Ezequiel Morsella

Historically, consciousness has been linked to the highest of intellectual functions. For example, investigators have proposed that the primary function of consciousness pertains to language, “theory of mind,” the formation of the self, semantic processing, the meaningful interpretation of situations, and simulations of behavior and perception. This chapter determines what consciousness is for by focusing on the primary, basic role that consciousness contributes to action production. It approaches this question from a nontraditional perspective—by working backward from overt voluntary action to the underlying central processes. This approach reveals that the primary function of consciousness (to yield adaptive skeletomotor action by instantiating a unique form of integration, or “binding”) is more basic-level than what has been proposed. In addition, it reveals that “volition” and the skeletal muscle output system are intimately related to this primary function of consciousness.

The basic nuts and bolts underlying human behavior remain mysterious from a scientific point of view. Everyday acts -- naming an object, suppressing the urge to say something, or grabbing a waiter's attention with a "cappuccino, please" -- remain difficult to understand from a mechanistic standpoint. Despite these challenges, research has begun to illuminate, not only the basic processes underlying human action production, but the role of conscious processing in the control of behavior. This Research Topic, "Consciousness and the Control of Action," is devoted to surveying and synthesizing these developments from disparate fields of study.

In 1959, Neal Miller made the bold claim that the Stimulus–Response, Behaviorist models of that era were describing the way in which stimuli lead to the entry of contents into consciousness (“entry,” for short). Today, researchers have begun to investigate the link between external stimuli and involuntary entry, using paradigms such as the reflexive imagery task (RIT), the focus of our review. The RIT has revealed that stimuli can elicit insuppressible entry of high-level cognitions. Knowledge of the boundary conditions of the RIT effect illuminates the limitations of involuntary processes and the role of consciousness in the regulation of behavior. We review the boundary conditions of this paradigm as well as its systematic effects. Systematic effects are unlikely to be due to experimental demand. While reviewing each effect, we consider its theoretical implications. In addition, throughout our review, we discuss future directions for the study of insuppressible entry using the RIT. Last, we discuss a theoretical development (passive frame theory) that stems from the RIT and illuminates how involuntary entry and encapsulation, though at times disadvantageous for the actor, are essential for adaptiveaction selectionduring the course of ontogeny.

The Reflexive Imagery Task (RIT) reveals that the activation of sets can result in involuntary cognitions that are triggered by external stimuli. In the basic RIT, subjects are presented with an image of an object (e.g., CAT) and instructed to not think of the name of the object. Involuntary subvocalizations of the name (the RIT effect) arise on roughly 80% of the trials. We conducted an electroencephalography (EEG) study to explore the neural correlates of the RIT effect. Subjects were presented with one object at a time in one condition and two objects simultaneously in another condition. Five regions were defined by electrode sites: frontal (F3–F4), parietal (P3–P4), temporal (T3–T4), right hemisphere (F4–P4), and left hemisphere (F3–P3). We focused on the alpha (8–13 Hz), beta (13–30 Hz), delta (0.01–4 Hz), and theta (4–8 Hz) frequencies.

High-level cognitions can enter consciousness through the activation of certain action sets and the presentation of external stimuli (“set-based entry,” for short). Set-based entry arises in a manner that is involuntary and systematic. In the Reflexive Imagery Task, for example, subjects are presented with visual objects and instructed to not think of the names of the objects. Involuntary subvocalizations arise on roughly 80% of the trials. We examined whether or not set-based entry can also occur in the case of involuntary counting. Subjects in Experiment 1A were instructed to not count the number of objects presented in an array. Involuntary counting arose on a high proportion of the trials (a mean proportion of ∼0.90) for stimulus arrays having 2–5 objects, and such counting arose less frequently across trials when the array consisted of 6–10 objects (a mean proportion of ∼0.21). The data from Experiment 1B revealed that, when people choose to perform Set X, they also experience thoughts about an unselected Set (Set Y ). Subjects were trained on one set (e.g., to “color name”) and then, when presented with stimuli, were given the choice to perform the trained set or a novel set. Consistent with theories proposing that the conscious contents represent several potential action plans, subjects were equally likely to experience set-related imagery or set-unrelated imagery. Our findings regarding set-based entry are relevant to many subfields of psychology and neuroscience (e.g., the study of high-level mental processes, attention, imagery, and action control).

