The multiple process model of goal-directed aiming/reaching: insights on limb control from various special populations.

Several years ago, our research group forwarded a model of goal-directed reaching and aiming that describes the processes involved in the optimization of speed, accuracy, and energy expenditure Elliott et al. (Psychol Bull 136:1023-1044, 2010). One of the main features of the model is the distinction between early impulse control, which is based on a comparison of expected to perceived sensory consequences, and late limb-target control that involves a spatial comparison of limb and target position. Our model also emphasizes the importance of strategic behaviors that limit the opportunity for worst-case or inefficient outcomes. In the 2010 paper, we included a section on how our model can be used to understand atypical aiming/reaching movements in a number of special populations. In light of a recent empirical and theoretical update of our model Elliott et al. (Neurosci Biobehav Rev 72:95-110, 2017), here we consider contemporary motor control work involving typical aging, Down syndrome, autism spectrum disorder, and tetraplegia with tendon-transfer surgery. We outline how atypical limb control can be viewed within the context of the multiple-process model of goal-directed reaching and aiming, and discuss the underlying perceptual-motor impairment that results in the adaptive solution developed by the specific group.

Enhancing technical skill learning through interleaved mixed-model observational practice.

A broad foundation of behavioural (Hayes et al. in Exp Brain Res 204(2): 199-206, 2010) and neurophysiological (Kohler et al. in Science 297(5582): 846-848, 2002) evidence has revealed that the acquisition of psychomotor skills, including those germane to clinical practice (Domuracki et al. in Med Educ 49(2): 186-192, 2015), can be facilitated through observational practice. Interestingly, research also reveals that learning via observation is greatest when the learner has the opportunity to view both error-free expert demonstrations and flawed novice demonstrations (Rohbanfard and Proteau in Exp Brain Res 215: 183-197, 2011). In this study, we explored whether the learning that results from the combined viewing of experts and novices is greater when the demonstrations are presented under observation schedules characterized by higher levels of contextual interference. To do so, we engaged participants in an observational learning study of the Fundamentals of Laparoscopic Surgery pots-and-beans task: a simulated procedure in which performers must move objects under precision constraints in the minimal access surgery environment. Each participant was randomized to one of three groups that engaged in identical physical and mixed-model observational practice of this skill, with the only difference being that one group's observation was presented in blocked fashion (low interference) while the other two groups' observations were presented in semi-interleaved (medium interference) and interleaved (high interference) fashions. Total errors and time-to-complete measures taken during physical practice blocks revealed that all three groups improved over the intervention. Further analyses revealed that the low interference group performed better immediately following the physical and observational practice intervention, but that the medium- and high-interference groups were conveyed a performance advantage in a transfer test conducted after a period of retention that challenged participants to perform in the opposite direction. The results are discussed with respect to the classic contextual interference effect (Shea and Morgan in J Exp Psychol 5(2): 179-187, 1979) and with particular relevance to clinical skills education.

The art of medicine: arts-based training in observation and mindfulness for fostering the empathic response in medical residents.

Empathy is an essential attribute for medical professionals. Yet, evidence indicates that medical learners' empathy levels decline dramatically during medical school. Training in evidence-based observation and mindfulness has the potential to bolster the acquisition and demonstration of empathic behaviours for medical learners. In this prospective cohort study, we explore the impact of a course in arts-based visual literacy and mindfulness practice (Art of Seeing) on the empathic response of medical residents engaged in obstetrics and gynaecology and family medicine training. Following this multifaceted arts-based programme that integrates the facilitated viewing of art and dance, art-making, and mindfulness-based practices into a practitioner-patient context, 15 resident trainees completed the previously validated Interpersonal Reactivity Index, Compassion, and Mindfulness Scales. Fourteen participants also participated in semistructured interviews that probed their perceived impacts of the programme on their empathic clinical practice. The results indicated that programme participants improved in the Mindfulness Scale domains related to self-confidence and communication relative to a group of control participants following the arts-based programme. However, the majority of the psychometric measures did not reveal differences between groups over the duration of the programme. Importantly, thematic qualitative analysis of the interview data revealed that the programme had a positive impact on the participants' perceived empathy towards colleagues and patients and on the perception of personal and professional well-being. The study concludes that a multifaceted arts-based curriculum focusing on evidence-based observation and mindfulness is a useful tool in bolstering the empathic response, improving communication, and fostering professional well-being among medical residents.

