1,721,061 research outputs found
Viewing objects and planning actions: On the potentiation of grasping behaviours by visual objects
No full textHow do humans interact with tools? Gibson (1979) suggested that humans perceive directly what tools afford in terms of meaningful actions. This "affordances" hypothesis implies that visual objects can potentiate motor responses even in the absence of an intention to act. Here we explore the temporal evolution of motor plans afforded by common objects. We presented objects that have a strong significance for action (pinching and grasping) and objects with no such significance. Two experimental tasks involved participants viewing objects presented on a computer screen. For the first task, they were instructed to respond rapidly to changes in background colour by using an apparatus mimicking precision and power grip responses. For the second task, they received stimulation of their primary motor cortex using transcranial magnetic stimulation (TMS) while passively viewing the objects. Muscular responses (motor evoked potentials: MEPs) were recorded from two intrinsic hand muscles (associated with either a precision or power grip). The data showed an interaction between type of response (or muscle) and type of object, with both reaction time and MEP measures implying the generation of a congruent motor plan in the period immediately after object presentation. The results provide further support for the notion that the physical properties of objects automatically activate specific motor codes, but also demonstrate that this influence is rapid and relatively short lived. © 2011 Elsevier Inc
Are object affordances fully automatic? A case of covert attention
No full textInspired in part by Gibson's (1979) ecological approach to perception, current neurocognitive theories of action suggest that the simple viewing of an object can automatically elicit motor programs for specific acts. However, the degree to which such affordances should be considered truly automatic is unknown. Here we explored the generation of motor plans afforded by pairs of cue objects that were viewed peripherally under different attentional states. Participants focused centrally while attending to just one of two peripheral cue objects that together had a strong significance for pinching, grasping, or both. They were instructed to ignore the objects and instead give power or precision grip responses to subsequent changes in background color. The data showed a significant interaction between type of response and type of object, indicating that object affordances are perceived even in nonfoveal vision. Critically, the generation of affordances was modulated by the locus of attention: Motor preparation was biased toward the attended object when two different categories of object appeared in the same trial, but the generation of affordances was also influenced by unattended stimuli. This finding demonstrates that object-action priming is not completely automatic, instead being constrained by processes of perceptual selection. © 2013 American Psychological Association
Single-pulse TMS related syncopal spell in a healthy subject
No full textLetters to the Editor
Single-pulse TMS related syncopal spell
in a healthy subjec
Unconscious Presentation of Object Affordances Evokes a Negative Compatibility Effect
No full textAccording to Gibson's (1979) theory of “affordances”, the environment is constantly bombarding the viewer with a multitude of possible actions. More recently, it has been suggested that the simple viewing of an object can automatically elicit motor plans for actions towards this object. Research has attributed this phenomenon to the existence of two different neural pathways for processing visual information from objects and implied a distinction between conscious visual perception (meditated by the ventral stream) and unconscious visuomotor control (sub-served by the dorsal stream). This has proved compelling to many researchers, who have further tried to dissociate conscious visual perception from visually guided performance. In the present study, participants formed precision and power grips in response to a central colour stimulus, in order to determine whether these actions could be modulated by the prior subliminal presentation of pinch/grasp affording prime objects. All prime objects were briefly presented for 20 ms, thus making it impossible for participants to consciously identify these. A mask followed the prime's initial onset, after which the target was presented. The time between the onset of the prime and the appearance of the target was, also, varied in order to assess the time course of any priming effects obtained. The results suggest that affordances for relevant actions can also be extracted from objects whose physical properties are far from obvious, and appear inaccessible to consciousness. Furthermore, we provide evidence of a negative compatibility effect under experimental circumstances that have not been described in the literature before, and which rule out many kinds of interaction at a perceptual level
Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence
No full textExtensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision ('pinchable') or whole-hand/power ('graspable') grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450. ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450. ms (but not 150. ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect. © 2013 Elsevier Inc
The truth-telling motor cortex: Response competition in M1 discloses deceptive behaviour
Get PDFNeural circuits associated with response conflict are active during deception. Here we use transcranial magnetic stimulation to examine for the first time whether competing responses in primary motor cortex can be used to detect lies. Participants used their little finger or thumb to respond either truthfully or deceitfully regarding facial familiarity. Motor-evoked-potentials (MEPs) from muscles associated with both digits tracked the development of each motor plan. When preparing to deceive, the MEP of the non-responding digit (i.e. the plan corresponding to the truth) exceeds the MEP of the responding digit (i.e. the lie), whereas a mirror-reversed pattern occurs when telling the truth. This give away response conflict interacts with the time of stimulation during a speeded reaction period. Lies can even activate digit-specific cortical representations when only verbal responses are made. Our findings support neurobiological models which blend cognitive decision-making with motor programming, and suggest a novel index for discriminating between honest and intentionally false facial recognition
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
