Following Paillard (Reference Paillard, Gantchev, Mori and Massion1999) and consistent with the conceptualization of visual pathways for perception and action (e.g., Milner & Goodale Reference Milner and Goodale1995), Dijkerman & de Haan (D&dH) claim that the perceptual somatosensory pathway informs a body image that is conscious, but that information in the action pathway is interpreted within a body schema that is not consciously accessible. Paillard described the body image as an internal representation of body features. The body schema, on the other hand, describes the position of body parts relative to one another as represented by an internal sensorimotor body map. These definitions would suggest that the position of one limb, relative to another, is not normally represented in consciousness, presuming that vision of the limbs is unavailable.

D&dH present ample evidence from patients (e.g., see Rossetti et al. Reference Rossetti, Rode and Boisson1995b; Reference Rossetti, Rode, Boisson, de Gelder, De Haan and Heywood2001) and healthy subjects (e.g., see Westwood & Goodale Reference Westwood and Goodale2003) to support their claims. However, a growing literature within the movement sciences suggests that we can become acutely aware of the position of our limbs and their movement relative to each other (e.g., Beilock & Carr Reference Beilock and Carr2001; Gray Reference Gray2004; Masters & Maxwell Reference Masters, Maxwell, Williams and Hodges2004; Wulf et al. Reference Wulf, McNevin and Shea2001), particularly when required to perform under adverse psychological conditions (e.g., competitive pressure; Masters Reference Masters1992) or in degraded sensory environments (e.g., Maxwell et al. Reference Maxwell, Masters and Eves2003). Maxwell et al. (Reference Maxwell, Masters and Eves2003) demonstrated that withholding visual feedback about the outcome of a golf-putting task caused subjects to focus their attention on the mechanics of their movements. Also, Gray (Reference Gray2004) found that expert baseball players are acutely aware of their batting action, particularly when playing poorly – an observation supported by Maxwell and colleagues' contention that performance errors tend to increase conscious awareness of movement parameters (Maxwell et al. Reference Maxwell, Masters, Kerr and Weedon2001; Poolton et al. Reference Poolton, Masters and Maxwell2005; in press). Masters et al. (Reference Masters, MacMahon and Pall2004) also found that Parkinson's patients report being more aware of their movements than healthy age-matched controls, which suggests conscious monitoring of their actions.

Furthermore, it is traditionally recognized that as expertise is acquired, athletes become increasingly reliant on the availability of proprioceptive information and less reliant on visual information to control their movements and posture (Bardy & Laurent Reference Bardy and Laurent1998; Fleishman & Rich Reference Fleishman and Rich1963; Robertson et al. Reference Robertson, Collins, Elliott and Starkes1994; Robertson & Elliot Reference Robertson and Elliott1996). Athletes, particularly those with aesthetic aspects to their sport, also often practice with their eyes closed, presumably in an attempt to enhance awareness of proprioceptive feedback generated by their movements.

More controversial is evidence that newborn infants are aware of their movements. Rochat and Morgan (Reference Rochat and Morgan1995) simultaneously presented 3-month-old infants with two online video images of their own kicking legs. The infants looked longer and generated more leg activity while looking at the video image displaying their leg movements in a direction different than they were producing (i.e., the legs were displayed with a left-right inversion). Thus, even preverbal infants may be aware of how they move body parts relative to one another.

These observations suggest that both the body image and the body schema may be consciously accessible in some circumstances or that the information normally contained within the body schema is somehow represented by the body image. However, Masters and colleagues also contend that conscious access to this information may be detrimental to the production of fluent, accurate movements (e.g., see Baumeister Reference Baumeister1984; Masters Reference Masters1992; Masters & Maxwell Reference Masters, Maxwell, Williams and Hodges2004). Masters and Maxwell (Reference Masters, Maxwell, Williams and Hodges2004) argue that movement control should remain implicit (automatic and unconscious), rather than explicit (controlled and conscious), if optimal performance is desired. They reason that conscious processing of movement parameters places a heavy load on working memory resources (Baddeley Reference Baddeley1986). When working memory must process secondary information (e.g., tactical decisions; Poolton et al. Reference Poolton, Masters and Maxwell2006), movements are susceptible to disruption. Implicit or unconscious processing does not tax working memory and is, therefore, less susceptible to disruption from secondary tasks. Hence, Masters and Maxwell suggest that the learner should not attempt to focus on the mechanics of their movements.

The detrimental effects of focusing internally, on the mechanics of movement, have also been repeatedly demonstrated by Wulf and colleagues (for a review, see Wulf & Prinz Reference Wulf and Prinz2001). They argue that focusing internally constrains movement parameters, interfering with their normally automatic execution (McNevin et al. Reference McNevin, Shea and Wulf2003). In contrast, focusing externally, on the outcome of movement, has been shown to maximize performance and promote automaticity. It could be argued that focusing internally promotes conscious processing of the body schema.

Masters and Maxwell (Reference Masters, Maxwell, Williams and Hodges2004) have couched their implicit motor learning theory within an evolutionary context, claiming that implicit motor processes are more stable than explicit processes because the former evolved first (Reber Reference Reber1992). It is plausible that the neurological structures that support the action pathway evolved before structures supporting the perceptual pathway. Evolutionarily older processes tend to be less susceptible to disruption from psychological stress, disorders, and dysfunctions; are relatively independent of developmental stage, age, or general intelligence (IQ); and should demonstrate lower inter-individual variability than younger processes (Reber Reference Reber1992). If this is true, then several dissociating characteristics should be observable for D&dH's somatosensory pathways. For example, incidents of neurological disruption to the more explicit perceptual pathway should be more numerous than to the more implicit action pathway. If we assume that conscious information is processed in working memory, then we would also expect disruption to the processing of information from the perceptual pathway when working memory is occupied with a demanding secondary task. Disruption to information from the action pathway should be seen only when it has been made conscious.

In conclusion, the idea that the internal representation of a body schema is always unconscious may be flawed. It is possible that in certain circumstances the information becomes directly or indirectly accessible to consciousness. Given the high degree of interaction between the two pathways and the possibility of cross talk, noted by D&dH, this seems a plausible suggestion. However, current evidence suggests that elevating body schema information to the level of conscious awareness will be detrimental to the performance of skilled movement.