The relationship between perceived preceptor power use and student empowerment during clerkship rotations: a study of hidden curriculum.

CONTEXT: Medical learners are vulnerable to the social power used by preceptors. Furthermore, an individual's perceived level of personal empowerment has been identified as a predictor of positive behaviour in education environments. The degree to which medical students feel empowered in their clinical environments factors largely into how vulnerable they are to having their professional values influenced negatively by structural and cultural aspects of these environments. OBJECTIVES: The goal of this study was to explore the relationship between clerks' perceptions of personal empowerment and the social power employed by their preceptors. This research also investigates the prevalence of negative power use as a function of the hierarchical organisation of a clerkship rotation. METHODS: Validated power use and empowerment surveys were modified for clinical learning environments and administered to clerkship learners across six clerkship rotations. The outcomes of the two surveys were subjected to correlational analyses. Outcomes associated with the use of each type of perceived power were analysed to determine the influence of the relative involvement of residents and staff physicians in preceptorship. RESULTS: Correlational analyses revealed strong relationships between clerks' perceptions of preceptor power use and their own personal empowerment. Furthermore, although participants perceived significantly more pro-social preceptor uses of power, clerks perceived a higher prevalence of coercive power on rotations with high involvement of residents as preceptors. CONCLUSIONS: Clerks' perceptions of empowerment correlate positively with positive power bases and negatively with negative dimensions of preceptor power. This research has implications for the importance of the development of resident and faculty staff as educators, the identification of clerks who are vulnerable to ethical violation, and for a refined understanding of the transactional way in which power is experienced in a medical education context.

OSCE circuit performance effects: Does circuit order influence scores?

It is not uncommon for medical students to raise concerns over the difficulty of a single station within an Objective Structured Clinical Examination (OSCE), particularly when they feel they were subject to an unfair situation. Indeed, test developers also share these concerns about the possibility that a single extremely difficult station may impact student performance on the station that follows. As a reaction to the concerns of both students and examiners, we conducted a study, analyzing the scores of multiple OSCEs. Although our analyses did not support the complaints of unfairness targeted at the OSCE, we feel it is a rather enlightening story nevertheless, and one worth sharing.

The impacts of observing flawed and flawless demonstrations on clinical skill learning.

OBJECTIVES: Clinical skills expertise can be advanced through accessible and cost-effective video-based observational practice activities. Previous findings suggest that the observation of performances of skills that include flaws can be beneficial to trainees. Observing the scope of variability within a skilled movement allows learners to develop strategies to manage the potential for and consequences associated with errors. This study tests this observational learning approach on the development of the skills of central line insertion (CLI). METHODS: Medical trainees with no CLI experience (n = 39) were randomised to three observational practice groups: a group which viewed and assessed videos of an expert performing a CLI without any errors (F); a group which viewed and assessed videos that contained a mix of flawless and errorful performances (E), and a group which viewed the same videos as the E group but were also given information concerning the correctness of their assessments (FA). All participants interacted with their observational videos each day for 4 days. Following this period, participants returned to the laboratory and performed a simulation-based insertion, which was assessed using a standard checklist and a global rating scale for the skill. These ratings served as the dependent measures for analysis. RESULTS: The checklist analysis revealed no differences between observational learning groups (grand mean ± standard error: [20.3 ± 0.7]/25). However, the global rating analysis revealed a main effect of group (d.f.2,36 = 4.51, p = 0.018), which describes better CLI performance in the FA group, compared with the F and E groups. CONCLUSIONS: Observational practice that includes errors improves the global performance aspects of clinical skill learning as long as learners are given confirmation that what they are observing is errorful. These findings provide a refined perspective on the optimal organisation of skill education programmes that combine physical and observational practice activities.

Family medicine residents' practice intentions: Theory of planned behaviour evaluation.

