The design and evaluation of a worksharing system for experimental group living

Failure to share household chores equitably may be a major cause of the high failure rate of experimental group-living arrangements. A behavioral approach to worksharing based on a point system was implemented in one experimental group and its most important components experimentally evaluated. Experiment I showed that awarding credits produced more work than not awarding credits. Experiment II showed that making credits contingent on the outcome of a detailed inspection produced more work than awarding credits noncontingently. Experiment III demonstrated that awarding rent reductions contingent on credit earnings produced more work than awarding rent reductions noncontingently. Other evaluative data suggest that the resulting living arrangement is cheaper, more effective, and more satisfactory to the residents when compared to the most popular alternative living arrangements.     

A token economy program for chronic schizophrenic patients

Abstract.— A token economy program was applied on a ward for 12 chronic schizophrenic patients. An ABABC-design, i.e. a group reversal design with a noncontingent reinforcement phase at the end, was used to evaluate the treatment. The patients' activity-level increased from baseline to the treatment phase. During the reversal period the activity-level decreased but it increased again when the token economy was reintroduced. The non-contingent reinforcement resulted in the predicted decrease for two of the six behaviors recorded. Five of the twelve patients were discharged from the ward during the 8-month program period and none of them had been readmitted at the end of the one year follow-up. Individual treatment programs for two of the patients concerning aggressive acts, deficient eye-contact and lip-biting are described.     

A comparison of the key-peck and treadle-press operants in the pigeon: differential-reinforcement-of-low-rate schedule of reinforcement

Key pecking and treadle pressing in pigeons were compared under concurrent (key-treadle) and single-operant differential-reinforcement-of-low-rate schedules of food reinforcement ranging from 5 to 60 sec (concurrent procedure) or 5 to 120 sec (single-operant procedure). Under both procedures, the two operants followed the same general law: decreasing response rate and reinforcement rate and increasing number of responses per reinforcement as a function of increasing schedule interval. High correlations were found between key pecking and treadle pressing for the measures of response rate, reinforcement rate, and responses per reinforcement. Regression equations allowed the prediction of treadle pressing from key pecking. More bursting occurred in responding to the key, and key pecking showed a more precise temporal discrimination than treadle pressing. A test for sequential dependencies between key and treadle responses showed significant dependencies not only under the concurrent procedure but also in data created artificially by merging key and treadle sequences from different pigeons under the concurrent procedure and from the same pigeon under the single-operant procedure. It seems likely that the sequential dependencies found were due to the independent action of the schedule on each operant and that behavioral dependencies did not occur with the concurrent training procedure. The key-peck operant does not appear to have any special qualities that preclude its use in discovering general laws of behavior, at least under the differential-reinforcement-of-low-rate schedule. The usefulness of the key peck in other situations requires direct experimental study.     

The stages of acquisition in stimulus fading

Pigeons were exposed to a stimulus fading procedure in which control of responding was transferred from red and black stimuli to lines of different angular orientation. After superimposing one line on the red stimulus and the other line on the black stimulus, the intensity of the lines was gradually increased and that of the red stimulus was gradually reduced. Probes consisting of red and line stimuli presented separately were used during the course of fading to assess control exerted by each element of the compound. As the lines were faded in, they did not acquire control of responding. As red was faded out, control of responding was acquired first by the lower intensity red stimuli in combination with the line stimulus, and finally by the angular orientation of the lines. Probes also determined the point at which the line stimuli, presented alone, would maintain a high degree of stimulus control. The results demonstrated that new stimuli in fading acquire dimensional control of responding in two sequential stages. Acquisition of stimulus control in fading was explained in terms of attenuation of stimulus blocking.     

Serial position functions for letter identification at brief and extended exposure durations

The properties of serial position functions for tachistoscopic report were investigated over a wide range of viewing times. Four-letter strings of random consonants were presented in varying display locations relative to the fixation point with the observers’ eye movements monitored to limit them to a single fixation for each display. Salient properties of the serial position curves include an overall central-peripheral gradient, higher performance at the ends than the interior of letter strings regardless of absolute location, and left-right asymmetry in the visual field, all of these being largely independent of viewing time. Errors reflecting loss of positional information are prominent even at extended viewing times, are more nearly symmetrical in the left and right visual fields than other types of errors, and, in contrast to item errors, occur less frequently in letter sequences that have high frequencies in English. Further, transposition errors exhibit a pronounced peripheral-to-central drift, possibly reflecting gradients of positional uncertainty. Such gradients may be implicated in the peripheral-central asymmetry of the lateral interference effects exerted by other letters on a target letter in a nonfoveal location.     

Proprioceptive space perception after anaesthetization of the mid-interphalangeal joint of the finger

The effect of a digital block on the voluntary positioning of the index finger from a point of extreme extension through 45° flexion was examined in 12 subjects. A xylocaine ring block of the second proximal interphalangeal joint was used to eliminate the joint receptors while weights were attached to the finger. An inverse relationship was found between weight and distance moved when the subject was required to move the index finger of the nonpreferred hand to the required position. The results indicate that the muscular system is ancillary to the joint system in proprioceptive space perception.     

Lump detection in simulated human breasts

Sixteen observers palpated silicone models of human breasts containing lumps 1.6-12.1 mm in diameter. Detectability depended on the size of the lump, producing a systematic psychometric function. In eight observers who participated in three or more sessions, performance improved with practice, with most improvement occurring within one or two 26-trial sessions. Three-week retention measures disclosed no appreciable decrease in performance, but a significant correlation was found between the number of lumps detected and duration of trial (p < .01). There was no difference in performance between four observers who used their preferred hands and four observers who used their nonpreferred hands. These data establish that examination of breast models for the detection of lumps simulating cancer is a task amenable to experimental analysis.