Skill theory v2.0: dispositions,emulation, and spatial perception

An attempt is made to defend a general approach to the spatial content of perception, an approach according to which perception is imbued with spatial content in virtue of certain kinds of connections between perceiving organism’s sensory input and its behavioral output. The most important aspect of the defense involves clearly distinguishing two kinds of perceptuo-behavioral skills—the formation of dispositions, and a capacity for emulation. The former, the formation of dispositions, is argued to by the central pivot of spatial content. I provide a neural information processing interpretation of what these dispositions amount to, and describe how dispositions, so understood, are an obvious implementation of Gareth Evans’ proposal on the topic. Furthermore, I describe what sorts of contribution are made by emulation mechanisms, and I also describe exactly how the emulation framework differs from similar but distinct notions with which it is often unhelpfully confused, such as sensorimotor contingencies and forward models.     

The antinomy of perception: Merleau-Ponty and causal representation theory

This essay has benefited from discussions with Arthur Melnick, Frederick Schmitt, and Richard Schacht — all of whom had helpful and insightful suggestions at various stages of its conceptualization. I am also particularly indebted to Marjorie Hass who has repeatedly listened to it with a keen philosophical ear and significantly guided its formation.     

The motor theory of speech perception revisited

Galantucci, Fowler, and Turvey (2006) have claimed that perceiving speech is perceiving gestures and that the motor system is recruited for perceiving speech. We make the counter argument that perceiving speech is not perceiving gestures, that the motor system is not recruitedfor perceiving speech, and that speech perception can be adequately described by a prototypical pattern recognition model, the fuzzy logical model of perception (FLMP). Empirical evidence taken as support for gesture and motor theory is reconsidered in more detail and in the framework of the FLMR Additional theoretical and logical arguments are made to challenge gesture and motor theory.     

The motor theory of speech perception reviewed

More than 50 years after the appearance of the motor theory of speech perception, it is timely to evaluate its three main claims that (1) speech processing is special, (2) perceiving speech is perceiving gestures, and (3) the motor system is recruited for perceiving speech. We argue that to the extent that it can be evaluated, the first claim is likely false. As for the second claim, we review findings that support it and argue that although each of these findings may be explained by alternative accounts, the claim provides a single coherent account. As for the third claim, we review findings in the literature that support it at different levels of generality and argue that the claim anticipated a theme that has become widespread in cognitive science.     

Studying action representation in children via motor imagery

The use of motor imagery is a widely used experimental paradigm for the study of cognitive aspects of action planning and control in adults. Furthermore, there are indications that motor imagery provides a window into the process of action representation. These notions complement internal model theory suggesting that such representations allow predictions (estimates) about the mapping of the self to parameters of the external world; processes that enable successful planning and execution of action. The ability to mentally represent action is important to the development of motor control. This paper presents a critical review of motor imagery research conducted with children (typically developing and special populations) with focus on its merits and possible shortcomings in studying action representation. Included in the review are age-related findings, possible brain structures involved, experimental paradigms, and recommendations for future work. The merits of this review are associated with the apparent increasing attraction for using and studying motor imagery to understand the developmental aspects of action processing in children.     

The memory representation of motor skills: a test of schema theory

Currently, a popular model for the central representation of motor skills is embodied in Schmidt's schema theory of discrete motor skill learning (Schmidt, 1975). Two experiments are reported here that contrast predictions from a schema abstraction model that is the basis for schema theory with those from an exemplar-based model of motor skill memory representation. In both experiments, subjects performed 300 trials per day of three variations of a three-segment timing task over 4 days of acquisition. The subjects then either immediately transferred to four novel variations of the same task (Experiment 1) that varied in degree of similarity to the exemplars experienced during acquisition; or performed two novel and two previously produced exemplars, following 24-h and 1-week retention intervals (Experiment 2). The results indicated that novel task transfer was not affected by the degree of similarity between the acquisition and transfer exemplars, and that there was no advantage for a previously produced exemplar over a novel exemplar after either a 24-hr or 1 week retention interval. Also, in both experiments, a consistent pattern of bias in responding was noted for novel task transfer and retention. These results are indicative of a schema abstraction model of memory representation for motor skills.     

Locational representation in imagery: The third dimension

Six experiments were conducted to test the relative processing characteristics of picture-plane and three-dimensional imagery as indexed by tasks that required subjects to keep track of successive locations in multiunit visual displays. Subjects were shown symmetrical displays either drawn on cardboard or constructed with three-dimensional blocks. They then were required to imagine these matrices and follow pathways through a series of adjacent squares (blocks) within the matrices. The pathways were described by a series of verbal terms that indicated the direction of the next square (block) in the pathway. Subjects experienced difficulty in performing the task with picture-plane displays composed of as few as 16 squares (4×4), but they rarely made errors with a three-dimensional matrix of 27 blocks (3×3×3). Performance with the three-dimensional task dropped dramatically when the matrix size was increased to 4×4×4. The results replicated previous findings that the image processing capacity for location in two-dimensional imagery is about three units in each direction, and they indicate that adding the depth dimension increases the capacity for representation of spatial location in imagery.     