OBJECTIVE: To assess residents' practice intentions since the introduction of the College of Family Physicians of Canada's Triple C curriculum, which focuses on graduating family physicians who will provide comprehensive care within traditional and newer models of family practice. DESIGN: A survey based on Ajzen's theory of planned behaviour was administered on 2 occasions. SETTING: McMaster University in Hamilton, Ont. PARTICIPANTS: Residents (n = 135) who were enrolled in the Department of Family Medicine Postgraduate Residency Program at McMaster University in July 2012 and July 2013; 54 of the 60 first-year residents who completed the survey in 2012 completed it again in 2013. MAIN OUTCOME MEASURES: The survey was modeled so as to measure the respondents' intentions to practise with a comprehensive scope; determine the degree to which their attitudes, subjective norms, and perceptions of control about comprehensive practice influence those intentions; and investigate how these relationships change as residents progress through the curriculum. The survey also queried the respondents about their intentions with respect to particular medical services that underpin comprehensive practice. RESULTS: The responses indicate that the factors modeled by the theory of planned behaviour survey account for 60% of the variance in the residents' intentions to adopt a comprehensive scope of practice upon graduation, that there is room for curricular improvement with respect to encouraging residents to practise comprehensive care, and that targeting subjective norms about comprehensive practice might have the greatest influence on improving resident intentions. CONCLUSION: The theory of planned behaviour presents an effective approach to assessing curricular effects on resident practice intentions while also providing meaningful information for guiding further program evaluation efforts in the Department of Family Medicine at McMaster University.

The impact of an arts-based programme on the affective and cognitive components of empathic development.

Medical education research demonstrates that empathic behaviour is amenable to positive change when targeted through educational programmes. This study evaluates the impact of an arts-based intervention designed to nurture learner empathy through the provision of facilitated visual literacy activities. Health Sciences students (N=19) were assigned to two learning groups: a group that participated in a visual literacy programme at the McMaster Museum of Art and a control group that participated in the normal Health Sciences curriculum. All participants completed an inter-reactivity index, which measures empathy on affective and cognitive levels, prior to and following the programme. Those individuals assigned to the visual literacy programme also completed open-ended questions concerning the programme's impact on their empathic development. The index scores were subjected to independent within-group, between-test analyses. There was no significant impact of the programme on the participants' overall empathic response. However, sub-component analyses revealed that the programme had a significant positive effect on cognitive aspects of empathy. This finding was substantiated by the narrative reports. The study concludes that the affective focus of humanities-based education needs to be enhanced and recommends that learners are educated on the different components that comprise the overall empathic response.

Information processing, specificity of practice, and the transfer of learning: considerations for reconsidering fidelity.

Much has been made in the recent medical education literature of the incorrect characterization of simulation along a continuum of low to high fidelity (Cook et al. JAMA 306(9): 978-988, 2011; Norman et al. Med Educ 46(7): 636-647, 2012; Teteris et al. Adv Health Sci Educ 17(1): 137-144, 2012). For the most part, the common definition within the medical education community has been that simulations that present highly realistic performance characteristics, contexts, and scenarios are referred to as high-fidelity, while simulations that reduce to-be-learned skills to simpler constructs or constituent parts are referred to as low-fidelity. The issue with this is that highly-realistic has tended to mean the degree to which the simulation looks like the criterion context with little regard for what features of the simulation are in fact relevant to the skill that the educator hopes to teach. The inherent assumption that high fidelity simulations lead to better learning-an assumption for which there is a lack of supporting evidence (Norman et al. Med Educ 46(7): 636-647, 2012)-only exacerbates the problem. So much so that some have suggested that the term be abandoned all together (Hamstra et al. Acad Med J Assoc Am Med Coll 2014). While, it is true that fidelity and its importance are misconstrued in the medical education literature, the construct, defined classically as the degree of faithfulness that exists between two entities, is still fundamental to understanding the effectiveness that any one simulation might have in preparing learners for clinical performance. However, the concept of simulation fidelity must be recast in terms of the fundamental information processing events that underpin human performance.

Predicting international medical graduate success on college certification examinations: responding to the Thomson and Cohl judicial report on IMG selection.

OBJECTIVE: To determine predictors of international medical graduate (IMG) success in accordance with the priorities highlighted by the Thomson and Cohl judicial report on IMG selection. DESIGN: Retrospective assessment using regression analyses to compare the information available at the time of resident selection with those trainees' national certification examination outcomes. SETTING: McMaster University in Hamilton, Ont. PARTICIPANTS: McMaster University IMG residents who completed the program between 2005 and 2011. MAIN OUTCOME MEASURES: Associations between IMG professional experience or demographic characteristics and examination outcomes. RESULTS: The analyses revealed that country of study and performance on the Medical Council of Canada Evaluating Examination are among the predictors of performance on the College of Family Physicians of Canada and the Royal College of Physicians and Surgeons of Canada certification examinations. Of interest, the analyses also suggest discipline-specific relationships between previous professional experience and examination success. CONCLUSION: This work presents a useful technique for further improving our understanding of the performance of IMGs on certification examinations in North America, encourages similar interinstitutional analyses, and provides a foundation for the development of tools to assist with IMG education.

