The effects of behavioral history on response acquisition with immediate and delayed reinforcement

Effects of prior exposure to the experimental chamber with levers present or absent and variable-time (VT) 60-s water deliveries arranged during one, five, or no 1-hr sessions were examined in rats during a 6-hr response-acquisition session in which presses on one lever produced water delivery immediately or after a 15-s resetting delay, and presses on the other lever canceled scheduled water deliveries. Response acquisition was (a) slower to occur when water deliveries were delayed, (b) most consistent in groups that had received five VT sessions, and (c) impaired by the presence of levers only when there had been five VT sessions and water deliveries were delayed during the acquisition session.     

Marijuana effects on human forgetting functions

It has long been known that acute marijuana administration impairs working memory (e.g., the discrimination of stimuli separated by a delay). The determination of which of the individual components of memory are altered by marijuana is an unresolved problem. Previous human studies did not use test protocols that allowed for the determination of delay-independent (initial discrimination) from delay-dependent (forgetting or retrieval) components of memory. Using methods developed in the experimental analysis of behavior and signal detection theory, we tested the acute effects of smoked marijuana on forgetting functions in 5 humans. Immediately after smoking placebo, a low dose, or a high dose of marijuana (varying in delta9-THC content), subjects completed delayed match-to-sample testing that included a range of retention intervals within each test session (0.5, 4, 12, and 24 s). Performances (discriminability) at each dose were plotted as forgetting functions, as described and developed by White and colleagues (White, 1985; White & Ruske, 2002). For all 5 subjects, both delta9-THC doses impaired delay-dependent discrimination but not delay-independent discrimination. The outcome is consistent with current nonhuman studies examining the role of the cannabinoid system on delayed matching procedures, and the data help illuminate one behavioral mechanism through which marijuana alters memory performance.     

Disability Rights,Prenatal Diagnosis and Eugenics: A Cross-Cultural View

This paper considers the disability rights critique of genetic testing in the context of different communities and the issue of nondirectiveness. Despite the wide usage of genetic diagnosis in Israel, no public debate has emerged there concerning disability rights and prenatal testing. The common attitude that emerged from interviews with Israeli representatives of organizations “of’’ and “for’’ people with genetic diseases and congenital disabilities can be described as a two-fold view of disability: support of genetic testing during pregnancy, and support of the disabled person after birth. This two-fold view is explained as a secular construction situated in legal, economic and cultural contexts. The paper concludes by considering the implications of the “two-fold view’’ of disability for the profession of genetic counseling. It is argued that awareness of the existence of conflicting views among clients—such as the view of the ‘disability critique’ as well as of the “two-fold view of disability’’—should strengthen the significance of nondirectiveness.     

Depression After Traumatic Brain Injury: A Review of Evidence for Clinical Heterogeneity

Depression represents a major source of disability among individuals who have suffered a traumatic brain injury (TBI), with estimates of prevalence in this population ranging over 50%. In comparison with other sequelae of TBI, depression is often poorly conceptualized and treated among acute care and rehabilitation professionals. One reason for this is the lack of clear etiological models for the development of depression following TBI. This paper argues that post-TBI depression actually represents a heterogeneous category, with multiple etiologic pathways and clinical implications. The literature in this area is reviewed, with an emphasis on an appreciation of the diversity within this clinical population. Conclusions focus on suggestions for differential diagnosis and treatment options.     

Response acquisition with delayed reinforcement: a comparison of two-lever procedures.

Groups of 8 experimentally naive rats were exposed during 8-hr sessions to resetting delay procedures in which responses on one lever (the reinforcement lever) produced water after a delay of 8, 16, 32, or 64 s. For rats in one condition, responses on a second (no-consequences) lever had no programmed consequences. For rats in another condition, responses on a second (cancellation) lever during a delay initiated by a response on the reinforcement lever prevented delivery of the scheduled reinforcer; responses on the cancellation lever at other times had no programmed consequences. Under both conditions and at all delays, most subjects emitted more responses on the reinforcement lever than did control rats that never received water emitted on either lever. At 8-s delays, both conditions engendered substantially more responding on the reinforcement lever than on the other lever, and performance closely resembled that of immediate-reinforcement controls. At delays of 16 and 32 s, however, there was clear differential responding on the two levers under the cancellation condition but not under the other condition. When the delay was 64 s, differential responding on the two levers did not occur consistently under either condition. These findings provide strong evidence that the behavior of rats is sensitive to consequences delayed by 8, 16, and 32 s, but only equivocal evidence of such sensitivity to consequences delayed 64 s. They also indicate that acquisition depends, in part, on the measure of performance used to index it.     