Eye gaze metrics reflect a shared motor representation for action observation and movement imagery

Action observation (AO) and movement imagery (MI) have been reported to share similar neural networks. This study investigated the congruency between AO and MI using the eye gaze metrics, dwell time and fixation number. A simple reach-grasp-place arm movement was observed and, in a second condition, imagined where the movement was presented from the first person perspective (1PP) and the third person perspective (3PP). Dwell time and number of fixations were calculated for whole scene and regions of interest (ROIs). For whole scene, no significant differences were found in the number of fixations for condition (AO, MI) or perspective. Dwell time, however, was significantly longer in AO than MI. For ROIs, the number of fixations was significantly greater in 1PP than 3PP. The data provide support for congruence between motor simulation states but also indicate some functional differences.     

The representation of conceptual knowledge: visual,auditory, and olfactory imagery compared with semantic processing

Two experiments comparing imaginative processing in different modalities and semantic processing were carried out to investigate the issue of whether conceptual knowledge can be represented in different format. Participants were asked to judge the similarity between visual images, auditory images, and olfactory images in the imaginative block, if two items belonged to the same category in the semantic block. Items were verbally cued in both experiments. The degree of similarity between the imaginative and semantic items was changed across experiments. Experiment 1 showed that the semantic processing was faster than the visual and the auditory imaginative processing, whereas no differentiation was possible between the semantic processing and the olfactory imaginative processing. Experiment 2 revealed that only the visual imaginative processing could be differentiated from the semantic processing in terms of accuracy. These results showed that the visual and auditory imaginative processing can be differentiated from the semantic processing, although both visual and auditory images strongly rely on semantic representations. On the contrary, no differentiation is possible within the olfactory domain. Results are discussed in the frame of the imagery debate.     

The emergence of motor imagery in children

A total of 80 children (40 5-year-olds and 40 7-year-olds) took part in an experiment to evaluate their capacity to mentally evoke a motor image of their own displacement. Using a chronometry paradigm, movement duration was compared in a task where children were asked to move in order to take a puppet back to its home (actual) and to think about themselves executing the same action (virtual). Movement durations for actual and virtual displacements were obtained in two conditions, where either no information was provided about the weight of the puppet to be displaced (standard situation) or the puppet was described as being heavy (informed situation). A significant correlation between actual and virtual walking durations was observed for 7-year-olds in the informed condition. This result provides evidence for a motor imagery process emerging in 7-year-olds when children are required to think about themselves in action.     

Age-related changes in motor imagery from early childhood to adulthood: Probing the internal representation of speed-accuracy trade-offs

The purpose of this study was to chart the development of motor imagery ability between 5 and 29 years of age and its relationship to fine-motor skill. 237 participants performed a computerized Virtual Radial Fitts Task (VRFT) as a measure of Motor Imagery (MI) ability. Participants aimed at five targets, positioned along radial axes from a central target circle. The targets differed in width over trials (2.5, 5, 10, 20 or 40 mm). Performance was indexed by the relationship between the movement time (MT) in executed and imagined movements. A subset of participants (11–19 years old, n = 22) also performed the task with their non-preferred hand. We also examined if manual skill (measured by peg board task and posting coins) was related to the executed and imagined MT on the VRFT. Our results showed that the accuracy of the imagined movement improved steadily over childhood, reaching an asymptote during adolescence and into early adulthood. The correlation between the real and virtual MT using the preferred hand did not differ appreciably from that using the non-preferred hand. If the children could perform the tasks with their non-preferred hand (11 years and older), they also scaled performance in relatively precise terms using the less dextrous non-preferred hand. The correlation between real MT on the VRFT and fine-motor performance ranged between .53 and .42, while that for virtual movement was between .37 and .34. MI ability predicts manual skill to a moderate degree.     

Assessing relations between imagery and perception

Direct comparisons between perceptual performance and reports made under imagery instructions are uninterpretable except in cases where (a) the perceptual phenomenon is well understood and (b) experimental constraints are sufficient to establish imagery causally in the effect. Neither condition seems to be satisfied in Finke and Kurtzman's article. Furthermore, if imagery is an internal medium conceived in introspective terms, the second condition can never be met because the medium is not accessible to operational definition. Perhaps the basic problem with this research is that the instructions used to create conditions in imagery experiments do not qualify as operational definitions. Reports of successful compliance with imagery instructions are logically equivalent to introspective reports.     

Perception and imagination: amodal perception as mental imagery

When we see an object, we also represent those parts of it that are not visible. The question is how we represent them: this is the problem of amodal perception. I will consider three possible accounts: (a) we see them, (b) we have non-perceptual beliefs about them and (c) we have immediate perceptual access to them, and point out that all of these views face both empirical and conceptual objections. I suggest and defend a fourth account, according to which we represent the occluded parts of perceived objects by means of mental imagery. This conclusion could be thought of as a (weak) version of the Strawsonian dictum, according to which “imagination is a necessary ingredient of perception itself”.     

Interference effects demonstrate distinct roles for visual and motor imagery during the mental representation of human action

Four experiments were completed to characterize the utilization of visual imagery and motor imagery during the mental representation of human action. In Experiment 1, movement time functions for a motor imagery human locomotion task conformed to a speed-accuracy trade-off similar to Fitts' Law, whereas those for a visual imagery object motion task did not. However, modality-specific interference effects in Experiment 2 demonstrate visual and motor imagery as cooperative processes when the action represented is tied to visual coordinates in space. Biomechanic-specific motor interference effects found in Experiment 3 suggest one basis for separation of processing channels within motor imagery. Finally, in Experiment 4 representations of motor actions were found to be generated using only visual imagery under certain circumstances: namely, when the imaginer represented the motor action of another individual while placed at an opposing viewpoint. These results suggest that the modality of representation recruited to generate images of human action is dependent on the dynamic relationship between the individual, movement, and environment.