Biomedical subjects

D M Dougherty

Publications and source records attributed to D M Dougherty.

36 records · Page 2Linked to original sources

PubMed1998

Immediate versus delayed visual memory task performance among schizophrenic patients and normal control subjects.

In an exploratory study, 10 schizophrenic patients and 10 normal control subjects performed immediate and delayed memory tasks, which were variants of previously developed continuous performance tests. Both tasks required participants to identify five-digit numbers which were repeated. Numbers were presented in series for 500 ms each and separated by a 500-ms time-out period. In the immediate memory task, subjects were to respond if a number was identical to the one that had immediately preceded it. The delayed memory task differed from the first task in that a longer delay (3.5 s) between stimuli was introduced, and during this delay distracter stimuli appeared. While normal control subjects performed accurately on both tasks (exceeding 80% correct detections), schizophrenic patients performed poorly, performing worse on the delayed memory task than on the immediate memory task. Rates of commission errors (responses made to similar, but not identical numbers) were nearly equal between groups on the immediate memory task, but on the delayed memory task normal control subjects made relatively more commission errors while schizophrenic patients made fewer commission errors. No differences in response latencies were observed between subject groups or tasks. This paradigm may prove useful in discriminating subtle differences in immediate and delayed memory capability among psychiatric populations and normal control subjects.

Adult↗

PubMed1998

Self-reported impulsivity is correlated with laboratory-measured escape behavior.

Aggression has been previously correlated with impulsive personality. In the present study, Barratt Impulsiveness Scale (BIS) scores of 40 male controls aged 15-40 years were related to the frequency of free-operant aggressive and escape responses toward a fictitious antagonist. Participants earned "points" worth money with repeated button presses on a fixed-ratio schedule and were provoked by the periodic subtraction of a point. These subtractions were blamed on the behavior of a (fictitious) other participant, and aggressive responses (presses of a separate button) were defined as those emitted by the participant with an intent to subtract earnings from the other (fictitious) participant. BIS scores were not correlated with frequency of point-subtracting (aggressive) responses to the point subtractions, but they were correlated with the frequency of escape responses on a third button, which the participant was told would protect his points from subtraction for an unspecified period of time. These results suggest that among normal controls, impulsivity might be characterized by some sensitivity to aversive stimuli.

Adolescent↗

PubMed1998

Antisocial personality disorder and alcohol-induced aggression.

This study compared the effects of alcohol on aggressive responding between subjects with antisocial personality disorder (ASPD) and subjects without ASPD. Eighteen alcohol drinking subjects (10 subjects without ASPD and 8 subjects with ASPD) underwent testing on a laboratory measure of aggression, the Point Subtraction Aggression Paradigm, after consumption of placebo and three doses of alcohol (0.25 g/kg, 0.5 g/kg, and 1.0 g/kg). There was a significant difference in the effect of alcohol on aggressive responding on the Point Subtraction Aggression Paradigm between subjects with ASPD and subjects without ASPD. Subjects with ASPD had a greater increase in aggressive responding after alcohol, compared with non-ASPD subjects. There was no difference between the two groups in the effect of alcohol on monetary-reinforced responding.

Adult↗

PubMed1998

Differences in alcohol expectancy between aggressive and nonaggressive social drinkers.

Previous reports have shown that drinkers with aggressive personalities not only hold the strongest beliefs that alcohol facilitates aggressive behavior, but they also display the greatest increases in laboratory aggression after receiving alcohol. Given that several studies have demonstrated that a portion of the behavioral and subjective effects of alcohol are due to psychological expectancy, this study explored whether aggressive drinkers have elevated intoxication expectancies from laboratory beverages with unknown alcohol content. The rates of aggressive responses emitted in a money subtraction aggression model under baseline conditions were used to select an aggressive group and a nonaggressive group, each with five male and five female participants. Subjects then ingested and rated each of three placebo (1 ml alcohol) beverages administered hourly during a subsequent laboratory visit, and rated a series of three 0.35 g/kg of alcohol beverages the following day. Whereas nonaggressive subjects clearly discriminated the relative alcohol content of alcohol and placebo drinks, aggressive subjects gave progressively elevated shot equivalent ratings to placebo drinks, similar to their ratings of alcohol doses. However, despite similar self-reported drinking histories, aggressive subjects reported anticipating only half the intoxication from the alcohol doses (and in fact achieved a lower peak breath alcohol concentration) than was expected by nonaggressive subjects.

Adult↗

PubMed1997

Antisocial personality disorder and aggression in recently abstinent cocaine dependent subjects.

