Information for step length adjustment in running

The purpose of this study was to directly test the hypothesis that the tau parameter, as introduced by Lee et al. [Lee, D. N., Lishman, J. R., & Thomson, J. A. (1982). Regulation of gait in long jumping. Journal of Experimental Psychology: Human Perception and Performance, 8, 448-459] and Warren et al. [Warren, W. H., Young, D. S., & Lee, D. N. (1986). Visual control of step length during running over irregular terrain. Journal of Experimental Psychology: Human Perception and Performance, 12, 259-266], is the primary information used to regulate step length in running toward a ground target. Visual information available to research participants performing a facsimile of a long jump approach run was manipulated, and the effects on task performance and running gait were observed. Task performance and running gait were unaffected or minimally affected by (a) a perturbation of the normal optical expansion of the target, (b) elimination of global optical flow - including the focus of expansion, and (c) elimination or severe degradation of visual information about distance from the target as well as running velocity. The findings are inconsistent with notions that time-to-arrival with a ground target while running is predominantly specified optically by (a) local tau, (b) global tau, or (c) a distance/velocity computational strategy. A multisensory tau hypothesis regarding informational support for step length adjustment in running is offered.     

Independence of terminal-link entry rate and immediacy in concurrent chains

In Phase 1, 4 pigeons were trained on a three-component multiple concurrent-chains procedure in which components differed only in terms of relative terminal-link entry rate. The terminal links were variable-interval schedules and were varied across four conditions to produce immediacy ratios of 4:1, 1:4, 2:1, and 1:2. Relative terminal-link entry rate and relative immediacy had additive and independent effects on initial-link response allocation, and the data were well-described by a generalized-matching model. Regression analyses showed that allowing sensitivity to immediacy to vary across components produced only trivial increases in variance accounted for. Phase 2 used a three-component concurrent-schedules procedure in which the schedules were the same as the initial links of Phase 1. Across two conditions, the relative reinforcer magnitude was varied. Sensitivity to relative reinforcer rate was independent of relative magnitude, confirming results of prior studies. Sensitivity to relative reinforcer rate in Phase 2 did not vary systematically across subjects compared to sensitivity to relative entry rate in Phase 1, and regression analyses confirmed again that only small increases in variance accounted for were obtained when sensitivities were estimated independently compared with a single estimate for both phases. Overall, the data suggest that conditioned and primary reinforcers have functionally equivalent effects on choice and support the independence of relative terminal-link entry rate and immediacy as determiners of response allocation. These results are consistent with current models for concurrent chains, including Grace's (1994) contextual choice model and Mazur's (2001) hyperbolic value-added model.     

A temporal model of level-invariant, tone-in-noise detection

Level-invariant detection refers to findings that thresholds in tone-in-noise detection are unaffected by roving-level procedures that degrade energy cues. Such data are inconsistent with ideas that detection is based on the energy passed by an auditory filter. A hypothesis that detection is based on a level-invariant temporal cue is advanced. Simulations of a leaky-integrator model, consisting of a bandpass filter, half-wave rectification, and a lowpass filter, account for thresholds in band-widening experiments. The decision variable is calculated from the discrete Fourier transform of the leaky-integrator output. A counterintuitive finding is the apparent disassociation of the phenomenon of critical bands estimated from band-widening experiments and the theory of auditory filters. Physiological plausibility is demonstrated by showing that a leaky integrator describes the discharge cadence of primary afferents for tone-in-noise stimuli as well as for complex periodic sounds.     

The role of oculomotor information in the learning of sequential aiming movements

With their eyes initially on either the home, midline, or final end position, 30 participants practiced a 2-target aiming movement. After 120 acquisition trials, participants performed a retention test and were then transferred to each of the other 2 eye conditions. During acquisition, all groups improved over practice, but the home group showed the greatest improvement. The temporal improvement was most pronounced in the times spent after peak velocity. Retention and transfer tests indicated that participants performed best under eye-movement conditions that were the same as the 1 they had practiced in. There was also positive transfer of training between conditions in which the oculomotor information was similar. Thus, to optimize learning, one should practice under the same afferent and oculomotor conditions that will be required for the final performance.     

