Variation of Isometric Response Force in the Rat

Hungry, unrestrained rats (N = 7) were rewarded for pressing a response beam in excess of 11 different force requirements. Changes in peak force production as a function of peak force requirement were examined by analyses of the first four moments of distributions of peak response forces: constant error, the within-subject standard deviation, skewness, and kurtosis. Results were similar to those previously obtained with human subjects: Constant error was positive at low and negative at high force requirements, the within-subject standard deviation increased as a negatively accelerating function of force requirement, and skewness and kurtosis were positive at low force requirements and decreased to negative values at the highest increments. Additional analyses of response kinetics indicated that rats, like humans, meet increasing force requirements by altering the rate of rise of force. The performance similarities suggest that common processes are engaged by the human and rat motor control systems to solve the problem of generating forces that are appropriate to the prevailing environmental constraints.     

Preload and Isometric Force Variability

Two experiments are reported, which examined the relative contributions of preload (resting force level), change of force, and the time taken to achieve the force in determining isometric force variability. The findings showed that change of force is the strongest determiner of peak force variability but that preload and time to peak force have smaller though systematic effects. A formula that predicts peak force variability is proposed, with preload as an additive effect to the ratio between the change of force level and the square root of time to peak force. These findings confirm that these three impulse variables are significant in predicting force variability and that the impact of rate of force on peak force variability is nonlinear.     

On the Relationship Between Peak Force and Peak Force Variability in Isometric Tasks

An experiment is reported documenting the relationship between peak force and peak force variability with a fixed criterion time to peak force for an isometric task requiring activation of the elbow flexors. The results show that maximum peak force increases with increments in time to peak force and that peak force variability increases with increments of peak force in an exponential type function. Furthermore, despite the presence of peak force and time to peak force feedback, subjects systematically shifted time to peak force as a function of the percentage of peak force being produced. This temporal modulation changes the percentage of peak force represented by any given peak force criterion. When peak force is made proportional to the degree of departure from the criterion time to peak force, a linear relationship is found between peak force and peak force variability. These findings suggest that time to peak force and rate of force production are parameters that influence veridical estimates of the force variability function.     

The Effects of Force and Direction Uncertainty on Choice Reaction Time in an Isometric Force Production Task

The two experiments reported examined the temporal organization of force and direction motor-programming processes in a step-input tracking type task. Both experiments observed a reduction in reaction time in the direction-uncertain conditions compared to the direction-certain ones. Thus it seems as though the direction decision does not have to precede the selection of the proper amount of force. Experiment 2 observed an underadditive interaction between levels of direction uncertainty (certain or uncertain) and levels of force uncertainty (certain or uncertain). This interaction was interpreted as support for a parallel organization of the processes responsible for the programming of force and direction and thus, strongly supports the parallel model of programming recently proposed by Klapp (1977a, b).     

Directional Variability of the Isometric Force Vector Produced by the Human Hand in Multijoint Planar Tasks

Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. The subjects applied isometric forces to a handle and the authors compared within-trial variability when force is produced in different directions. The standard deviation of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the standard deviation of the force perpendicular to the instructed direction. In contrast, the standard deviation of the angle of force production decreased with increased force level. In the 4 (of 8) instructed force directions where the endpoint force was generated due to a joint torque in only 1 joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the 2 force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving 2 joints, although this statement needs to be supported by direct studies of muscle activation in the future.     

Effects of Response Probability on Response Force in Simple RT

Response force (RF) was measured in a simple reaction time (RT) experiment varying response uncertainty by cuing the probability of the response on each trial. In all cases, RF decreased as response probability increased. The dependence of RF on response probability was insensitive to foreperiod length and to the use of loud auditory response signals, although the dependence of RT on response probability was sensitive to both of these manipulations. In combination with previous findings, these results provide evidence that RT and RF can be dissociated. We describe an extension of Naatanen's readiness model that can account for the effects of response probability on RF and RT. According to this model, the distance between motor activation and a threshold for action is relatively large when subjects are unprepared, and a large increment is needed to exceed this threshold, resulting in slow but foreceful responses. A possible neurophysiological implementation of this model is suggested.     

