Response-rate differences in variable-interval and variable-ratio schedules: An old problem revisited

In Experiment 1, a variable-ratio 10 schedule became, successively, a variable-interval schedule with only the minimum interreinforcement intervals yoked to the variable ratio, or a variable-interval schedule with both interreinforcement intervals and reinforced interresponse times yoked to the variable ratio. Response rates in the variable-interval schedule with both interreinforcement interval and reinforced interresponse time yoking fell between the higher rates maintained by the variable-ratio schedule and the lower rates maintained by the variable-interval schedule with only interreinforcement interval yoking. In Experiment 2, a tandem variable-interval 15-s variable-ratio 5 schedule became a yoked tandem variable-ratio 5 variable-interval x-s schedule, and a tandem variable-interval 30-s variable-ratio 10 schedule became a yoked tandem variable-ratio 10 variable-interval x-s schedule. In the yoked tandem schedules, the minimum interreinforcement intervals in the variable-interval components were those that equated overall interreinforcement times in the two phases. Response rates did not decline in the yoked schedules even when the reinforced interresponse times became longer. Experiment 1 suggests that both reinforced interresponse times and response rate–reinforcement rate correlations determine response-rate differences in variable-ratio 10 and yoked variable-interval schedules in rats. Experiment 2 suggests a minimal role for the reinforced interresponse time in determining response rates on tandem variable-interval 30-s variable-ratio 10 and yoked tandem variable-ratio 10 variable-interval x-s schedules in rats.     

Three measurement problems

The aim of this essay is to distinguish and analyze several difficulties confronting attempts to reconcile the fundamental quantum mechanical dynamics with Born's rule. It is shown that many of the proposed accounts of measurement fail at least one of the problems. In particular, only collapse theories and hidden variables theories have a chance of succeeding, and, of the latter, the modal interpretations fail. Any real solution demands new physics.     

Evaluation of a preventive intervention for a self-selected subpopulation of children

Evaluated an experimental preventive intervention developed for children who perceived their parents as problem drinkers. The 8-session program was designed to improve children's coping, self-esteem, and social competence, and modify alcohol expectancies which were specified as mediators of the effects of parental alcohol abuse on child mental health. Participants were 271 self-selected 4th-, 5th-, and 6th-grade students in 13 schools. The children were randomly assigned to treatment or delayed treatment conditions and the program was given to three successive cohorts of students. A meta-analysis across three different cohorts indicated significant program effects to improve knowledge of the program content and the use of support- and emotion-focused coping behaviors for the full sample. A slightly stronger range of effects was found for a high-risk subsample. This research was funded by the National Institute of Mental Health Grant P50-MH39246 to support a Preventive Intervention Research Center and Prevention Training Grant T32-MH18387-02.     

Visual search for features and conjunctions in development.

Visual search performance was examined in three groups of children 7 to 12 years of age and in young adults. Colour and orientation feature searches and a conjunction search were conducted. Reaction time (RT) showed expected improvements in processing speed with age. Comparisons of RT's on target-present and target-absent trials were consistent with parallel search on the two feature conditions and with serial search in the conjunction condition. The RT results indicated searches for feature and conjunctions were treated similarly for children and adults. However, the youngest children missed more targets at the largest array sizes, most strikingly in conjunction search. Based on an analysis of speed/accuracy trade-offs, we suggest that low target-distractor discriminability leads to an undersampling of array elements, and is responsible for the high number of misses in the youngest children.     

On the relationship between reading, listening, and speaking: It’s different for people’s names

Two experiments are reported that tested predictions derived from the framework of face, object, and word recognition proposed by Valentine, Brennen, and Brédart (1996). The findings were as follows: (1) Production of a celebrity’s name in response to seeing the celebrity’s face primed a subsequent familiarity decision to the celebrity’s printed name. The degree of repetition priming observed was as great as that observed when a familiarity decision to the printed name was repeated in the prime and test phases of the experiment. (2) Making a familiarity decision to an auditory presentation of a celebrity’s name primed a familiarity decision to the same celebrity’s name presented visually. The magnitude of cross-modality priming was as great as the magnitude of within-modality repetition priming. This result for people’s names contrasted with the effects observed in lexical decision tasks, in which no reliable cross-modality priming was observed. The results cannot be accounted for by previous models of face and name processing. They show a marked contrast between processing people’s names and processing words. The results support the framework proposed by Valentine et al. (1996). The implications for models of speech production, perception, and reading are discussed, together with the potential of the methodology to elucidate our understanding of proper name processing.     

The Effect of Age of Acquisition on Speed and Accuracy of Naming Famous Faces

Three experiments examined whether famous faces would be affected by the age at which knowledge of the face was first acquired (AoA). Using a multiple regression design, Experiment 1 showed that rated familiarity and AoAwere significant predictors of the time required to name pictures of celebrities' faces and the accuracy of producing their names. Experiment 2 replicated an effect of AoA using a factorial design in which other attributes of the celebrities were matched. In both Experiments 1 and 2, several ratings had been collected from participants before naming latency data were collected. Experiment 3 investigated the accuracy and latency of naming celebrities without any prior exposure to the stimuli. An advantage for naming early acquired celebrities was observed even on the first presentation. The participants named the same celebrities in three subsequent presentations of the stimuli. The effect of AoA was not significant on the fourth presentation. The implications of these results for models of face naming and directions for future research are discussed.     

Computation of cone contrasts for color vision research

Cone-contrast coordinates have proved useful for representing transient test stimuli used in color vision experiments. These representations automatically take into account the spectral absorption of cones and any Weberian adaptation to steady fields of light. Under these conditions, they also can be interpreted as being an approximation to the incremental cone response. A detailed methodology is presented for making appropriate measurements and calculations of cons contrasts for any light source, especially color monitors.     

Grasp force control in older adults

Diminished tactile sensibility and impaired hand dexterity have been reported for elderly individuals. Reports that younger adults with severely impaired tactile sensibility use excessive grasp force during routine grasp and manipulation tasks raise the possibility that elderly persons likewise produce large grasp forces that may contribute to impaired dexterity. Impaired pseudomotor functioning also occurs in elderly subjects and may yield a slipperier skin surface that enhances the possibility for excessive grasp force. The present study measured grasp force in 10 elderly and 9 young adult individuals, during grasp and vertical lift of a small object, using a precision (pinch) grip of the thumb and index finger. The slipperiness of the object's gripped surfaces was unexpectedly varied. Skin slipperiness was estimated by also measuring the grasp force at which the object slipped from grasp. The older subjects employed grasp forces that were, on average, twice as large as those of the young subjects, with some producing forces many times greater than the young subjects' average grip force. Grip forces also were significantly more variable across trials in older subjects. This increased variability was not caused simply by the elderly subjects' increased grip force. A portion of the increased force was due to increased skin slipperiness. The grip force that the elderly subjects produced in excess of the slip force (the "margin of safety" against object slippage) was larger than would have been predicted from their skin slipperiness, however. It is suggested that, in part, the excessive grasp forces represent a strategic response to tactile sensibility impairment. Twopoint discrimination limina in the older subjects averaged about four times greater than in the younger subjects. Increased grasp forces in elderly persons may result from other factors, such as increased variability in grip force production. The contributions of excessive grasp forces to impaired dexterity in older persons still need to be addressed experimentally.