Investigations of human action have led to the conclusion that much action production can occur unconsciously. Behaviors such as reflexes and automatisms in neurological conditions reveal that action production can be mediated unconsciously. Less obvious, however, are the unconscious mechanisms associated with everyday voluntary actions. Voluntary action is a complex form of action that involves both unconscious and conscious component processes. This chapter reviews the unconscious components of voluntary action and then examines how these components interact with consciousness. The analysis includes treatments of Skinner’s influential “three-term contingency” and the phenomenon of effortless control. The chapter discusses the unresolved issues and paradoxes that are encountered when investigating action from a reductionistic standpoint in which there is no homunculus-like agent involved in voluntary action.

The contents of our conscious mind can seem unpredictable, whimsical, and free from external control. When instructed to attend to a stimulus in a work setting, for example, one might find oneself thinking about household chores. Conscious content thus appears different in nature from reflex action. Under the appropriate conditions, reflexes occur predictably, reliably, and via external control. Despite these intuitions, theorists have proposed that, under certain conditions, conscious content resembles reflexes and arises reliably via external control. We introduce the Reflexive Imagery Task, a paradigm in which, as a function of external control, conscious content is triggered reliably and unintentionally: When instructed to not subvocalize the name of a stimulus object, participants reliably failed to suppress the set-related imagery. This stimulus-elicited content is considered ‘high-level’ content and, in terms of stages of processing, occurs late in the processing stream. We discuss the implications of this paradigm for consciousness research.

Although it is well accepted that working memory is intimately related to consciousness, little research has illuminated the liaison between the two phenomena. To investigate this under-explored nexus, we used an imagery monitoring task to investigate the subjective aspects of WM performance. Specifically, in two experiments, we examined the effects on consciousness of holding in mind information having a low versus high memory load, and holding memoranda in mind during the presentation of distractors . Higher rates of rehearsal occurred in the high load and distractor conditions than in comparable control conditions. Examination of the temporal properties of the rehearsal-based imagery revealed that, across subjects, imagery events occurred evenly throughout the delay. We hope that future variants of this new imagery monitoring task will reveal additional insights about WM, consciousness, and action control

The conscious field includes not only representations about external stimuli (e.g., percepts), but also conscious contents associated with internal states, such as action-related intentions (e.g., urges). Although understudied, the latter may provide unique insights into the nature of consciousness. To illuminate these phenomena, in a new experimental paradigm [ Reflexive Imagery Task (RIT)], participants were instructed to not subvocalize the names of visually-presented objects. Each object was presented for 10 s on a screen. Participants indicated whenever they involuntarily subvocalized the object name. Research has revealed that it is difficult to suppress such subvocalizations, which occur on over 80% of the trials. Can the effect survive if one intentionally generates a competing (internally-generated) conscious content? If so, this would suggest that intentional and unintentional contents can co-exist simultaneously in consciousness in interesting ways. To investigate this possibility, in one condition, participants were instructed to reiteratively subvocalize a speech sound (“da, da, da”) throughout the trial. This internally generated content is self-generated and intentional. Involuntary subvocalizations of object names still arose on over 80% of the trials. One could hypothesize that subvocalizations occurred because of the pauses between the intended speech sounds, but this is inconsistent with the observation that comparable results arose even when participants subvocalized a continuous, unbroken hum (“daaa….”) throughout the trial. Regarding inter-content interactions, the continuous hum and object name seem to co-exist simultaneously in consciousness. This intriguing datum requires further investigation. We discuss the implications of this new paradigm for the study of internally-generated conscious contents.