Viewing objects and planning actions: on the potentiation of grasping behaviours by visual objects

How 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.     

Self and identity in social anxiety disorder

Models of social anxiety (SA) place the self as an organizing and causal center involved in the maintenance of this condition. An integrative conceptual framework for the understanding of the self is used to review the literature on the self in SA. Two main distinctions are emphasized: the self-as-a-subject (I-self) versus self-as-an-object (Me-self), and the evolutionary-based distinction of social rank versus affiliation. We argue that (a) although much progress has been made in understanding the association between SA and Me-self, the association between SA and I-self remains largely unexplored (with the important exception of anxiety-related processes in social situations); and (b) experiences and representations of the self in SA center on social rank. We suggest that in SA, social rank themes constitute the linchpins of identity, defined as the content and structure of the Me-self. We speculate that processes related to low social rank contribute to the focus on representational (Me), rather than experiential (I), self-aspects. Finally, we delineate the ways in which such an understanding may direct and refine the construction of novel, individually tailored, therapeutic approaches.