Adaptive mechanisms in perceptual-motor coordination: components of prism adaptation

Aftereffect measures of visual shift and proprioceptive shift were obtained for prism exposure conditions in which, at the end of a sagittal pointing movement, most of the arm was visible (concurrent exposure) or only the first finger joint was visible (terminal exposure). Intermediate exposure conditions permitted view of the hand or the first two finger joints. Under the concurrent exposure condition, proprioceptive shift was greater than visual shift but, as view of the pointing hand decreased, the relative magnitude of the two components gradually reversed so that, under the terminal exposure condition, visual shift was greater than proprioceptive shift. These results are discussed in terms of a model of perceptual-motor organization (Redding, Clark, & Wallace, 1985) in which the direction of coordinative linkage between eye-head and hand-head systems determines the locus of discordance and adaptive recalibration.     

Proprioception and the production of adaptation and intermanual transfer to prismatic displacement

Proprioceptive adaptation to prismatic displacement and resultant intermanual transfer were investigated in two experiments. In Experiment 1, magnitude of adaptation and transfer were assessed as a result of the reduction of felt sensation via hypnotic anesthesia in an adapting limb. Such anesthesia reduced the magnitude of adaptation in that limb and resultant transfer in the nonadapting limb to a nonsignificant level. Such was not the case when the adapting limb was nonanesthetic. In Experiment 2, adaptation and transfer magnitude were assessed as the result of anesthetic induction in a nonadapting limb. When this was the case, adaptation was produced in the adapting limb but not in the anesthetized, nonadapting limb. The results of the two experiments generally point to proprioception as being the major source of input to the production of intermanual transfer in a prismatic adaptation task.     

Hypnotic susceptibility and the perception of afterimages and dot stimuli

Three experiments were conducted to determine the relationship between hypnotic susceptibility level and the susceptibility to several perceptual phenomena. Experiment I required subjects to observe an induced afterimage in a light-proofed environment and to report the frequency of direction and color changes. In addition, subjects reported the persistence of the afterimage. Experiment II involved the observation of a black dot against a white background, with frequency of observed movement being the dependent measure. Experiment III was similar to the second experiment except that the stimulus was encompassed by a frame. In Experiments I and II, subjects judged high in hypnotic susceptibility reported perceiving the strongest effect. This phenomenon was virtually eliminated in the third experiment. These results were interpreted as supporting a process whereby subjects judged high in hypnotic susceptibility are better able to selectively attend to relevant cues in a stimulus array during conditions of perceptual impoverishment.     

Visuomotor coordination and intermanual transfer for a proprioceptive reaching task

Two experiments were conducted to determine the role of head constraint, whether present or absent and arm exposure type (terminal or continuous) on the production of intermanual transfer to two types of visual distortion. Experiment 1 investigated intermanual transfer to binocular, lateral prism displacement where the prism base orientation for both eyes was in the same direction. Experiment 2 determined whether intermanual transfer could be produced to squint prism viewing where the prism base orientation for each eye was in an opposite direction (base-out prisms). In both experiments transfer was produced when either head movement during prism exposure was unconstrained or when a terminal arm exposure was employed. Maximal transfer was produced when both of these conditions were employed.     

Temperament, distraction, and learning in toddlerhood

The word- and nonword-learning abilities of toddlers were tested under various conditions of environmental distraction, and evaluated with respect to children's temperamental attentional focus. Thirty-nine children and their mothers visited the lab at child age 21-months, where children were exposed to fast-mapping word-learning trials and nonlinguistic sequential learning trials. It was found that both word- and nonword-learning were adversely affected by the presentation of environmental distractions. But it was also found that the effect of the distractions sometimes depended on children's level of attentional focus. Specifically, children high in attentional focus were less affected by environmental distractions than children low in attentional focus when attempting to learn from a model, whereas children low in attentional focus demonstrated little learning from the model. Translationally, these results may be of use to child health-care providers investigating possible sources of cognitive and language delay.     

Generalization of prism adaptation

Prism exposure produces 2 kinds of adaptive response. Recalibration is ordinary strategic remapping of spatially coded movement commands to rapidly reduce performance error. Realignment is the extraordinary process of transforming spatial maps to bring the origins of coordinate systems into correspondence. Realignment occurs when spatial discordance signals noncorrespondence between spatial maps. In Experiment 1, generalization of recalibration aftereffects from prism exposure to postexposure depended upon the similarity of target pointing limb postures. Realignment aftereffects generalized to the spatial maps involved in exposure. In Experiment 2, the 2 kinds of aftereffects were measured for 3 test positions, one of which was the exposure training position. Recalibration aftereffects generalized nonlinearly, while realignment aftereffects generalized linearly, replicating Bedford (1989, 1993a) using a more familiar prism adaptation paradigm. Recalibration and realignment require methods for distinguishing their relative contribution to prism adaptation.     

Ressentiment and power: On Reginster's The Will to Nothingness

A critical discussion of Bernard Reginster's book The Will to Nothingness. The contribution engages with Reginster's interpretation of Nietzschean ressentiment, arguing that it is an essentially interpersonal attitude in two different senses. It is a response to a social situation of structural deprivation, and it involves an element of antagonism toward those who are better off within this social structure. The contribution then discusses Reginster's claim that modern morality restores the sense of power of the masses by adjusting the goals that they aim to pursue. I argue that this interesting interpretation does not do full justice to the themes of hostility or hatred that permeate the Genealogy of Morals, extending from Nietzsche's discussion of the slave revolt to his treatments of the bad conscience and of ascetic ideals.