To study the relationship between cocaine abstinence symptoms, personality, and aggression, we used the Point Subtraction Aggression Paradigm (PSAP) to measure aggression in 18 subjects admitted for the treatment of cocaine dependence. Eight subjects met criteria for antisocial personality disorder (ASPD). There was a significant correlation between presence of ASPD and frequency of aggressive responding by stepwise multiple regression. When presence of ASPD was factored out of the correlations, there was no significant relationship between aggressive responding and cocaine craving, withdrawal symptoms, amount of cocaine used, or length of time since use. These preliminary results suggest that in cocaine dependent individuals seeking treatment, current aggression is most dependent on the individual's previous aggressive behavior.

Adult↗

PubMed1997

A positive correlation between self-ratings of depression and laboratory-measured aggression.

Aggression and depressive symptoms have been linked using self-rating scales as measures of aggression. In order to study this relationship using an objective measure of aggression, we studied normal controls (42 women and 23 men) with the Point Subtraction Aggression Paradigm (PSAP) and the Beck Depression Inventory (BDI). There was a significant positive correlation (r = 0.442, P = 0.003) between the level of aggressive responding on the PSAP and the level of depressive symptoms on the BDI in women but not in men (r = 0.064, P = 0.773). This study provides some evidence of a link between aggressive behavior and depressive symptoms in a non-clinical population, possibly due to a common neurochemical etiology.

Adolescent↗

PubMed1997

Studies of violent and nonviolent male parolees: I. Laboratory and psychometric measurements of aggression.

Male parolees were recruited into a laboratory study to determine the relationship between their previous aggression history, psychometric measures of aggression, and behavioral measures of aggressive responding using a laboratory methodology: the Point Subtraction Aggression Paradigm. Subjects were assigned to a violent or nonviolent group based upon their criminal history. Subjects participated in sessions in which they were given three response options defined as: (1) nonaggressive responding which earned money, (2) aggressive responding which ostensibly subtracted money from another fictitious person, (This responding was defined as aggressive since it resulted in the ostensible delivery of an aversive stimulus (subtraction of money) to another person), and (3) escape which protected the subject's earnings from subtractions initiated by the other person. Results indicated that the violent subjects emitted significantly more aggressive responses than subjects in the nonviolent group. The number of aggressive responses parolees emitted was significantly correlated with most psychometric measures of aggression. This study provides external validity for our laboratory measurement of human aggressive responding, since aggressive responding was directly related to violent criminal histories.

Adult↗

PubMed1997

Studies of violent and nonviolent male parolees: II. Laboratory and psychometric measurements of impulsivity.

Males parolees were recruited into a laboratory study to determine the relationship between their previous criminal history (violent versus nonviolent), and behavioral and psychometric measures of impulsivity. During sessions, subjects were given two response options defined as: 1) an impulsive choice--small monetary reward after a short fixed delay; and 2) a self-control choice--a larger monetary reward after a variable longer delay. Based upon an extensive experimental literature in animals and humans related to delay of gratification, the degree of impulsivity was defined as the proportion of trials on which the subject selected the impulsive option. Our results indicated that the violent subjects selected the impulsive option significantly more often than the nonviolent parolees. The number of impulsive responses parolees emitted was significantly correlated with the number of aggressive responses reported in an earlier paper. This study provides support for the relationship between impulsivity and aggression among male parolees.

Adult↗

PubMed1997

The influence of menstrual-cycle phase on the relationship between testosterone and aggression.

Plasma testosterone levels and aggressive behavior were measured in 12 women with and without perimenstrual affective symptomatology (e.g., depression, irritability) during the menstrual, midfollicular, ovulatory, and premenstrual phases of the menstrual cycle. The Point Subtraction Aggression Paradigm was used to quantify aggressive response to provocation. Subjects had two response options: a point-maintained option (100 presses earned a point worth 10 cents) and an aggressive response option (10 presses ostensibly subtracted a point from a fictitious partner's counter). Subjects were provoked by the periodic subtraction of a point that was attributed to the responding of a fictitious opponent. Although plasma testosterone levels (determined by radioimmunoassay) increased significantly during the ovulatory phase, aggressive response to provocation remained unchanged across the menstrual cycle. Plasma testosterone did not differ between the 2 groups during any phase. A relationship between plasma testosterone levels and use of the aggressive response option was seen only during the midfollicular phase (Spearman r = .673, p = .017). These preliminary data suggest that: 1. The relationship in female subjects between endogenous testosterone and aggressive behavior is inconsistent; 2. self-report of perimenstrual symptomatology is a more consistent predictor of aggressive behavior across the menstrual cycle than plasma testosterone; and 3. perimenstrual emotional symptomatology is not related to testosterone levels.

