Effects of time uncertainty and instructed muscle tension on fractionated reaction time

Abstract: An experiment was conducted to examine the effects of time uncertainty and instructed muscle tension on the reaction time of elbow flexion. Twenty-two right-handed subjects were asked to respond to an audio stimulus by flexing their right elbow under four conditions (2 time uncertainty × 2 instructed muscle tension). Electromyograms (EMGs) were recorded from the biceps and triceps on the subject's right side. Reaction time was divided into premotor time and motor time, based on the difference between the EMG and elbow flexion response. Analysis of reaction time showed that the effects of time uncertainty and instructed muscle tension were additive. Time uncertainty affected premotor time only, and instructed muscle tension affected motor time only. These results are discussed in terms of the assumption that premotor time is a reflection of the central nervous system and motor time is a reflection to the peripheral muscle system.     

Evidence of the origin of specific spontaneous head turns during intertrial intervals

Direction and the frequency of spontaneous head movements during the ITIs following forward and backward paired trials were compared to an acquisition of a conditioned orienting (alpha) response directed to the side of the tone source. The head movements were analyzed from video recordings using classification of head turns to preferred and to nonpreferred directions. The results showed a significant increase in the alpha responses during the forward paired conditioning to the preferred direction and rapid extinction during the subsequent backward conditioning sessions. Spontaneous head movements during the ITIs increased to the same preferred direction as the conditioned alpha responses. The results of this experiment suggest that the response initially elicited by the CS can later appear as “spontaneous,” instrumental behavior, the form and the nature of which is determined by the characteristics of the conditioned alpha response developing as a result of classical conditioning.     

Models for measurement,precision, and the nondichotomization of graded responses

It is common in educational, psychological, and social measurement in general, to collect data in the form of graded responses and then to combine adjacent categories. It has been argued that because the division of the continuum into categories is arbitrary, any model used for analyzing graded responses should accommodate such action. Specifically, Jansen and Roskam (1986) enunciate ajoining assumption which specifies that if two categoriesj andk are combined to form categoryh, then the probability of a response inh should equal the sum of the probabilities of responses inj andk. As a result, they question the use of the Rasch model for graded responses which explicitly prohibits the combining of categories after the data are collected except in more or less degenerate cases. However, the Rasch model is derived from requirements of invariance of comparisons of entities with respect to different instruments, which might include different partitions of the continuum, and is consistent with fundamental measurement. Therefore, there is a strong case that the mathematical implication of the Rasch model should be studied further in order to understand how and why it conflicts with the joining assumption. This paper pursues the mathematics of the Rasch model and establishes, through a special case when the sizes of the categories are equal and when the model is expressed in the multiplicative metric, that its probability distribution reflects the precision with which the data are collected, and that if a pair of categories is collapsed after the data are collected, it no longer reflects the original precision. As a consequence, and not because of a qualitative change in the variable, the joining assumption is destroyed when categories are combined. Implications of the choice between a model which satisfies the joining assumption or one which reflects on the precision of the data collection considered are discussed.     

Departure from normal assumptions: A promise for future psychometrics with substantive mathematical modeling

Normal assumptions have been used in many psychometric methods, to the extent that most researchers do not even question their adequacy. With the rapid advancement of computer technologies in recent years, psychometrics has extended its territory to include intensive cognitive diagnosis, etcetera, and substantive mathematical modeling ha become essential. As a natural consequence, it is time to consider departure from normal assumptions seriously. As examples of models which are not based on normality or its approximation, the logistic positive exponent family of models is discussed. These models include the item task complexity as the third parameter, which determines the single principle of ordering individuals on the ability scale.     

Conditional discrimination in mentally retarded adults: the development of generalized skills.

The development of generalized conditional discrimination skills was examined in adults with retardation. Two subjects with histories of failure to acquire arbitrary matching under trial-and-error procedures were successful under procedures that trained one or more prerequisite skills. The successive discrimination between the sample stimuli was established by training the subjects to name the stimuli. The simultaneous discrimination between the comparison stimuli was established using either (a) standard simple discrimination training with reversals or (b) a procedure in which each of the two sample-comparison relations in the conditional discrimination was presented in blocks of trials, with the size of the blocks decreasing gradually until sample presentation was randomized. The amount of prerequisite training required varied across subjects and across successive conditional discriminations. After acquiring either two or three conditional discriminations with component training, both subjects learned new conditional discriminations under trial-and-error procedures. In general, each successive conditional discrimination was acquired more rapidly. Tests showed that conditional responding had become a generalized skill. Symmetry was shown for almost all trained relations. Symmetry trial samples were ultimately named the same as the stimuli to which they were related in training.     

