Perception, action, and experience: Unraveling the golden braid

A distinction concerning vision-for-action and affordance perception

In this paper, I offer a discussion concerning the conceptual connection between the notion of vision-for-action and the one of affordance perception. I first analyze the notion of vision-for-action. I then analyze a notion usually coupled with it: the notion of affordance perception, the main insights behind which are guiding several current neuroscientific enterprises and the related philosophical speculations. Then, I argue that we should not couple these two notions with a light heart: though these two processes can be, from a theoretical point of view, related, we should be careful in inferring the actual and effective occurrence of the latter in the presence of the former. This will be done by carrying out a conceptual analysis of the experimental evidence coming from the 'Two Visual Systems Model', which is the main reference in the literature on affordance perception and vision-for-action. My point has strong philosophical implications for our view concerning the best interpretation of how vision-for-action really works, and the specific relation it actually entertains with affordance perception.

Longitudinal progression of posterior cortical atrophy over 11 years: Relationship between lesion topology and clinical deficits

Posterior cortical atrophy (PCA) is a rare form of dementia primarily characterized by slowly progressing deterioration of visual processing corresponding to atrophy in the posterior parietal and occipital cortices with less prominent memory loss than are usually seen in other forms of dementia such as Alzheimer's Disease (AD). In the present case report, we describe longitudinal data over a period of 11 years regarding clinical and neuropsychological impairments and their relation to the location and extent of cortical changes related to higher order visual processing in a patient with posterior cortical atrophy. In our patient, visual processing deficits concerning space, motion and object perception emerged at the age of 50 and continued to worsen. By the age of 58, while the perception of contrast, color and figure-ground separation appeared undisturbed the patient exhibited pronounced dorsal- and ventral-related visual deficits, which continued to worsen with age. The patient's MRI scans over the course of the disease revealed increasing circumscribed and bilateral atrophy of the parietal and occipital cortices, with a right-sided predominance. The specific localization of cortical atrophy, the slow progression characterized by visual processing deficits and relatively preserved memory were the main criteria for the diagnosis of posterior cortical atrophy. The case report also highlights the importance of an early extensive neurological and neuropsychological evaluation of visual deficits that occur without the presence of ophthalmological disease.

Through the forest of motor representations

Following neuroscience, and using different labels, several philosophers have addressed the idea of the presence of a single representational mechanism lying in between (visual) perceptual processes and motor processes involved in different functions and useful for shaping suitable action performances: a motor representation (MR). MRs are the naturalized mental antecedents of action. This paper presents a new, non-monolithic view of MRs, according to which, contrarily to the received view, when looking at in between (visual) perceptual processes and motor processes, we find not only a single representational mechanism with different functions, but an ensemble of different sub-representational phenomena, each of which with a different function. This new view is able to avoid several issues emerging from the literature and to address something the literature is silent about, which however turns out to be crucial for a theory of MRs.

Conscious Action/Zombie Action

I argue that the neural realizers of experiences of trying (that is, experiences of directing effort towards the satisfaction of an intention) are not distinct from the neural realizers of actual trying (that is, actual effort directed towards the satisfaction of an intention). I then ask how experiences of trying might relate to the perceptual experiences one has while acting. First, I assess recent zombie action arguments regarding conscious visual experience, and I argue that contrary to what some have claimed, conscious visual experience plays a causal role for action control in some circumstances. Second, I propose a multimodal account of the experience of acting. According to this account, the experience of acting is (at the very least) a temporally extended, co-conscious collection of agentive and perceptual experiences, functionally integrated and structured both by multimodal perceptual processing as well as by what an agent is, at the time, trying to do.

Conscious Control over Action

The extensive involvement of nonconscious processes in human behaviour has led some to suggest that consciousness is much less important for the control of action than we might think. In this article I push against this trend, developing an understanding of conscious control that is sensitive to our best models of overt (that is, bodily) action control. Further, I assess the cogency of various zombie challenges-challenges that seek to demote the importance of conscious control for human agency. I argue that though nonconscious contributions to action control are evidently robust, these challenges are overblown.

