Modifying an underlying component of perceived arm length: adaptation of tactile location induced by spatial discordance

In four experiments we examined the adaptation and aftereffect that resulted from a treatment yielding tactile/kinesthetic length discordance between the arms. Perceived discordance diminished with trials and tended to zero. Subsequent visual/tactile cross-modal judgments of distance showed the aftereffect to be a change in the perceived location of an unseen probed spot on each hand with respect to the location of a truly coincident visual marker. This occurred toward the body for the probed spot on one arm and away from the body on the other. There were three other main findings: (a) Arm movement was not a necessary condition for adaptation or aftereffect; (b) with intrinsic length information about the right arm present, but touch information from the right index finger absent during treatment, adaptation and aftereffect were abolished; (c) aftereffects of tactile location that were manifest at the hand and wrist tended to zero when a point close to the elbow was tested with a cross-modal procedure. The experiments provide evidence that the mapping of the tactile sheet onto an internal length domain had been modified by the treatment. The sensory consequences of the treatment led many subjects to report spontaneously that their arms felt to be of different lengths.     

A developmental study of schedule-induced polydipsia in the rat

Rats 30, 60, 90, and 120 days of age were fed 105 45-mg food pellets on a noncontingent VT 70-sec schedule during 14 daily 2-hr sessions. Every animal became polydipsic on this schedule when compared with a schedule in which 105 pellets were presented at the beginning of the session. Mean polydipsic ratios (schedule intake/control intake) ranged from 2.9–5.4. Water intakes (milliliters per 100g body weight) did not differ during the last five sessions as a function of age. The results are discussed with respect to the generality of the class of adjunctive behaviors.     

Hierarchical control of rapid movement sequences

Are movement sequences executed in a hierarchically controlled fashion? We first state explicitly what such control would entail, and we observe that if a movement sequence is planned hierarchically, that does not imply that its execution is hierarchical. To find evidence for hierarchically controlled execution, we require subjects to perform memorized sequences of finger responses like those used in playing the piano. The error data we obtain are consistent with a hierarchical planning as well as execution model, but the interresponse-time data provide strong support for a hierarchical execution model. We consider three alternatives to the hierarchical execution model and reject them. We also consider the implications of our results for the role of timing in motor programs, the characteristics of motor buffers, and the relations between memory for symbolic and motor information.     

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Knowledge, Technology &; Policy -     

Stressed organizations and organizational stressors: A systemic analysis of workplace injury

The experiences of five injured workers from one workplace which had been identified as having a very poor workers' compensation claims experience were analyzed using a systemic theory framework. It was predicted that the fundamental stress-producing conflict between safety and profit that exists in industry between workers and their employers is exacerbated when a worker is injured; furthermore, the degree of stress experienced by both the injured worker and the employer is related to the impact of the injury on the organization and on the productivity of the workplace. The increased stress in both the injured worker and the employer results in increased rigidity in responding to the change or threat in the organization caused by workplace injury. A systemic approach to rehabilitation was recommended in which the employer as well as the injured worker were viewed as clients who required varying levels of support and intervention in managing workplace injury.     

Accuracy in judgments of aggressiveness

Perceivers are both accurate and biased in their understanding of others. Past research has distinguished between three types of accuracy: generalized accuracy, a perceiver's accuracy about how a target interacts with others in general; perceiver accuracy, a perceiver's view of others corresponding with how the perceiver is treated by others in general; and dyadic accuracy, a perceiver's accuracy about a target when interacting with that target. Researchers have proposed that there should be more dyadic than other forms of accuracy among well-acquainted individuals because of the pragmatic utility of forecasting the behavior of interaction partners. We examined behavioral aggression among well-acquainted peers. A total of 116 9-year-old boys rated how aggressive their classmates were toward other classmates. Subsequently, 11 groups of 6 boys each interacted in play groups, during which observations of aggression were made. Analyses indicated strong generalized accuracy yet little dyadic and perceiver accuracy.     

Minimal Requirements for the Emergence of Learned Signaling

The emergence of signaling systems has been observed in numerous experimental and real‐world contexts, but there is no consensus on which (if any) shared mechanisms underlie such phenomena. A number of explanatory mechanisms have been proposed within several disciplines, all of which have been instantiated as credible working models. However, they are usually framed as being mutually incompatible. Using an exemplar‐based framework, we replicate these models in a minimal configuration which allows us to directly compare them. This reveals that the development of optimal signaling is driven by similar mechanisms in each model, which leads us to propose three requirements for the emergence of conventional signaling. These are the creation and transmission of referential information, a systemic bias against ambiguity, and finally some form of information loss. Considering this, we then discuss some implications for theoretical and experimental approaches to the emergence of learned communication.