Adolescent↗

PubMed1996

Tryptophan depletion and aggressive responding in healthy males.

In order to study the effect of decreasing plasma tryptophan levels on aggressive responding in a controlled laboratory setting, we administered two doses (25 g and 100 g) of a tryptophan-free amino acid mixture to ten healthy male subjects after 24 h of a low tryptophan diet. Subjects were screened for current or past psychiatric, or non-psychiatric medical illness. Aggressive responding on a free-operant laboratory measure of aggression (the Point Subtraction Aggression Paradigm) and plasma tryptophan levels were measured before and after drinking the amino acid mixture. There was a significant increase in aggressive responding 5 h after the 100 g mixture and a significant increase in aggressive responding 6 h after the 25 g mixture compared to a baseline day when no drink was administered. There was also a significant decrease in plasma tryptophan at 5 hours after ingestion compared to baseline for both doses of amino acid mixture. This study supports the hypothesis that tryptophan depletion increases aggressive responding in healthy males in a laboratory setting, probably by decreasing brain serotonin.

Adult↗

PubMed1996

The effects of alcohol on the aggressive responding of women.

OBJECTIVE: The purpose of this study was to determine the effects of a range of alcohol doses on the aggressive responding of women. METHOD: The Point Subtraction Aggression Paradigm was used. It has two response options available to the subject: (1) point-maintained responding, emitting 100 responses on one button earned the subject 10 cents; and (2) aggressive responding, emitting 10 responses on an alternative button ostensibly subtracted 10 cents from another person also working to earn money. Aggressive responses were engendered by a random-time schedule of point loss (every 6 sec. to 120 sec.), and instructions attributed these point losses to button presses made by another fictitious subject. Ten female subjects participated, and each experienced placebos and three alcohol doses, 0.25, 0.50, and 1.00 g of 95% alcohol per kg of body weight. RESULTS: The most important finding was that the 1.00 g/kg alcohol dose produced statistically significant increases in aggressive responding relative to placebo. There was, however, a small subset of individuals whose greatest increase in aggressive responding occurred after consuming the 0.25 g/kg alcohol dose. Rates of point-maintained responding were unaffected by the 0.25 and 0.50 g/kg alcohol doses and slightly suppressed by the 1.00 g/kg alcohol dose. CONCLUSIONS: These results are important because the handful of previous studies with women have provided little evidence for increased aggression after alcohol consumption in women. These observed inconsistencies between this study and previous studies may be attributed to procedural differences, which have varied considerably across studies.

Adult↗

PubMed1994

Effects of social context, reinforcer probability, and reinforcer magnitude on humans' choices to compete or not to compete.

In the first two experiments, subjects' choices to earn points (exchangeable for money) either by competing with a fictitious opponent or by not competing were studied. Buskist, Barry, Morgan, and Rossi's (1984) competitive fixed-interval schedule was modified to include a second response option, a noncompetitive fixed-interval schedule. After choosing to enter either option, the opportunity for reinforcers became available after the fixed-interval's duration had elapsed. Under the no-competition condition, points were always available after the interval had elapsed. Under the competition condition, points were available based on a predetermined probability of delivery. Experiments 1 and 2 examined how reinforcer probabilities and reinforcer magnitudes affected subjects' choices to compete. Several general conclusions can be made about the results: (a) Strong preferences to compete were observed at high and moderate reinforcer probabilities; (b) competing was observed even at very low reinforcer probabilities; (c) response rates were always higher in the competition component than in the no-competition component; and (d) response rates and choices to compete were insensitive to reinforcer-magnitude manipulations. In Experiment 3, the social context of this choice schedule was removed to determine whether the high levels of competing observed in the first two experiments were due to a response preference engendered by the social context provided by the experimenters through instructions. In contrast to the first two experiments, these subjects preferred the 60-s fixed-interval schedule (formerly the no-competition option), indicating that the instructions themselves were responsible for the preference to compete. This choice paradigm may be useful to future researchers interested in the effects of other independent variables (e.g., drugs, social context, instructions) on competitive behavior.

Adult↗

PubMed1994

The effects of smoked marijuana on progressive-interval schedule performance in humans.