Sinistrals are rarely "right": evidence from tool-affordance processing in visual half-field paradigms

Although current neuroscience and behavioral studies provide substantial understanding of tool representations (e.g., the processing of tool-related affordances) in the human brain, most of this knowledge is limited to right-handed individuals with typical organization of cognitive and manual skills. Therefore, any insights from these lines of research may be of little value in rehabilitation of patients with atypical laterality of praxis and/or hand dominance. To fill this gap, we tested perceptual processing of man-made objects in 18 healthy left-handers who were likely to show greater incidence of right-sided or bilateral (atypical) lateralization of functions. In the two experiments reported here, participants performed a tool vs. non-tool categorization task. In Experiment 1, target and distracter objects were presented for 200 ms in the left (LVF) or right (RVF) visual field, followed by 200 ms masks. In Experiment 2, the centrally presented targets were preceded by masked primes of 35 ms duration, again presented in the LVF or RVF. Based on results from both studies, i.e., response times (RTs) to correctly discriminated stimuli irrespective of their category, participants were divided into two groups showing privileged processing in either left (N = 9) or right (N = 9) visual field. In Experiment 1, only individuals with RVF advantage showed significantly faster categorization of tools in their dominant visual field, whereas those with LVF advantage revealed merely a trend toward such an effect. In Experiment 2, when targets were preceded by identical primes, the "atypical" group showed significantly facilitated categorization of non-tools, whereas the "typical" group demonstrated a trend toward faster categorization of tools. These results indicate that in subjects with atypically organized cognitive skills, tool-related processes are not just mirror reversed. Thus, our outcomes call for particular caution in neurorehabilitation directed at left-handed individuals.

Global disorders of consciousness

In recent decades there has been a great deal of interest in global disorders of consciousness, such as the vegetative state, the minimally conscious state, and epileptic absence seizures. Global disorders of consciousness pose significant challenges to consciousness science in that the ordinary pretheoretical criteria for the ascription of consciousness are not easily applied in such contexts, and it is often unclear what kinds of conscious states-if any-patients are in. At the same time, global disorders of consciousness also promise to reveal a great deal about the nature of consciousness and the relationship between consciousness and cognitive and behavioral control. WIREs Cogn Sci 2014, 5:129-138. doi: 10.1002/wcs.1270 CONFLICT OF INTEREST: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.

Concepts about agency constrain beliefs about visual experience

Recent research exploring phenomena such as change blindness, inattentional blindness, attentional blink and repetition blindness has revealed a number of counterintuitive ways in which apparently salient visual stimuli often go unnoticed. In fact, large majorities of subjects sometimes predict that they would detect visual changes that actually are rarely noticed, suggesting that people have strong beliefs about visual experience that are demonstrably incorrect. However, for other kinds of visual metacognition, such as picture memory, people underpredict performance. This paper describes two experiments demonstrating that both these overpredictions of change detection, and underpredictions of visual memory can be linked with intuitions about the visual experience of different kinds of agents. Subjects predicted more visual change detection and poorer visual memory for mechanical representational systems (e.g. computer programs) when these were anthropomorphized using intentional terminology.

Vision for action in toddlers: the posting task

Three experiments examine 18- to 24-month-old (N = 78) toddlers' ability to spatially orient objects by their major axes for insertion into a slot. This is a simplified version of the posting task that is commonly used to measure dorsal stream functioning. The experiments identify marked developmental changes in children's ability to preorient objects for insertion, with 18-month-olds failing completely and 24-month-olds succeeding easily. In marked contrast, 18-month-olds preorient their empty hands for insertion into the same slots. This developmental dissociation between aligning hands and aligning objects to slots suggests that the key developmental change is in action with the goal of object-to-object alignment versus action on an object.

Do we have independent visual streams for perception and action?

The perception-action model proposes that vision-for-perception and vision-for-action are based on anatomically distinct and functionally independent streams within the visual cortex. This idea can account for diverse experimental findings, and has been hugely influential over the past two decades. The model itself comprises a set of core contrasts between the functional properties of the two visual streams. We critically review the evidence for these contrasts, arguing that each of them has either been refuted or found limited empirical support. We suggest that the perception-action model captures some broad patterns of functional localization, but that the specializations of the two streams are relative, not absolute. The ubiquity and extent of inter-stream interactions suggest that we should reject the idea that the ventral and dorsal streams are functionally independent processing pathways.