The relative nature of perception:a response to Canal-Bruland and van der Kamp (2015)

Cañal-Bruland and van der Kamp (2015) present an argument about the incommensurate relationship between affordance perception and spatial perception in a criticism of Proffitt and Linkenauger (2013)’s phenotypic approach to perception. Many of their criticisms are based on a difference in the interpretation of the core ideas underlying the phenotypic approach. The most important of these differences in interpretations concern fundamental assumptions about the nature of the perceptions of size and distance themselves. Extent perception must be relative to the organism; therefore, there can be no veridical perception of space. Also, we argue in the phenotypic approach that space perception is an emergent property of affordance perception; they are not different types of perceptions as Cañal-Bruland and van der Kamp presume. Thirdly, affordance perception need not be perfectly accurate, just good enough. Additionally, affordance perception need not be dichotomous; this presumption likely originates in the methodology typically employed to study affordance perception. Finally, I agree with Cañal-Bruland and van der Kamp that joint research efforts will clarify and improve our understanding of these issues

The Influence of Perceptual-Motor Variability on the Perception of Action Boundaries for Reaching

Successful interactions within the environment are contingent upon the perceiver’s ability to perceive the maximum extent over which they can perform actions, commonly referred to as action boundaries. Individuals are extremely calibrated to their action boundaries, and the perceptual system can quickly and flexibly recalibrate to changes in the size of action boundaries in the event of physiological and/or environmental changes. However, because even the most basic motor activities are subject to variability over time, the information upon which action boundaries are based must also be subject to variability. In this set of studies, we examined the effect of random and systematic variability in reaching experience on the perception of action boundaries for reaching using virtual reality. Participants were asked to estimate their reachability following experience reaching with either a long virtual arm, short virtual arm, or a virtual arm that varied in size. Overall, we found that individuals tended toward liberal estimates of their reachability; however, individuals can be influenced to be slightly more conservative after a higher percentage of short reaches. Consequently, when anticipating our reaching capability in the event of perceptual motor variability, individuals employ a liberal approach as it would result in the highest number of successful attempts. (PsycInfo Database Record (c) 2020 APA, all rights reserved

Action-specific effects in perception and their potential applications

Spatial perception is biased by action. Hills appear steeper and distances appear farther to individuals who would have to exert more effort to transverse the space. Objects appear closer, smaller, and faster when they are easier to obtain. Athletes who are playing better than others see their targets as bigger. These phenomena are collectively known as action-specific effects on perception. In this target article, we review evidence for action-specific effects, including evidence that they reflect genuine changes in perception, and speculate on possible applications of action’s influence on vision

Perceiving action boundaries for overhead reaching in a height-related situation

To successfully interact within our environment, individuals need to learn the maximum extent (or minimum) over which they can perform actions, popularly referred to as action boundaries. Because people learn such boundaries over time from perceptual motor feedback across different contexts, both environmental and physiological, the information upon which action boundaries are based must inherently be characterised by variability. With respect to reaching, recent work suggests that regardless of the type of variability present in their perceptual-motor experience, individuals favoured a liberal action boundary for horizontal reaching. However, the ways in which action boundaries are determined following perceptual-motor variability could also vary depending on the environmental context as well as the type of reach employed. The present research aimed to established whether the perceptual system utilises the same strategy for all types of reaches over different contexts. Participants estimated their overhead reachability following experience reaching with either a long or a short virtual arm, or a virtual arm that varied in length – while standing on the edge of a rooftop or standing on the ground. Results indicated that while similar strategies were used to determine action boundaries in both height- and non-height-related context, participants were significantly more conservative with their reachability estimates in the height-related context. Participants were sensitive to the probabilistic information associated with different arm’s reach they have experienced during the calibration phase, and used a weighted average of reaching experience to determine their action boundary under conditions of uncertaint

The influence of perceptual motor variability on the perception of action boundaries for reaching in a real-world setting

The ability to accurately perceive the extent over which one can act is requisite for the successful execution of visually-guided actions. Yet, like other outcomes of perceptual-motor experience, our perceived action boundaries are not stagnant, but in constant flux. Hence, the perceptual systems must account for variability in one’s action capabilities in order for the perceiver to determine when they are capable of successfully performing an action. Recent work has found that, after reaching with a virtual arm that varied between short and long each time they reach, individuals determine their perceived action boundaries using the most liberal reaching experience. However, these studies were conducted in virtual reality, and the perceptual systems may handle variability differently in a real-world setting. To test this hypothesis, we created a modified orthopaedic elbow brace that mimic injury in the upper limb by restricting elbow extension via remote control. Participants were asked to make reachability judgements after training in which the maximum extent of their reaching ability was either unconstricted, constricted or variable over several calibration trials. Findings from the current study didn’t conform to those in virtual reality; participants were more conservative with their reachability estimates after experiencing variability in a real-world setting

Can the Left Hand Benefit from being Right? The Influence of Body Side on Action Estimates