Cognitive Load Theory: Implications for Nursing Education and Research.

This article provides an overview of cognitive load theory (CLT) and explores applications of CLT to health profession and nursing education research, particularly for multimedia and simulation-based applications. The article first reviews the 3 components of cognitive load: intrinsic, extraneous, and germane. It then discusses strategies for manipulating cognitive load variables to enhance instruction. Examples of how CLT variables can be modulated during instruction are provided. Lastly, the article discusses current applications of CLT to health profession and nursing education research and presents future research directions, focusing on the areas of multimedia and simulation-based learning.

Le présent article offre un aperçu de la théorie de la charge cognitive (TCC) et explore les applications de la TCC dans la recherche sur la formation des professionnels de la santé et des soins infirmiers, plus particulièrement les applications multimédias et fondées sur la simulation. L'article revoit tout d'abord les trois types de charge cognitive: intrinsèque, extrinsèque et germane. Il examine ensuite les stratégies permettant de manipuler les variables de la charge cognitive en vue d'améliorer l'enseignement. Des exemples montrant comment les variables de la TCC peuvent être modulées pendant l'enseignement sont fournis. Enfin, l'article discute les applications actuelles de la TCC dans le domaine de la recherche sur la formation des professionnels de la santé et des soins infirmiers et présente les orientations futures de la recherche, l'accent étant mis sur les secteurs de l'apprentissage multimédia et fondé sur la simulation.

The influence of target context and early and late vision on goal-directed reaching.

The online visual control of movement involves contributions from 2 processes: a process early in the trajectory concerned with comparisons between actual and expected sensory consequences and another process late in the trajectory that reduces the discrepancy between the position of the hand and the target. This experiment was designed to determine how early and late visual controls are impacted by the illusory characteristics of the target in a rapid reaching task. Participants performed 500 ms movements to the vertices of Müller-Lyer figures with the availability of full vision on the majority of trials. However, on a fraction of the trials, movements to the targets were performed with either early vision (first 200 ms of movement), late vision (last 200 ms of movement) or no vision. Although participants undershoot the targets under all target and visual conditions, the impact of the target configuration was greatest when vision was available during only the final portion of the movement trajectory and least when only early vision was available for limb regulation. Aiming bias under full-vision and no-vision conditions was intermediate. These findings indicate that visual context has a greater impact on late discrete limb regulation than on early dynamic control of the limb trajectory.

Gaze-down endoscopic practise leads to better novice performance on gaze-up displays.

OBJECTIVES: It is well known that precision skills are best learned when they are practised in the sensorimotor context that is present when performance is most important. However, a particular skill may vary with respect to the sensorimotor context in which it is performed. Certain sensorimotor variations can make a task more or less complex than others. Recent accounts of skill learning describe how task difficulty can be manipulated to provide optimised challenges to progress learners beyond their current level of expertise. This study tests the idea that simplified practise contexts lead novice learners to acquire skill proficiency that is more generalisable to new contexts. METHODS: We present a learning experiment in which the performances of novices who acquired a set level of proficiency in the endoscopic pots-and-beans task through performance-based practise using a gaze-up endoscopic monitor arrangement were compared against the performances of novices who acquired an equivalent level of proficiency using a simplified gaze-down arrangement. Participants returned after 1 week for retention and transfer testing. RESULTS: Time and accuracy analyses revealed that participants in both training groups improved significantly over the practise protocol and maintained this performance after a period of retention. However, the comparisons of the visual display transfer performances (i.e. on the gaze-up arrangement) of the gaze-down trainees against the retention performances (i.e. also on the gaze-up arrangement) of their gaze-up counterparts and vice versa revealed that gaze-down trainees made fewer errors in both performance contexts (F(1,16) = 7.97, p = 0.01 and F(1,16) = 57.05, p = 0.04, respectively). CONCLUSIONS: These findings highlight the benefits associated with using simplified sensorimotor practise contexts for novice learners. Beginners will learn best from simplified practise because it allows them to develop good movement strategies for dealing with potential error without being overwhelmed by task complexity.

The roles of deliberate practice and innate ability in developing expertise: evidence and implications.