Muscle Damaging Exercise Affects Isometric Force Fluctuation as well as Intraindividual Variability of Cognitive Function

Healthy untrained men (N = 11) were asked to perform 10 series of 12 repetitions of knee eccentric extension (EE) at 160° per second. Quadriceps muscle torques evoked by electrical stimulation at 20 Hz (P20) and 100 Hz (P100), maximal voluntary isometric contraction torque (MVC), maximal isokinetic concentric torque (IT) at 30° per second, voluntary activation index (VA), simple reaction time (RTs), complex reaction time (RTc), and torque variability at 30% of MVC were measured before EE, immediately after EE, and 60 min and 24 hr after EE. MVC, IT, P20, P100, and VA decreased significantly after EE and remained depressed 24 hr later. Torque variability increased significantly after EE. Average RTs and RTc did not change after EE, whereas intraindividual variability in RTs and RTc increased significantly after EE.     

Effect of Injected Adrenalin on an Avoidance Response in the Rat

It was hypothesized that slight modifications in word association test (WAT) instructions would have no discernable effect on the responses of college students, but would produce significantly different response hierarchies generated by young children. Seventy-five adults and 375 children gave WAT responses to 32 stimulus words. One-third of the Ss, at each of six grade levels, was given standard WAT instructions; one-third was given a practice session with 10 additional words; and the remainder were instructed to respond to stimulus words with the “first thing” that came to mind. Although the different instructional sets had no discernable effect on the adult Ss, they had a significant effect (ps < .05) upon the number of (a) multiple-word and nonword responses, (b) paradigmatic responses, and (c) idiosyncratic responses produced by the children. These differences suggest that caution be used in the interpretation of WAT responses provided by young Ss.     

Role of Glucocorticoids on Rat Brain Metallothionein-I and -III Response to Stress

The metallothionein (MT) gene family consists of four members (MT-I through -IV) that are tightly regulated during development. Whereas MT-I and MT-II are widely expressed isoforms, MT-III has been found to be mainly expressed in the central nervous system in adult animals, and is the only isoform that inhibits survival and neurite formation of cortical neurons in vitro. A number of models of brain injury have been shown to affect MT-III mRNA levels, which has been suggested to be related to the putative neurotrophic role of this protein. However, a stress response will presumably be associated to the brain injury which could, in turn, drive MT-III regulation. In the present report the effect of a classical stress model, immobilization stress, on brain MT regulation has been studied in rats. MT-I+II protein levels were measured by radioimmunoassay in up to eight brain areas and, as expected, it was found that stress increased selectively MT-I+II levels. Adrenalectomy (ADX) had a general decreasing effect on basal MT-I+II levels; however, ADX blunted the MT-I+II response to stress in cerebellum and presumably in frontal cortex and medulla plus pons but not in the hypothalamus. MT-I mRNA measurements were in accordance with the MT-I+II protein levels in the brain areas studied. In contrast to MT-I mRNA, MT-III mRNA levels of brain cortex tended to decrease during stress, although this effect was not statistically significant. ADX also tended to decrease basal MT-III mRNA levels. Northern blot assays of pooled mRNAs suggested similar differential regulation of these two brain MT isoforms in the cerebellum. These results indicate that glucocorticoids mediate brain MT-I+II response to stress in some but not all brain areas, that a role of these hormones is likely also for MT-III, and that the regulation of MT isoforms differs substantially in the brain.     

The Selected Response Procedure: A Variation on Appelbaum's Altered Atmosphere Procedure for the Rorschach

This article introduces the Selected Response Procedure, which is a supplementary technique for expanding the scope of the Rorschach test. The procedure is conducted as follows: After the standard administration of the Rorschach test, patients are asked to look through all of the cards a second time and select one more response from any card of their choice. A rationale for this procedure is developed through a comparison to another supplementary Rorschach technique, the Altered Atmosphere Procedure. The importance of understanding the selected response within a theoretical framework, as well as the clinical context of each selected response, is highlighted by a clinical example using object relations theory. Finally, a number of didactic questions are offered as potential ways to query the possible meaning of selected responses.     