Right-handed individuals (RHIs) possess various perceptual, visual, and somatosensory biases that facilitate more precise and efficient control of the right hand. For example, RHIs have asymmetries in the cortical representation of both hands, with the right hand representation in left motor cortex being significantly larger than the left hand representation in right motor cortex. These biases have consequences on RHIs’ perceptions of their bodies, with them estimating their right hand and arm to be visually larger than their left. Subsequently, they estimate that they can reach further distances or grasp larger objects using their right hand than their left, despite no significant differences in the real morphology of the hands. One key question is whether such visual biases RHIs experience sufficiently explain these asymmetries in action perception between the left and right hand. This thesis aims to explore both the visual and non-visual (somatosensory) factors that underlie both the strong right-hand preference and impression of greater capabilities using the right hand in RHIs. To do this, virtual reality (VR) and motion capture technology were used in a series of 9 experiments to isolate visual feedback associated with moving the right hand from the somatosensory feedback that would ordinarily be experienced. Three of these 9 experiments explored the impact of visual feedback specifying handedness on perceptions of reaching and grasping abilities, four explored the ability for people to embody virtual limbs that are visually presented incongruently to somatosensory feedback, and two explored whether the left-hemisphere processing advantage for visually guided actions could be exploited in the context of visual illusions. Overall, the key findings of this thesis were that: 1) visual feedback specifying hand use did not have a significant impact on action estimates; 2) action estimates were based on the physical hand that was being used, and the right hand was estimated as more capable even when viewed as the left; 3) differences in action estimates between the left and right hands is contingent on the complexity of the action being performed. Thus, the findings suggest that RHIs’ perceptions of greater action capabilities with their right hand are primarily rooted in cortical asymmetries that lead to an enlarged sensorimotor representation of the right hand. Moreover, more efficient sensory feedback aside from vision better accounts for differences in action perception than visual feedback specifying the hand being moved during visually guided actions. The findings of this thesis have broader implications for understanding the factors that underlie biases in action perception in RHIs

Asymmetrical Body Perception: A Possible Role for Neural Body Representations

Perception of one\u27s body is related not only to the physical appearance of the body, but also to the neural representation of the body. The brain contains many body maps that systematically differ between right- and left-handed people. In general, the cortical representations of the right arm and right hand tend to be of greater area in the left hemisphere than in the right hemisphere for right-handed people, whereas these cortical representations tend to be symmetrical across hemispheres for left-handers. We took advantage of these naturally occurring differences and examined perceived arm length in right- and left-handed people. When looking at each arm and hand individually, right-handed participants perceived their right arms and right hands to be longer than their left arms and left hands, whereas left-handed participants perceived both arms accurately. These experiments reveal a possible relationship between implicit body maps in the brain and conscious perception of the body

Motor imagery vividness and symptom severity in Parkinson's disease

Motor imagery (MI), the mental rehearsal of an action in the absence of overt motor output, has demonstrated potential as a technique for promoting the recovery of motor functioning in neurological conditions characterised by motor disturbances, such as Parkinson’s disease (PD). However, the utility of this rehabilitation technique is contingent upon the preservation of MI. Existing evidence suggests that MI is largely preserved in PD. However, previous studies typically analysed global MI measures, thereby overlooking the potential influence of individual differences in symptom presentation on MI. The present study investigated the influence of bradykinesia and tremor severity on MI vividness scores in 44 individuals with mild to moderate idiopathic Parkinson’s. First, test-retest reliability of the KVIQ was demonstrated in 19 participants over a longer time period than in previous studies. Linear mixed effects modelling revealed that imagery modality and the severity of left-body bradykinesia significantly influenced MI vividness ratings. Consistent with previous findings, participants rated visual imagery (VMI) to be more vivid than kinesthetic imagery (KMI). Greater severity of left-side bradykinesia predicted increased vividness of KMI but not VMI, while tremor severity and overall motor symptom severity did not predict either KMI or VMI. These findings may reflect the differential neurophysiology of tremor and bradykinesia. Furthermore, the specificity of the effect to the left-side may reflect enhanced baseline vividness of KMI for the dominant (right) body-side, or increased attention to more effortful left-body movements resulting in enhanced vividness of MI

Putting Like a Pro: The Role of Positive Contagion in Golf Performance and Perception

Many amateur athletes believe that using a professional athlete's equipment can improve their performance. Such equipment can be said to be affected with positive contagion, which refers to the belief of transference of beneficial properties between animate persons/objects to previously neutral objects. In this experiment, positive contagion was induced by telling participants in one group that a putter previously belonged to a professional golfer. The effect of positive contagion was examined for perception and performance in a golf putting task. Individuals who believed they were using the professional golfer's putter perceived the size of the golf hole to be larger than golfers without such a belief and also had better performance, sinking more putts. These results provide empirical support for anecdotes, which allege that using objects with positive contagion can improve performance, and further suggest perception can be modulated by positive contagion

Susceptibility to geometrical visual illusions in Parkinson’s disorder

Parkinson’s disorder (PD) is a common neurodegenerative disorder affecting approximately 1–3% of the population aged 60 years and older. In addition to motor difficulties, PD is also marked by visual disturbances, including depth perception, abnormalities in basal ganglia functioning, and dopamine deficiency. Reduced ability to perceive depth has been linked to an increased risk of falling in this population. The purpose of this paper was to determine whether disturbances in PD patients’ visual processing manifest through atypical performance on visual illusion (VI) tasks. This insight will advance understanding of high-level perception in PD, as well as indicate the role of dopamine deficiency and basal ganglia pathophysiology in VIs susceptibility. Groups of 28 PD patients (Mage = 63.46, SD = 7.55) and 28 neurotypical controls (Mage = 63.18, SD = 9.39) matched on age, general cognitive abilities (memory, numeracy, attention, language), and mood responded to Ebbinghaus, Ponzo, and Müller-Lyer illusions in a computer-based task. Our results revealed no reliable differences in VI susceptibility between PD and neurotypical groups. In the early- to mid-stage of PD, abnormalities of the basal ganglia and dopamine deficiency are unlikely to be involved in top-down processing or depth perception, which are both thought to be related to VI susceptibility. Furthermore, depth-related issues experienced by PD patients (e.g., increased risk for falling) may not be subserved by the same cognitive mechanisms as VIs. Further research is needed to investigate if more explicit presentations of illusory depth are affected in PD, which might help to understand the depth processing deficits in PD