CONTEXT: Medical education research focuses extensively on experience and deliberate practice (DP) as key factors in the development of expert performance. The research on DP minimises the role of individual ability in expert performance. This claim ignores a large body of research supporting the importance of innate individual cognitive differences. We review the relationship between DP and an innate individual ability, working memory (WM) capacity, to illustrate how both DP and individual ability predict expert performance. METHODS: This narrative review examines the relationship between DP and WM in accounting for expert performance. Studies examining DP, WM and individual differences were identified through a targeted search. RESULTS: Although all studies support extensive DP as a factor in explaining expertise, much research suggests individual cognitive differences, such as WM capacity, predict expert performance after controlling for DP. The extent to which this occurs may be influenced by the nature of the task under study and the cognitive processes used by experts. The importance of WM capacity is greater for tasks that are non-routine or functionally complex. Clinical reasoning displays evidence of this task-dependent importance of individual ability. CONCLUSIONS: No single factor is both necessary and sufficient in explaining expertise, and individual abilities such as WM can be important. These individual abilities are likely to contribute to expert performance in clinical settings. Medical education research and practice should identify the individual differences in novices and experts that are important to clinical performance.

The role of collaborative interactivity in the observational practice of clinical skills.

CONTEXT: Video-based observational practice can extend simulation-based learning outside the training space. This study explores the value of collaborative feedback provided during observational practice to the acquisition of clinical skills. METHODS: Nursing students viewed a video demonstrating the proper ventrogluteal injection technique before performing a videotaped pre-test trial on a simulator. They were then assigned randomly to one of three observational practice groups: a group that observed the expert demonstration (EO group); a group that viewed the expert demonstration, self-assessed their individual pre-test and contrasted their self-assessments with expert feedback (ESO group), and a group that observed the expert demonstration, self-assessed and contrasted their assessments with those of an expert, and formed a community that engaged in peer-to-peer feedback (ESPO group). The observation of all videos, the provision of assessments and all networking occurred via an Internet-mediated network. After 2 weeks, participants returned for post-tests and transfer tests. RESULTS: The pre-test-post-test analyses revealed significant interactions (global rating scale: F((2,22)) =4.00 [p =0.033]; checklist: F((2,22)) =4.31 [p =0.026]), which indicated that post-test performance in the ESPO group was significantly better than pre-test performance. The transfer analyses revealed main effects for both the global rating scale (F((2,23)) =6.73; p =0.005) and validated checklist (F((2,23)) =7.04; p =0.004) measures. Participants in the ESPO group performed better on the transfer test than those in the EO group. CONCLUSIONS: The results suggest that video-based observational practice can be effective in extending simulation-based learning, but its effectiveness is mediated by the amount of time the learner spends engaged in the practice and the type of learning activities the learner performs in the observational practice environment. We speculate that increasing collaborative interactivity supports observational learning by increasing the extent to which the educational environment can accommodate learners' specific needs.

Colour-induced relationship between affect and reaching kinematics during a goal-directed aiming task.

A link between affect and action has been supported by the discovery that threat information is prioritized through an action-centred pathway--the dorsal visual stream. Magnocellular afferents, which originate from the retina and project to dorsal stream structures, are suppressed by exposure to diffuse red light, which diminishes humans' perception of threat-based images. In order to explore the role of colour in the relationship between affect and action, participants donned different pairs of coloured glasses (red, yellow, green, blue and clear) and completed Positive and Negative Affect Scale questionnaires as well as a series of target-directed aiming movements. Analyses of affect scores revealed a significant main effect for affect valence and a significant interaction between colour and valence: perceived positive affect was significantly smaller for the red condition. Kinematic analyses of variable error in the primary movement direction and Pearson correlation analyses between the displacements travelled prior to and following peak velocity indicated reduced accuracy and application of online control processes while wearing red glasses. Variable error of aiming was also positively and significantly correlated with negative affect scores under the red condition. These results suggest that only red light modulates the affect-action link by suppressing magnocellular activity, which disrupts visual processing for movement control. Furthermore, previous research examining the effect of the colour red on psychomotor tasks and perceptual acceleration of threat-based imagery suggest that stimulus-driven motor performance tasks requiring online control may be particularly susceptible to this effect.

Action representations in perception, motor control and learning: implications for medical education.