The Visibility Curve of the White Rat as Determined by the Electrical Retinal Response to Lights of Different Wave-Lengths

The relative influence of three degrees of instance contiguity (mixed, mixed-by-dimension, and nonmixed) and two orders of presentation (simple-to-complex, and complex-to-simple) on subject's proficiency at identifying nine concepts was examined. The concepts could be classified along one of three relevant dimensions (object, form, and number) and varied in difficulty so that object concepts were easier than forms, and forms were easier than numbers.

Forty-eight college students served as subjects, and were presented 18 positive instances of each concept in one of six treatment combinations. Performance across three trial blocks (each block encompassing concept instances relevant to one dimension) was examined in conjunction with contiguity and presentation order.

Analysis of variance revealed significance for order (p < .001), trials (p < .025), Trials x order (p < .001), and the residual (p < .05). Order differences within each trial block were greatest under nonmixed and least under mixed-by-dimension contiguity conditions. A two-stage mediation hypothesis was advanced to account for these results.     

Prioritizing Sales Force Decision Areas for Productivity Improvements using a Core Sales Response Function

The time and budgets that managers can devote to enhancing sales force productivity are limited, so sales managers must decide where it is worthwhile to invest in productivity improvements—to improve salespeople’s current effort allocation, realign territories, enhance sales force sizing, or provide more training. To prioritize these alternatives, management must assess the outcomes of investments on the basis of a common metric—profit. This paper proposes to estimate a core sales response function that allows for quantifying the profits derived from each possible action and demonstrates the benefits of this approach through an actual case study.     

The Influence of Competition on the Efficiency of an Isometric Muscle Contraction

36 male Ss from collegiate intramural athletic teams were asked to maintain 50% of their maximum voluntary contraction on an iso-metric handle as long as possible. Ss were divided into 2 groups. One group performed individually while the other group, in teams of 3 Ss each, competed for a team prize. During the session, the active muscle was continuously monitored by EMG. The introduction of the motivational factors of competition and team presence did not increase the mean endurance time, but muscle EMG activity was significantly increased when additional motivational factors were introduced. It was concluded that team presence and competition are better described as stress factors which reduce the efficiency of the muscles. The reduction of efficiency is explained both in terms of increased activity of the antagonistic muscles and an increase in S’s general arousal level.     

Conditional Reactions in the Rat

To assess the effects of the presence of the experimenter (E) and/or modelrewarder (MR), elementary school children observed a model emit specific sequences on a button pressing task in two separate experiments (N = 50 and N = 80). The first design was a 2 × 2 factorial involving the presence-absence of the E/MR and model reward vs. model no-consequences; the second design was a 4 × 2 factorial with all possible combinations of presence-absence of the E and/or MR, and model reward vs. model no-consequences. It was found that model reward increased imitation only in the condition in which the E was present and the MR was absent.     

Depth Discrimination in the Rat

Abstract

     

Drug Abuse in the Sales Force

Drug abuse in the workplace is a national problem of frightening proportions and there is no reason to suspect that the nations's sales forces should be immune. This study examines the problem of sales force drug abuse and reports the findings of a nationwide survey of field sales managers concerning the extent of drug abuse in the nation's sales forces, the methods of dealing with the problem, and factors related to drug abuse problems in the sales force. Implications for sales managers, sales management educators and trainers, and researchers in the field of sales and sales management are also discussed.     

Organizational Commitment in the Sales Force

Abstract

Research concerning the determinants of salesperson performance has emphasized expectancy theory. While results of such studies have added greatly to our understanding of sales force behavior, the expectancy theory approach has been questioned concerning its ability to explain consistency in behavior. A potential alternative explanation for behavioral consistency lies in the concept of organizational commitment. This paper explores organizational commitment in a sales setting, discussing research findings from other disciplines and providing a conceptual framework to help guide future research in sales management.