Reproductive Genetic Counseling to Asian-Pacific and Latin American Immigrants

Latin and Asian-Pacific immigrants are the fastest growing new-comer groups in the U.S. contributing to 85% of immigration totals. New immigrants experience multiple barriers to accessing genetic counseling resulting from cultural, linguistic, financial, and educational factors as well as having unique perceptions on health, illness, reproduction, and life as a whole. In addition, new immigrants lack familiarity with Western medical practices as well as genetic risk and available interventions. We provided perinatal genetic services to 2430 clients, mostly new immigrants of Latin and Asian-Pacific descent over a period of 6 years. Counseling aides sharing the clients' cultural backgrounds were employed. A study assessing the efficacy of cross-cultural education regarding advanced maternal age risk and amniocentesis was implemented and linked to a database containing demographic and clinical information. Practical observations relating to cultural beliefs in the two groups relevant to perinatal genetic counseling were made.     

Genetic counseling for a family with two distinct anomalies: A case report of a neural tube defect and 5p- syndrome in a fetus

A couple presented for genetic counseling because of an elevated maternal serum alpha fetoprotein. Ultrasound examination revealed the presence of a neural tube defect. The couple declined an amniocentesis, but chose serial ultrasound evaluations instead. Ultrasounds eventually identified microcephaly, but the couple continued to decline amniocentesis. After the child's birth, the diagnosis of 5p- syndrome was made. The couple's decision not to have an amniocentesis allowed the family their right to autonomy; however, prenatal chromosome analysis would have provided this couple with a great deal more prognostic information. We discuss the conflict between a counselor's duty to respect a client's freedom vs. duty to care for a client's welfare. We address issues of nondirective counseling and the need for more studies looking at the decision-making process in prenatal diagnosis.     

Precurrent self-prompting operants in children: "Remembering"

In Experiment I, one of three forms of collateral behavior was trained: Differential collateral behavior specific in form to one of two discriminative stimuli; Common collateral behavior of a single form regardless of the stimulus; or Nondifferential collateral behavior of either form regardless of the stimulus. Children were next given a short-delay matching-to-sample task in which the discriminative stimuli served as samples, and the children's previously trained collateral behavior terminated the delay and presented the comparison stimuli. Subjects engaging in sample-specific collateral behavior immediately acquired matching. Subjects engaging in sample-nonspecific collateral behavior failed to acquire matching or did so gradually. In Experiment II the minimal delay in the matching task was varied in a mixed sequence, first with collateral behavior required, and then with collateral behavior prohibited. When emitting collateral behavior Common and Nondifferential subjects showed delay-related decrements in matching while Differential subjects did not. When not emitting collateral behavior all subjects showed delay-related decrements in matching. Common and Nondifferential subjects matched more accurately when prohibited from emitting collateral behavior. Differential subjects matched more accurately when emitting collateral behavior. The results accord with Skinner's (1953, 1968) analysis of precurrent operants.     

Parameters affecting the maintenance of negatively reinforced key pecking

Three negative reinforcement experiments employing a key-peck response are described. In Experiment I, pigeons shocked on the average of twice per minute (imposed condition) could produce, by pecking a key, an alternate condition with correlated stimuli. Delayed shocks were added, across sessions, to the alternate condition until pecking stopped. Two of three pigeons continued to peck despite a 100% increase in shock frequency. In Experiment II, pigeons were shocked in the imposed condition four times per minute. The postresponse delay to shock was held constant by delivering, in the alternate condition, the next shock, or the next two, three, or four shocks from the imposed-condition shock schedule. All three subjects continued to peck with no change in delay to the first two postresponse shocks but with a 75% reduction in shock frequency. In Experiment III, a response produced an immediate shock followed by a shock-free period. Three of four subjects continued to respond despite reduced delay to shock. Delay-to-shock or shock-frequency reduction was sufficient to maintain key pecking, but neither was necessary. The conditions that negatively reinforce the pigeon's key peck were similar to conditions that negatively reinforce the rat's bar press.