Nijhawan argues that delays inherent in the transmission of information introduce error into perceptual and motor processes. Such delays are primarily a consequence of the time required to transmit information from the world to the central nervous system (perception) and from the central nervous system to the world (action). These delays create error between the actual state of the world and the state of the world perceived (and acted on) by the nervous system. As a result, delay compensation mechanisms are required to correct this error, and such mechanisms are a pervasive feature of the nervous system (particularly the visual and motor planning systems). I propose that delay compensation mechanisms are necessary only if perception and action are (mis)characterized (a) as fundamentally separate linear and mechanistic processes, and (b) as processes that (primarily) occur with reference to the immediate present. From the perspective of ecological psychology (J. Gibson Reference Gibson1979; Reed Reference Reed1996), both (a) and (b) characterizations are rejected. Thus, from this perspective, the proposed delays do not exist, and delay compensation mechanisms are unnecessary.
Perception-action as reciprocal and continuous
The delays described by Nijhawan reflect those that are inherent in the receiving and sending of information. As a result, such delays (and the need for delay compensation mechanisms) are dependent upon characterizations of perception and action as processes in which information is received and sent, respectively. That is, they are dependent upon a characterization of perception and action as information processing. From such a perspective, perception and action are inherently separate processes in which information is transmitted in a sequence of linear and mechanistic steps. Therefore, perception and action are subject to the time delays inherent to such processes.
From the perspective of ecological psychology, far from being separate, linear, and mechanistic, perception and action are reciprocal and continuous. Perception and action are circularly causal in that perceiving refers to acting, and acting refers to perceiving (Shaw & Wagman Reference Shaw and Wagman2001). It is inappropriate to label perception as “input” and action as “output,” because perception and action are multidirectional and mutually constraining. Perception is action, in that exploratory behaviors (e.g., head movements or manipulation of a handheld object) reveal properties of the world that would otherwise remain hidden. To paraphrase James Gibson (Reference Gibson1979, p. 223), “As much as we must perceive in order to move, we must also move in order to perceive.
To ecological psychologists, perception-action is a continuous event with no clear beginning or end. The relationship between perception and action is more like the continuum that exists between the sides of a Möbius band than like the relationships among the parts of a clock (Turvey Reference Turvey, Jirsa and Kelso2004). For this reason, ecological psychologists refer to the relationship between perceiving and acting as “perception-action” much as physicists refer to the relationship between space and time as “space-time.” If perception-action is characterized in this way, then delays between perception and action are impossible because perception-action is a continuous event (Turvey Reference Turvey, Jirsa and Kelso2004). No transmission of information is necessary (or even possible), and delays between perception and action do not (and cannot) occur. Therefore, delay compensation mechanisms are unnecessary.
Perception-action as a prospective act
According to Nijhawan, the delays created by the transmission of information in the nervous system are problematic because they produce an error between the “instantaneous registered state” of the world and the actual state of the world. As a result, perception necessarily “lags behind” the world and must be “brought up to speed” by the pervasive delay compensation mechanisms in the nervous system. Such delays seem particularly problematic in situations in which a behavior requires prediction of a future event (such as a batsman attempting to hit a ball thrown by a bowler). However, in addition to being dependent on a characterization of perception as information processing, such delays (and the need for delay compensation mechanisms) are also dependent upon a characterization of perception and action as processes that (primarily) occur with reference to the immediate (i.e., instantaneous) present.
From the perspective of ecological psychology, perception-action primarily occurs with reference to the (impending) future (Wagman & Malek, in press). In order to successfully achieve a behavioral goal (e.g., reaching for a cup of coffee or hitting a thrown ball), perceiver-actors must be able to perceive whether that (future) behavior is possible, and (if so) they must be able to perceive how to control their (future) movements such that this possibility is realized (Shaw & Turvey Reference Shaw and Turvey1999). Thus, perception-action is inherently a prospective act (Turvey Reference Turvey1992). If perception-action is inherently prospective, there is no need for the nervous system to bring the perceiver-actor “up to speed” because perception-action places awareness “ahead of the world.”
The prospectivity of perception-action is considered by some to be one of the fundamental hallmarks of a psychological being (E. Gibson Reference Gibson1994). From the perspective of ecological psychology, the stimulation variables that support such prospectivity are not the static and isolated variables of standard physics (so-called “lower-order” stimulation variables) but, rather, are the dynamic and relational variables of an ecological physics (so-called “higher order” stimulation variables) (Turvey & Shaw Reference Turvey and Shaw1999). For example, a handheld object's resistance to rotational acceleration in different directions not only informs a perceiver about whether that object can be used to achieve a particular goal (e.g., striking another object) but also about how that object should be used to do so (Wagman & Carello Reference Wagman and Carello2001; Reference Wagman and Carello2003). If perception-action is characterized as a prospective act, then there is no need for delay compensation mechanisms in perception-action because higher-order relational variables are sufficient to specify impending states of affairs without the need for mediating processes.
Delays that are inherent in the sending and receiving of information create an explanatory gap in a scientific understanding of perception and action. However, rather than fill that gap with specialized delay compensation mechanisms, I propose that perception and action be (re)characterized in a way in which such delays are an impossibility and the explanatory gap dissolves. The ecological approach to perception-action provides such a (re)characterization.