In three experiments, 8 human subjects participated in a study of the effects of smoked marijuana on progressive-interval schedule performance. A two-component chained progressive-interval fixed-interval schedule of point delivery was used. In the progressive-interval component, the interval length began at 20 s and increased either geometrically or arithmetically (by either 20 s, 40 s, 80 s, 100 s, or 160 s) on each subsequent interval. After this interval elapsed, a single button press produced the fixed-interval component, with a total of five reinforcers of varying magnitude ($0.05, $0.20, or $0.40) available on a fixed-interval 20-s schedule. After the five reinforcer deliveries, the schedule returned to the initial progressive-interval component. Several relationships were found among rates of responding, postreinforcement pauses and drug administration in the progressive-interval component: (a) Postreinforcement pauses increased as the temporal requirements of the progressive-interval schedule increased; (b) rates of responding during successive progressive-interval components rapidly decreased to low rates of responding after the first few progressions; (c) postreinforcement pauses decreased systematically as dose of smoked marijuana increased; and (d) rates of responding increased after smoking active marijuana but not after smoking placebo cigarettes. Results are discussed in the context of behavioral control and relevance to other studies that have investigated the effects of smoked marijuana on schedule performance.

Adult↗

PubMed1993

Adolescent Health. Reflections on a report to the U.S. Congress.

The Office of Technology Assessment (OTA) found that the conventional wisdom that American adolescents are so healthy that they do not require health and related services is not justified; U.S. adolescents often face formidable barriers to obtaining needed health care, and relatively little appropriate attention has been paid to adolescents by the federal government. OTA suggested that Congress could act to (a) increase adolescents' access to health care by supporting comprehensive health services specifically for adolescents, (b) restructure the federal role in adolescent health by creating an office of adolescent health in the U.S. Executive Branch, and (c) improve adolescents' social environments by providing more support to families of adolescents, limiting adolescents' access to firearms, supporting the expansion of their recreational opportunities, and further increasing opportunities for community service. Federal actions taken since OTA's report are summarized.

Adolescent↗

PubMed1993

Generalization of a tactile stimulus in horses.

Using horses, we investigated the control of operant behavior by a tactile stimulus (the training stimulus) and the generalization of behavior to six other similar test stimuli. In a stall, the experimenters mounted a response panel in the doorway. Located on this panel were a response lever and a grain dispenser. The experimenters secured a tactile-stimulus belt to the horse's back. The stimulus belt was constructed by mounting seven solenoids along a piece of burlap in a manner that allowed each to provide the delivery of a tactile stimulus, a repetitive light tapping, at different locations (spaced 10.0 cm apart) along the horse's back. Two preliminary steps were necessary before generalization testing: training a measurable response (lip pressing) and training on several reinforcement schedules in the presence of a training stimulus (tapping by one of the solenoids). We then gave each horse two generalization test sessions. Results indicated that the horses' behavior was effectively controlled by the training stimulus. Horses made the greatest number of responses to the training stimulus, and the tendency to respond to the other test stimuli diminished as the stimuli became farther away from the training stimulus. These findings are discussed in the context of behavioral principles and their relevance to the training of horses.

Animals↗

PubMed1991

Elicited responding in chain schedules.

An omission procedure was employed to study elicited pecking in the first component of a two-component chain schedule. Both components were fixed-interval schedules correlated with colored keylights. The first response following the initial-link schedule produced a second fixed-interval schedule. We studied several fixed-interval lengths in two conditions: a standard response-dependent condition and an omission-contingent condition. The omission-contingent condition differed from the response-dependent condition in that responses during the initial fixed interval terminated the trial (omitting the terminal component and grain). If the terminal component was not omitted, a response following the terminal link's requirement produced 4-s access to grain. Pigeons responded during more than 70% of the initial links in the omission-contingent condition and responded during more than 90% of the initial links in the response-dependent condition. In general, rates of responding were consistent with the percentage data. The responding in the omission condition suggests that there may be elicited pecking, in chain schedules using pigeons, that is not the result of contingent conditioned reinforcement.

Animals↗

PubMed1991

Stimulus generalization, discrimination learning, and peak shift in horses.

Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms.

Animals↗

PubMed1990

Assessing information for consumers on the quality of medical care.

In recent years support for better public information on the quality of medical care has intensified, while the validity of the information available has been questioned. To address these concerns, we evaluated the reliability and validity of using each of 10 possible indicators to measure hospital and physician quality and the feasibility of providing the results to the public. We found that several of these indicators can provide useful, though not definitive, information on quality. In general, we advise consumers to combine information from more than one year and from more than one indicator to increase the likelihood that the relationship is accurate. For the provision of information on quality to achieve its potential, certain deficiencies in quality assessment must be addressed by both public and private policies. Strengthening the validity of quality assessments is vital to improve their credibility and to minimize negative effects on medical providers, individual consumers, and health care programs.

Clinical Competence↗