On optimal smoothing and derivative estimation from noisy displacement data in biomechanics

Estimating derivatives from noisy displacement data is a notoriously ill-posed problem in signal processing and biomechanics. Following the work of Wood and Jennings (1978) and Hatze (1979, 1981), the present paper describes the use of optimally regularized, natural quintic splines for estimating smoothed positions, velocities, and accelerations from equidistantly sampled, noisy position measurements. It appears that the nature of the boundary conditions of the data is of some importance, since various algorithms used hitherto result in artefacts throughout the data if the true derivatives at the record ends differ significantly from zero. Natural quintic splines do not suffer from this disadvantage below the third derivative.The ill-posed character of movement analysis has some interesting implications for movement synthesis and optimization, similar to the indeterminacy of muscular co-contraction from merely external, biomechanical measurements.     

A test of the self-perception explanation of the effects of rewards on intrinsic interest

An experiment was conducted to test the proposition that rewards undermine or enhance intrinsic interest in a task to the extent that individuals interpret their behavior as being motivated by the reward. It was predicted that when subjects were denied the opportunity to develop and confirm this attribution, rewards would not produce an undermining effect, but rather would enhance dispositions and behavior. Subjects were recruited to evaluate a new sugar-free soft drink. Two levels of incentives (reward-no reward), two levels of examination (opportunity-no opportunity), and three levels of outcome (good-neutral-poor) were employed. The results support the prediction that an incentive's effect depends on the examination opportunity. In the examination condition, rewarded subjects attributed their behavior more to external factors than did unrewarded subjects, but gave more negative product evaluations only after tasting it. In the no examination condition, there were no differences in the attributions made by rewarded and unrewarded subjects, and rewarded subjects were more positively disposed toward the product both before and after tasting it. These results are explained as a consequence of two properties of rewards, enhancement through reinforcement and undermining through discounting, and of hypothesis-testing processes.     

Slow brain potentials in the CNV-paradigm

Slow brain potentials were recorded during the foreperiod of a reaction time task, and the effects of instructions governing the trade-off between speed and accuracy were investigated. One brain potential, a slow negative shift preceding S₂, was largely attenuated under accuracy instructions. It is suggested that this shift is dependent on a motor response and that its amplitude reflects the level of motor preparation. Two other brain potentials, a slow positive and a slow negative wave, seem to depend on the psychological properties of S₁. Enhanced amplitudes were found, when S₁ provides information, besides its warning function.     

Treatment of obsessive-compulsive patients: The contribution of self-instructional training to the effectiveness of exposure

Fifteen obsessive-compulsive patients were given treatment consisting of ten sessions of gradual exposure in vivo. For half of the patients gradual exposure in vivo was preceded by self-instructional training.Treatment resulted in significant improvement on anxiety and avoidance scales, Leyton Obsessional Inventory, Self-rating Depression Scale and on ratings for anxious mood and depression. Neither the post-test nor the follow-ups 1 month and 6 months later indicated a difference between the effects of the two conditions. Self-instructional training did not enhance the effectiveness of gradual exposure in vivo.     

Satiation for social reinforcers: The effects of contingency,vicarious experience,and ambiguous situations

The relative satiation effect, an inverse relationship between the frequency of prior social reinforcement (the word “good”) and the later effectiveness of the social reinforcer in controlling behavior, was studied. In Experiment 1, a discrimination task in which social reinforcement was given for correct responses was administered to first- to fourth-grade children (6 to 10 years of age), who had during a preexposure phase performed a preliminary task or observed another child performing. During the preexposure phase, the experimenter delivered frequent or infrequent social reinforcement that was either contingent or noncontingent. Only performers and observers who had experienced frequent noncontingent reinforcement showed the satiation effect during the discrimination task phase. The results were interpreted as inconsistent with J. L. Gewirtz' (Developmental Psychology, 1969, 1, 2–13) social drive formulation but supportive of an informational analysis in which the children are seen as responding appropriately to unambiguous evidence concerning the reliability of contingency information. In Experiment 2, seating arrangements were varied so that information concerning the direction of reinforcement was made ambiguous. Performers were less responsive during the discrimination phase after experiencing frequent noncontingent reinforcement when seated alone or opposite an observer than when seated next to an observer. The results are interpreted as indicating trust of the reliability of the contingency under ambiguous conditions.     

Meditation,personality and arousal

A questionnaire survey of people who had learned a technique of meditation was carried out to assess persistence with practice, perceived effects of meditation practice and subjective experiences during meditation. The results suggested that a significant proportion give up meditating (42.9%) and that the subjective experience of meditation was similar to that of the hypnagogic state. Reported effects of meditation were generally physiological and psychological benefits related to relaxation.A personality questionnaire was also distributed and the results suggested that those attracted to meditation are significantly more neurotic and introverted than the general population but that those who continue with meditation are significantly less neurotic than those who give up their practice.These findings are discussed in terms of regression effects and in relation to a theory of personality and arousal.