In dynamical systems models feedforward is needed to guide planning and to process unknown and unpredictable events. Feedforward could help Theory of Event Coding (TEC) integrate control processes and could model human performance in action planning in a more flexible and powerful way.

The Theory of Event Coding (TEC) is a new framework for understanding interactions between perception and action. We are concerned that the theory is underspecified, showing that it can easily be used to make exactly opposite predictions. Precise specification of the time course of activation and binding is needed to make the theory useful for understanding the perception-action interface.

The Theory of Event Coding (TEC) provides a preliminary account of the interaction between perception and action, which is consistent with several recent findings in the area of motor control. Significant issues require integration and elaboration, however; particularly, distractor interference, automatic motor corrections, internal models of action, and neuroanatomical bases for the link between perception and action.

The Theory of Event Coding (TEC) presented in Hommel et al.'s target article provides a useful heuristic framework for stimulating research. Although the authors present TEC as providing a more integrated view of perception and action than classical information processing, TEC is restricted to the stage often called response selection and shares many features with existing theories.

We argue that the strengths of the Theory of Event Coding (TEC) can usefully be applied to a wider scope of cognitive tasks, and tested by more diverse methodologies. When allied with a theory of conceptual representation such as Barsalou's (1999a) perceptual symbol systems, and extended to data from eye-movement studies, the TEC has the potential to address the larger goals of an embodied view of cognition.

We commend the argument that perception and action are tightly coupled. We claim that the argument is not new, that uniting stimulus and response codes is not a problem for a cognitive system, only for psychologists who assume them, and that the Theory of Event Coding (TEC)'s event-codes are arbitrary and ungrounded. Affordances and information offer the common basis for perception-action (and even for event-codes).

Recent computational models of motor planning have relied heavily on anticipating the consequences of motor acts. Such anticipation is vital for dealing with the redundancy problem of motor control (i.e., the problem of selecting a particular motor solution when more than one is possible to achieve a goal). Computational approaches to motor planning support the Theory of Event Coding (TEC).

This commentary addresses three points. First, it is argued that the common coding principles, as developed in the target article, may supplement rather than replace stage views of human information processing. Second, the issue of the properties of an event code is briefly discussed. It is concluded that much remains to be specified so as to allow critical tests. Finally, the question of the limits of common coding is raised. It may be particularly relevant to direct perception and action coupling but less useful for the analysis of cognitive skills.

Although we agree with Hommel et al. that perception and action refer to one another, we disagree that they do so via a code. Gibson (1966; 1979) attempted to frame perception-action as a field phenomenon rather than as a particle phenomenon. From such a perspective, perception and action are adjoint, mutually interacting through an information field, and codes are unnecessary.

We share the authors' general approach to the study of perception and action, but rather than singling out a particular level of “late perceptual” and “early motor” processing for sensorimotor interactions, we argue that these can arise at multiple levels during action preparation and execution. Recent data on action-perception transfer are used to illustrate this perspective.

Hommel et al. propose that high-level perception and action planning share a common representational domain, which facilitates the control of intentional actions. On the surface, this point of view appears quite different from an alternative account that suggests that “action” and “perception” are functionally and neurologically dissociable processes. But it is difficult to reconcile these apparently different perspectives, because Hommel et al. do not clearly specify what they mean by “perception” and “action planning.” With respect to the visual control of action, a distinction must be made between conscious visual perception and unconscious visuomotor processing. Hommel et al. must also distinguish between the what and how aspects of action planning, that is, planning what to do versus planning how to do it.

We note two important problems in the Theory of Event Coding. First, because the representational format of features and events is unspecified, the theory is difficult to test. Second, the theory lacks a mechanism for the integration of features into an event code when the features are shared by different events. Possible ways of solving these problems are suggested.

The Theory of Event Coding deals with brief events but has implications for longer, complex events, particularly goal-directed activities. Two of the theory's central claims are consistent with or assumed by theories of complex events. However, the claim that event codes arise from the rapid activation and integration of features presents challenges for scaling up to larger events.

First, we discuss issues raised with respect to the Theory of Event Coding (TEC)'s scope, that is, its limitations and possible extensions. Then, we address the issue of specificity, that is, the widespread concern that TEC is too unspecified and, therefore, too vague in a number of important respects. Finally, we elaborate on our views about TEC's relations to other important frameworks and approaches in the field like stages models, ecological approaches, and the two-visual-pathways model.

Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The outside world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the governing laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Several lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual “filling in,” visual stability despite eye movements, change blindness, sensory substitution, and color perception.

Let us simplify the problem of “consciousness” or “visual consciousness”: Seeing is feeling. The difference between an optical transducer/effector that merely interacts with optical input, and a conscious system that sees, is that there is something it feels like for that conscious system to see, and that system feels that feeling. All talk about “internal representations” and internal or external difference registration or detection, and so on, is beside the point. The point is that what is seen is felt, not merely registered, processed, and acted upon. To explain consciousness in terms of sensorimotor action, one has to explain why and how any of that processing is felt; otherwise one is merely giving an optokinetic explanation of I/O (Input/Ouput) capacities (and of whether those capacities are actually or optimally generated by sensorimotor contingency processors, analog representations, symbolic representations, or other forms of internal structure/process), not of the fact that they are felt. Nor will it do to say “qualia are illusions.” Qualia are feelings. Am I under the illusion that I am seeing (i.e., feeling) something right now? What is the truth then? That I am not feeling, but merely acting? No, I'm afraid Descartes had it right. Certain things are not open to doubt. They either need to be explained, or passed over in silence, in favor of the unfelt correlated functions that we can explain (Harnad 1995; 2000; 2001).

Visual conscious perception could be grounded in a nonconscious sensorimotor domain. Although invisible, information can be processed up to the level of response activation. Moreover, these nonconscious processes are modified by actual intentions. This notion bridges a gap in the theoretical framework of O'Regan & Noë.

The recent interest of cognitive- and neuro-scientists in the topic of consciousness (and the dissatisfaction with the present state of knowledge) has revealed deep conceptual differences with Humanists, who have dealt with issues of consciousness for centuries. O'Regan & Noë have attempted (unsuccessfully) to bridge those differences.

Unilateral neglect stems from a relatively selective impairment of exogenous, or stimulus-related, orienting of attention. This neuropsychological evidence parallels “change blindness” experiments, in which normal individuals lack awareness of salient details in the visual scene as a consequence of their attention being exogenously attracted by a competing event, suggesting that visual consciousness requires the integrity of exogenous orienting of attention.

The sensorimotor theory of vision is the best attempt yet to explain visual consciousness without implying a Cartesian theatre. I suggest three experiments which might test the theory.