Performance on a simple reaction time task while sleep deprived

Divergent results have been reported on the effect of a night's sleep loss on performance of a single monotonous task. The present experiment examined the effect that partial sleep deprivation had on 10 participants' performance on a simple reaction time task requiring low responding for 120 min. compared to performance on the same task when well rested. Participants missed significantly more signals and had slower reaction times when sleep deprived. Reaction times increased with time when participants were both sleep deprived and rested, but the number of misses did not significantly change over time. Reaction time was significantly correlated with subjective ratings of sleepiness and heart rate in both conditions. EEG and heart-rate variability measures did not correlate significantly with reaction time. Misses correlated significantly with subjective ratings and heart rate but only in the rested condition.     

The family covenant and genetic testing

The physician-patient relationship has changed over the last several decades, requiring a systematic reevaluation of the competing demands of patients, physicians, and families. In the era of genetic testing, using a model of patient care known as the family covenant may prove effective in accounting for these demands. The family covenant articulates the roles of the physician, patient, and the family prior to genetic testing, as the participants consensually define them. The initial argument defines the boundaries of autonomy and benefit for all participating family members. The physician may then serve as a facilitator in the relationship, working with all parties in resolving potential conflicts regarding genetic information. The family covenant promotes a fuller discussion of the competing ethical claims that may come to bear after genetic test results are received.     

Effects of escape to alone versus escape to enriched environments on adaptive and aberrant behavior

Escape-maintained aberrant behavior may be influenced by two outcomes: (a) a break from the activity and (b) subsequent access to preferred activities. To assess this hypothesis, a treatment was developed that analyzed response allocation across two break options: break alone and break with access to preferred social activities. The break with preferred activities decreased aberrant behavior and increased appropriate behavior.     

AN EVALUATION OF LABELING-THEN-DOING WITH MODERATELY HANDICAPPED PERSONS: ACQUISITION AND GENERALIZATION WITH COMPLEX TASKS

We conducted two experiments in which moderately mentally retarded persons were trained first to label and then to enter characters into a computer, calculator, or checkbook (label-then-do) within a multiple baseline design. In Experiment 1, 5 young adults were trained to enter statistical programs into computers in an office setting. Following training, all subjects' use of verbal labels and key-entry skills generalized across tasks (programs) and settings (offices and computer terminals). In Experiment 2, 3 junior high school students were trained with self-labeling procedures to complete a key-entry task and to balance a checkbook. The performance of all students generalized across tasks and settings, and the use of labels generalized for 2 of the students. Results are discussed relative to mediated generalization and to establishing verbal control over behavior.     

USE OF NEGATIVE REINFORCEMENT IN THE TREATMENT OF SELF-INJURIOUS BEHAVIOR

Behavioral assessment procedures were used to determine the maintaining conditions of self-injury exhibited by 2 children with severe multiple handicaps. For both children, negative reinforcement (escape from grooming activities) was determined to be the maintaining reinforcer for self-injury (hand/arm biting) within an alternating treatments design. The treatment packages involved the use of negative reinforcement (brief escape from grooming activities) contingent upon a behavior that was incompatible with self-injury (reaching and pressing a microswitch that activated a prerecorded message of “stop”). Treatment was evaluated with a reversal design for 1 child and with a multiple baseline across grooming activities for the 2nd child. The treatment led to a marked decrease in self-injury for both children. At follow-up, high rates of self-injury were reported for the 1st child, but low rates of self-injury and an increase in task-related appropriate behavior were observed for the 2nd child.     

Differentiating ego functions of borderline and narcissistic personalities

This study investigated differences in ego functions of borderline and narcissistic personality disorders through examining responses to Rorschach structural and content variables. Reality testing, thought process, affective regulation, impulse control, and the defenses of splitting and grandiosity were examined from Rorschach protocols of 50 borderlines and 26 narcissists. The borderlines produced greater distortion in reality testing, p less than .05; the narcissists produced more insidious thought process disturbance, p less than .05; and higher functioning groups demonstrated greater control of impulses, p less than .05. Borderlines in this sample demonstrated more affective constriction than the narcissists and used more splitting, p less than .05; narcissists used more grandiosity, p less than .05. Implications of this study are (a) ego functions mature inconsistently, (b) affective responsivity influences ego disorganization, and (c) level of functioning and IQ are related to the production of Rorschach variables.