Pre-Motor and Motor Reaction Time Differences Associated with Stretching of the Hamstring Muscles

Pre-motor and motor RT scores were obtained from 24 male Ss using a knee flexion task. It was predicted that an increased arousal state due to proprioceptive feedback from stretched hamstring muscles would shorten pre-motor RT while motor RT would shorten because of changes in muscle tension development due to changes in the series elastic and/or contractile components of the muscle tissue. A finger RT task was also included in order to determine whether other factors not related to changes in the stretch of the hamstring muscles were operative. Motor RT decreased with increased muscle stretch and constituted 46% of leg RT. Pre-motor RT as well as finger RT increased rather than decreased with increased muscle stretch. No relationship was found between pre-motor and motor RT indicating that lags in CNS processing are independent of lags associated with the rate of muscular tension development.     

Intentional action first

The paper motivates a novel research programme in the philosophy of action parallel to the ‘Knowledge First’ programme in epistemology. It is argued that much of the grounds for abandoning the quest for a reductive analysis of knowledge in favour of the Knowledge First alternative is mirrored in the case of intentional action, inviting the hypothesis that intentional action is also, like knowledge, metaphysically basic. The paper goes on to demonstrate the sort of explanatory contribution that intentional action can make once it is no longer taken to be a target for reductive analysis, in explaining other, non-intentional kinds of action and voluntariness.     

Is the principle of minimization of secondary moments validated during various fingertip force production conditions?

During the application of fingertip forces with simultaneous flexion of the four fingers, namely index, middle, ring, and little fingers, a stable force sharing among fingers is adopted. Several studies have hypothesized that this stable force sharing is established to minimize unnecessary rotational moments (different from the main flexion moments). This principle labeled "minimization of secondary moments" is presented in the literature as a principle used by the central nervous system to solve musculoskeletal redundancy. However, this principle has only been tested with one solicited degree of freedom and in one finger posture. Our study tests this principle with various degrees of freedom solicited as secondary moments and in two different finger postures. Participants (n=6) were asked to apply a downward vertical force using their four fingers with the forearm placed in two different configurations: a "horizontal" condition (involving flexion/extension and pronation/supination at the wrist joint) and a "vertical" condition (involving flexion/extension and radial/ulnar deviation at the wrist joint). Additionally, two finger postures were tested in each forearm configuration: in the first, the distal inter-phalangeal joints (DIP) were extended and the proximal inter-phalangeal joints (PIP) highly flexed. In the second finger posture, both DIP and PIP joints were flexed. The resultant four-finger force and the relative involvement of each finger in the resultant four-finger force (force sharing) were analyzed. Results showed that the finger postures did not influence the finger force sharing, showing that the minimization of the secondary moment principle was stable among the finger joint angle configurations. Nonetheless, the relative involvement of each finger was dependent on the secondary degree of freedom solicited (pronation/supination vs. radial/ulnar). The modifications of the finger force sharing between the "horizontal" and "vertical" conditions were in accordance with the principle of minimization of the secondary moments.     

Recovery Recovered

The most controversial condition that the AGM theory of rational belief change places on belief contraction is the recovery condition. The condition is controversial because of a series of putative counterexamples due (separately) to I. Levi and S. O. Hansson. In this paper we show that the conflicts that Levi and Hansson arrange between AGM contraction and our intuitions about how to give up beliefs are merely apparent. We argue that these conflicts disappear once we attend more closely to the identification of the beliefs contracted away in each counterexample case. Since, on our view, speakers" belief contraction intentions are often more complicated than they may first appear, we are led to develop apparatus for thinking about the communication and identification of those intentions. Our argument refocuses attention on the difficult question of how to apply the AGM theory to particular cases.