The treatment of muscle tics with dissimilar competing response practice

Prior research has shown that muscle tics can be suppressed by the performance of a competing response contingent on the occurrence of the muscle tics. In an effort to determine whether the topography of the competing response was important to the muscle tic suppressing effects of contingent competing response practice, we evaluated the effects of a competing response that was topographically dissimilar to the muscle tic. Three subjects engaged in dissimilar competing responses contingent on the occurrence of a muscle tic; 2 of these subjects subsequently engaged in similar competing response practice. The results showed a decrease in objective measures of muscle tic frequency with the introduction of dissimilar competing response practice for each subject; subsequent exposure to similar competing response practice for 2 subjects resulted in no additional decrement in the level of muscle tics. These results suggest that the topography of the competing response may not be crucial for the suppression of muscle tics. Discrepancies between the objective measures of muscle tics and self-recorded measures are noted and discussed.     

The effect of question type on resistance to misinformation about present and absent details

The typical misinformation effect shows that accuracy is lower for details about which people received misleading compared to non-misleading (control) information. In two experiments, we examined the misinformation effect for non-witnessed details (i.e., absent). Three question types introduced control, misleading, and absent details (closed, closed-detailed, and open questions) about a mock burglary video. On this misinformation test, participants' reports of absent details were less accurate than control details only when they were introduced using open questions. Misinformation effects in a subsequent recognition test were present for misleading details in both experiments, but for absent details only in Experiment 2. Experiment 2 also revealed that participants who avoided answering open questions containing misleading and absent details had more accurate memories for these details on the subsequent recognition test than participants who answered these questions. In both experiments, confidence was lowest for absent details. Implications for theory and practice are discussed.     

Developmental stuttering and the role of the supplementary motor cortex

Developmental stuttering is a frequent neurodevelopmental disorder with a complex neurobiological basis. Robust neural markers of stuttering include imbalanced activity of speech and motor related brain regions, and their impaired structural connectivity. The dynamic interaction of cortical regions is regulated by the cortico-basal ganglia-thalamo-cortical system with the supplementary motor area constituting a crucial cortical site. The SMA integrates information from different neural circuits, and manages information about motor programs such as self-initiated movements, motor sequences, and motor learning. Abnormal functioning of SMA is increasingly reported in stuttering, and has been recently indicated as an additional “neural marker” of DS: anatomical and functional data have documented abnormal structure and activity of the SMA, especially in motor and speech networks. Its connectivity is often impaired, especially when considering networks of the left hemisphere. Compatibly, recent data suggest that, in DS, SMA is part of a poorly synchronized neural network, thus resulting in a likely substrate for the appearance of DS symptoms. However, as evident when considering neural models of stuttering, the role of SMA has not been fully clarified. Herein, the available evidence is reviewed, which highlights the role of the SMA in DS as a neural “hub”, receiving and conveying altered information, thus “gating” the release of correct or abnormal motor plans.     

Ipsilesional Arm Aiming Movements After Stroke: Influence of the Degree of Contralesional Impairment

The authors examined the effects of the degree of impairment of the contralesional upper limb and the side of the hemispheric damage on ipsilesional upper limb performance in chronic stroke individuals. Right- and left-side stroke resulting in mild-to-severe impairment and healthy participants took part in simple and choice reaction time tasks involving aiming movements. The stroke individuals performed the aiming movements with the ipsilesional upper limb using a digitizing tablet to ipsi- or contralateral targets presented in a monitor. The global performance of the group with severe right hemispheric damage was worse than that of the other groups, indicating that the side of hemispheric damage and degree of motor impairment can adversely affect aiming movement performance.     

I Spy With My Dominant Eye

The authors investigated how visual information from the nondominant and dominant eyes are utilized to control ongoing dominant hand movements. Across 2 experiments, participants performed upper-limb pointing movements to a stationary target or an imperceptibly shifted target under monocular-dominant, monocular-nondominant, and binocular viewing conditions. Under monocular-dominant viewing conditions, participants exhibited better endpoint precision and accuracy. On target jump trials, participants spent more time after peak limb velocity and significantly altered their trajectories toward the new target location only when visual information from the dominant eye was available. Overall, the results suggest that the online visuomotor control processes that typically take place under binocular viewing conditions are significantly influenced by input from the dominant eye.