OBJECTIVES: the motor behaviours or 'actions' that provide the basis for precision limb control, including the performance of complex medical procedures, are represented at different levels in the central nervous system. This review focuses on how these representations influence the way people perceive, execute and learn goal-directed movements. PERCEPTION AND ATTENTION: the neural processes associated with paying attention to an object are part and particle of the same processes engaged to physically interact with that object. The automatic way in which specific actions are engaged makes it important that we structure perceptual motor environments in a manner that facilitates goal actions and minimises the likelihood of unwanted actions. MOTOR CONTROL: most actions are organised to optimise speed, accuracy and energy expenditure while avoiding worst-case outcomes. To achieve a good outcome on movements, the performer must have the opportunity to experiment with the way specific actions are executed. Early in the discovery process, errors are necessary if the performer is to determine his or her performance boundaries. motor learning: as learning progresses, representations of action become predictive. For example, if rapid corrective processes are to operate, the performer needs to anticipate sensorimotor consequences of movement. Thus, practice should be specific to the conditions under which actions are performed, and the performer. Although nothing can replace physical practice, complex representations of action can develop by observing both expert performers and learners. In many cases, practice scenarios that include both physical practice and observations of other learners can be the most efficient use of time and resources. CONCLUSIONS: although most of the experiments reviewed here involved laboratory tasks such as rapid aiming and movement sequencing, the majority of the principles apply to motor control and learning in more complex situations. Thus, they should be considered when developing methods to train medical personnel to perform perceptual motor procedures with precision.

Motor adaptation and manual transfer: insight into the persistent nature of sensorimotor representations.

It is well known that sensorimotor memories are built and updated through experience with objects. These representations are useful to anticipatory and feedforward control processes that preset grip and load forces during lifting. When individuals lift objects with qualities that are not congruent with their memory-derived expectations, feedback processes adjust motor plans to achieve successful lifts and contribute to the updating of the stored representations. The two experiments presented examine motor adaptation to an illusory size-weight lifting task, and the transfer of this motor adaptation to the unexposed hand. In Experiment 1, performers acquired motor adaptation with their right hand and transfer was measured on their left hand. In Experiment 2, adaptation was acquired with the left hand and transfer was measured on the right hand. In order to investigate the persistence of sensorimotor memories, these experiments measure adaptation, retention, and transfer after 15min and 24h delay periods. Both experiments confirm that experience with objects leads to adaptation of force scaling processes, that these adaptations transcend effector and are persistent. The results are discussed in terms favouring interpretations that describe motor adaptations to illusion as being centrally available.

Early Impulse Control: Treatment of Potential Errors within Pre-Programming and Control.

Early aiming adjustments following an online perturbation are made possible by impulse control. This process may unfold even earlier when perturbations impose a greater risk of a costly overshoot error. Participants executed upward and downward aims to mediate the cost of potential errors-downward overshoots require more energy to correct against gravity. On 33% of the trials, texture elements on the aiming surface were shifted following onset to appear congruent or incongruent with the aiming direction, and consequently generate a misperception of the limb moving slower or faster, respectively. Thus, the risk of potential errors could be influenced by the online perturbation (e.g., increased perceived likelihood of overshooting following the incongruent background). Findings indicated greater undershooting for down compared to up, which reflects the principle of movement optimisation. There was also more undershooting for an incongruent compared to congruent background, which is consistent with early online adjustments counter-acting the misperceived limb velocity. However, there were no interactions throughout the movement trajectory. We suggest that while the initial pre-programme considers the cost of potential errors (target direction), early impulse control fails to discriminate the likelihood of these errors occurring following an online perturbation (moving background).

The impact of real and illusory target perturbations on manual aiming.

This experiment was designed to determine if real and illusory shifts in target position at movement initiation affect the same online corrective processes. Adult participants completed rapid goal-directed movements toward the vertex of a target "T" located at the midline, 25 cm distal to a small home position. At movement initiation, the target either stayed the same, shifted its real position, its illusory position or both. The real perturbation involved a 2.5 mm shift either toward or away from the body. For the illusory perturbation, the horizontal portion of the "T" changed to inward or outward Müller-Lyer wings. Both the real and the illusory perturbation affected movement outcome. The two manipulations began to have their impact at peak velocity. Because both perturbations affected mid to late trajectory control and because their effects were not independent, we concluded that real and illusory target shifts impact late visual motor control associated with a comparison between the position of the limb and the perceived position of the target.