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Biomedical subjects

A Kaufman

Publications and source records attributed to A Kaufman.

At least 163 records · Page 9Linked to original sources
PubMed1969

Intermittent punishment of human responding maintained by intermittent reinforcement.

To determine the effects of variable-interval shock punishment on behavior maintained by variable-interval and variable-ratio reinforcement, human subjects' key-pressing behavior was reinforced with money on a four-component multiple schedule. Components 1 and 2 were variable-interval 30-sec, and Components 3 and 4 were variable-ratio 210. After responding was stabilized, response-contingent electric shock was scheduled on a variable-interval 10-sec schedule during the second and fourth components of each cycle. Subjects instructed as to the reinforcement contingencies showed gradually increasing suppression of variable-interval responding at increasing shock intensities and either very high or very low rates of variable-ratio responding at higher intensities. Minimally instructed subjects showed suppression at higher shock intensities, but no clear differential suppression as a function of reinforcement schedule. Recovery from initial suppression was observed within sessions.

Journal Article↗
PubMed1969

Effects of instructions and reinforcement-feedback on human operant behavior maintained by fixed-interval reinforcement.

In three experiments, human subjects were trained on a five-component multiple schedule with different fixed intervals of monetary reinforcement scheduled in the different components. Subjects uninstructed about the fixed-interval schedules manifested high and generally equivalent rates regardless of the particular component. By comparison, subjects given instructions about the schedules showed orderly progressions of rates and temporal patterning as a function of the interreinforcement intervals, particularly when feedback about reinforcement was delivered but also when reinforcement-feedback was withheld. Administration of the instructions-reinforcement combination to subjects who had already developed poorly differentiated behavior, however, did not make their behavior substantially better differentiated. When cost was imposed for responding, both instructed and uninstructed subjects showed low and differentiated rates regardless of their prior histories. It was concluded that instructions can have major influences on the establishment and maintenance of human operant behavior.

Journal Article↗
PubMed1968

Facilitation and suppression of human loss-avoidance by signaled, unavoidable loss.

A 15-sec stimulus followed by unavoidable monetary loss was presented to human subjects who were avoiding loss on a free-operant schedule. As has been observed in studies where shock is the aversive event, initial reactions to the pre-loss stimulus were transient increases in overall and stimulus rates. Unlike shock studies, continued training produced decreased rates, in the presence of the 15-sec stimulus, which were maintained in two of three subjects. Subsequent observations indicated that lowered rates were a function of the subject's rate of avoidance responding, the duration of the stimulus, and the scheduling of avoidable losses. Increasing the duration of the stimulus eliminated lowered rates in the presence of the stimulus and subsequent exposures to conditions which previously produced lowered rates did not result in recovery of the phenomenon. Introduction of the pre-loss stimulus on an extinction baseline (avoidable losses were omitted), however, reinstituted lowered rates. It is proposed that the pre-loss stimulus assumed discriminative control over low rates because responding in the presence of the stimulus was ineffective in avoiding the unavoidable loss. Recovery from lowered rates is attributed to the occurrence of avoidable losses during the stimulus period, and maintenance of lowered rates on the extinction schedule to the omission of such avoidable losses.

Avoidance Learning↗
PubMed1968

Suppression of behavior by timeout punishment when suppression results in loss of positive reinforcement.

This investigation, using rats as subjects and punishment by timeout for responses maintained on a ratio schedule, sought to determine whether behavior would be suppressed by timeout punishment when such suppression also reduced reinforcement density or frequency. A series of experiments indicated that timeout punishment suppressed responding, with the degree of suppression increasing as a function of the duration of the timeout period. Suppressive effects were found to decrease as a function of increases in deprivation (body weight) and were eliminated when the punished response also was reinforced. It was concluded that timeout can produce aversive effects even when loss of reinforcement results. An alternative interpretation of the findings, based on the effects of extinction periods and delay of reinforcement on chained behavior, was discussed.

