example, requires knowledge of spatial relations between features (the body and the handle) and the object to which they belong (the teacup). Binding, therefore, is required for both perception and action.
In the domain of perception, it has been proposed that certain types of visual binding can occur without consciousness, and such unconscious binding is more fragile than conscious binding (Lin & He Reference Lin and He2009). Given the central role of binding in perception, such an unconscious binding framework, by leveraging rich psychophysical, physiological, and computational understandings in the binding problem, could be useful for guiding us to probe the scope and limits of unconscious processing – as well as how unconscious processing interacts (binds) with conscious processing (Lin & Murray Reference Lin and Murray2013). For example, certain binding processes may be more critical than others in enabling perceptual consciousness (e.g., perceiving the teacup), and they might not be the same as those critical for enabling action consciousness (e.g., lifting the teacup). The central question then becomes just what kinds of binding require consciousness and what kinds of binding do not, and to what degree – in both perception and action. Such an unconscious binding perspective provides an informative direction along which one can delineate the scope and limits of unconscious processing, the knowledge of which is indispensable if we are to understand the nature of consciousness.
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Theories on the function of consciousness abound, with the latest from Morsella et al. (target article's passive frame theory) describing that consciousness is for adaptive voluntary action. This action-based function complements previous functions – such as social interaction and language – assigned to consciousness. While these theories share little in common, they all appear to be at odds with a simple observation: that perceptual understanding of a scene involving complex binding of the constituent parts has never been demonstrated to be free from consciousness. Consider the painting The Starry Night. While the conscious mind can easily appreciate its visual meaning – a village in the moonlight – there exists no evidence that the unconscious mind is capable of scene understanding of this sort.
This leads me to argue, in the following section, that unconscious perception may be more limited than is thought in extant theories (including the action-based theory). As a remedy, I then describe a conceptual framework that integrates perception and action based on the notion of binding, and explain how such a binding perspective, combined with rigorous methodology, can guide us to delineate the scope and limits of unconscious processing. The function of consciousness appears to be to increase the saliency of conscious contents by facilitating the deployment of focal attention – in the service of both perception and action.
The scope and limits of unconscious perception, and what it means to the function of consciousness
Integral to the action-based theory is the notion that complex perceptual integrations, such as feature binding and intersensory binding, can take place without consciousness. However, this premise regarding the power of unconsciousness rests on a sand-like ground. Although it is generally accepted that some perceptual processes can occur without consciousness, it is far from clear that binding processes such as feature binding and intersensory binding can do so as well. This is largely because of two related reasons: demonstrating a process as being unconscious requires rigorous standards; and developing optimal task conditions to reveal the power of unconsciousness is challenging.
The action-based theory considers an event unconscious when subjective experience regarding the event is lacking. Relying on subjective experience to establish unconsciousness, however, conflates consciousness with the idiosyncratic criterion for consciousness. One may, for example, report a stimulus as invisible when one can partially see it, owing to a shy, conservative personality (Bjorkman et al. Reference Bjorkman, Juslin and Winman1993). Even objective methods, which determine the level of consciousness by measuring the accuracy in forced choices, must be carefully vetted. Indeed, underestimation of consciousness has been demonstrated in recent studies reporting a phenomenon called priming of awareness (Lin & Murray Reference Lin and Murray2014a; Reference Lin and Murray2015a), which explains the underestimation of consciousness in a collection of studies on unconscious cognitive control. Therefore, it is important to distinguish just what criterion we use – subjective versus objective – when we talk about unconscious processing, and whether the method used allows us to infer unconscious processing.
Mindful of the rigorous standard required to establish unconsciousness, the task of developing optimal conditions to reveal the power of unconscious processing becomes a challenge. Although there is some evidence for unconscious perceptual binding – such as the processing of object relations (whether two objects are of the same or different shapes; Lin & Murray Reference Lin and Murray2014b) and object congruency with its context (playing with a ball vs. a watermelon in a basketball court; Mudrik et al. Reference Mudrik, Breska, Lamy and Deouell2011) – how robust and reliable these effects are remains to be tested. By all accounts, these unconscious binding effects are rather small compared with conscious effects. It is not that unconscious effects are necessarily weaker than their conscious counterparts; the reverse case has been demonstrated recently in the context of attentional cueing (Lin & Murray Reference Lin and Murray2015b). This raises the question of why unconscious binding appears to be much more limited and weaker than conscious binding.
One might lay blame on weaker sensory stimulation and less attention being allocated in the unconscious condition than in the conscious condition. Equating sensory and attentional strengths between conditions, however, may turn out to also equate our phenomenological experience in these conditions, abolishing the distinction between unconsciousness and consciousness. The very function of consciousness, then, may well be to allow salient information to bob up into the conscious field, facilitating the deployment of focal attention to furnish further operations such as sophisticated binding, thinking, and reasoning.
An unconscious binding perspective of perception and action
It is clear from the preceding discussion that we lack relevant data to evaluate the scope and limits of unconscious processing. How can we push our understanding forward? Here, the notion of binding in perception research can be naturally extended to the domain of action, because adaptive action, too, requires a solution to the binding problem. Lifting a teacup by its handle, for example, requires knowledge of spatial relations between features (the body and the handle) and the object to which they belong (the teacup). Binding, therefore, is required for both perception and action.
In the domain of perception, it has been proposed that certain types of visual binding can occur without consciousness, and such unconscious binding is more fragile than conscious binding (Lin & He Reference Lin and He2009). Given the central role of binding in perception, such an unconscious binding framework, by leveraging rich psychophysical, physiological, and computational understandings in the binding problem, could be useful for guiding us to probe the scope and limits of unconscious processing – as well as how unconscious processing interacts (binds) with conscious processing (Lin & Murray Reference Lin and Murray2013). For example, certain binding processes may be more critical than others in enabling perceptual consciousness (e.g., perceiving the teacup), and they might not be the same as those critical for enabling action consciousness (e.g., lifting the teacup). The central question then becomes just what kinds of binding require consciousness and what kinds of binding do not, and to what degree – in both perception and action. Such an unconscious binding perspective provides an informative direction along which one can delineate the scope and limits of unconscious processing, the knowledge of which is indispensable if we are to understand the nature of consciousness.