Animals↗
PubMed1966

Human, free-operant avoidance of "time out" from monetary reinforcement.

To assess the aversive effects of withdrawing monetary reinforcement, human subjects were exposed to a free-operant avoidance procedure in which periods of no reinforcement occurred if the subject failed to respond, and each response postponed withdrawal of reinforcement. Avoidance behavior was developed either through specific instructions about the consequence of responding or through preliminary escape-avoidance training. In all cases, rates of response were found to be a positively accelerated function of decreases in the duration by which responding postponed reinforcement withdrawal. The findings with respect to the function relating avoidance behavior to the interval of postponement were viewed as similar to those obtained when shock is used as the aversive event in free-operant avoidance conditioning.

Avoidance Learning↗
PubMed1965

Punishment shock intensity and basal skin resistance.

The relationship between punishment shock intensity and basal skin resistance (BSR) was investigated in two sessions with human females selected for their ability to maintain a fairly substantial operant rate under a wide range of shock intensities. In both sessions each button-pressing response was reinforced with a counter tally. Subjects were paid one cent for each 20 counts. In session 1, punishment followed each response during alternate 4-min periods; in session 2 punishment was programmed in all 4-min periods. Shock intensities were presented randomly among the 4-min shock periods, with the restriction that the first three presentations occurred in ascending order. Operant responding showed some suppression at higher shock intensities in session 1, with substantial recovery in most subjects during session 2. Respondent behavior was characterized by greater activity at successively higher intensities, with recovery at all shock levels, especially the lowest levels, apparent during the second session.

Conditioning, Operant↗
PubMedDate not supplied

Ambulatory medical education: a reconsideration of sites and teachers.

This paper deals with the varied sites and teachers that can and should be used in educating residents and medical students in ambulatory care. A basic premise is that sites other than academic medical centers and teachers other than physician faculty members should be among those used. The paper describes how institutions have used non-traditional sites and teachers. Then, after emphasizing the need to choose settings according to curricular objectives, it discusses teaching sites, both hospital-based (general medical, specialty, and multidisciplinary clinics) and community-based (home care settings, rural clinics, nursing homes, and community clinics). Next it describes the array of current and potential teachers, which includes generalist and specialist physician faculty members, community physicians, residents, and allied personnel such as pharmacists and nurses. The paper also discusses forces resisting and supporting the use of new sites and teachers. It ends with general recommendations.

Ambulatory Care↗
PubMedDate not supplied

Measurement of access flow during hemodialysis using the constant infusion approach.

With reversed placement of blood lines and with a peripheral arteriovenous access, hemodialysis recirculation (R) consists of a local access component, and a central cardiopulmonary component that must be separated for the calculation of access flow (Qac) using indicator dilution principles. With indicator injections that follow constant infusion principles Qac = (1 - Rx)/(Rx(1 - CPR)) x (Qb,x - UFR), where Qb is the extracorporeal blood flow, where UFR is the ultrafiltration rate, and where the index x indicates reversed placement of blood lines. CPR, the amount of cardiopulmonary recirculation (CPR = Qac/CO) is determined from two recirculation measurements with correct (index n) and with reversed (index x) placement of blood lines CPR = Rn(1 - Rx)/Rx(1 - Rn) x (Qb,x - UFR)/Qb,n. Qac was measured in 11 hemodialysis (HD) patients using a thermodilution device tested in an in vitro set-up based on constant infusion principles. Mean Qac was 1.135 L/min and 1.054 L/min for measurements done early and late in dialysis. The coefficient of variation was +/-7.3% and +/-8.6%, respectively. Repeated measurements of access flow in HD patients showed good reproducibility (Qac.1 = 1.01*Qac.0, r2 = 0.98), with the regression line not different from the line of identity; however, in vivo results remain to be validated by an independent technique.

Arteriovenous Shunt, Surgical↗