An experimental analysis of impulsivity and impulse control in humans

In choosing between small, immediate and large, delayed reward, an organism behaves impulsively if it chooses the small reward and shows impulse control if it chooses the large reward. Work with nonhumans suggests that impulsivity and impulse control may be derived from gradients of delayed reinforcement. A model developed by Ainslie and by Rachlin suggests that preference for the rewards should be a function of when the choice is made: small reward with no delay may be preferred to large reward with delay X, but adding delay T to both alternatives should shift preference to the large reward. Three experiments investigated this preference reversal in humans, using termination of 90 dba white noise as the reinforcing event. Experiment 1 showed that under some instructional conditions 90-sec noise off with no delay was preferred over 120-sec noise off after a 60-sec delay, but that preference shifted to the large reward when a 15-sec delay (T) was added to both alternatives. Experiment 2 replicated this preference reversal under two conditions of large, delayed reward, and with three rather than two values of T. Experiment 3 confirmed this effect of T and showed that some humans committed themselves to the large reward when commitment could be made some time before presentation of the reward alternatives. These data support the Ainslie-Rachlin model and extend it to human choice behavior.     

SOCIAL IDENTITY IN PUERTO RICO*

This study examines the social identity of 384 high school students from four age levels (10, 12, 15 and 17 years-old) in Puerto Rico. This complex society represents an interesting context because of the potential relevance of a number of dimensions for identity including language, cultural heritage, economic status, religion and political beliefs. An important methodological refinement is introduced in order to permit simultaneous examination of these various dimensions in terms of Puerto Rican identity. Three major dimensions of the students' social identity emerged from multidimensional scaling analyses and these were seen to contrast with previous research on ethnic identity in Canada, the United States and Wales.     

The science, fiction, and reality of embryo cloning.

Although many scientists view cloning as a useful procedure for scientific research into early embryo development -- one that cannot currently be used to produce multiple copies of humans -- the popular literature has led some individuals to view it as sinister. To address the concerns of the public, various conceptions of cloning are distinguished and their basis in fact analyzed. The possible uses, benefits, and detriments of both embryo splitting and nuclear transplantation are explained. Once the nature and purposes of cloning are understood, and the distinctive ethical dilemmas created by embryo splitting and nuclear transplantation are sorted out, these procedures should be clinically implemented to assist in vitro fertilization treatment for those who are infertile and to further other therapeutic and investigational efforts in medicine.     

Suicide without explicit precursors: a state of secret despair?

Although it is usually assumed that all those who commit suicide give some prior indication of their intention to take their own life, there is growing evidence that a small but significant proportion of suicides occur without any clear, explicit indicators. It is proposed that these suicides share similar pathways to other suicides but that the despair involved is not expressed so clearly, often being kept secret. In order to identify such suicides and potential suicides it is helpful to have an indicator of the dominant sub‐sets of constituents that are precursors to suicide. A 14‐item Suicide Precursors Scale (SPS) was therefore developed. This was applied to 128 cases of suicide that occurred between January 1997 and December 2000 in Stockport (South Manchester, UK). A very high alpha coefficient of 0.98 supported the reliability and homogeneity of the SPS. A Multi‐Dimensional Scaling (MDS) analysis of the SPS revealed three prototypical sub‐sets of expressions of suicidal actions—illness, life circumstances, and depressive history. These are offered as coherent themes in the life of potential suicides, which may be of assistance both in determining whether an equivocal death is suicide or not, and in alerting caring agencies to the potential for suicide even when the despair is kept secret. Copyright © 2004 John Wiley & Sons, Ltd.     

Student mental health: how can psychiatrists better support the work of university medical centres and university counselling services?

Student psychiatric morbidity is rising. Whilst the influence of university counselling services is widely reported, NHS involvement by psychiatrists and general practitioners is not so well described. Counselling and mental health service providers for students at the University of Leeds were approached for numerical data and a university Group on Student Mental Health discussed the findings. The Student Counselling Centre, the University Medical Practice and a dedicated student psychiatric clinic have all seen a rise in referral rates. The University Medical Practice has also seen a rise in the prescribing of psychoactive medication. Collaborative links at the University of Leeds are explored and options for the future discussed. These include self-help over the internet, a research project to assess student mental health needs and the provision of a dedicated NHS psychiatric team for the university.     

Behavioral and genetic characterization of habituation using Caenorhabditis elegans

This review surveys the literature that investigates the behavioral characterization and cellular and molecular mechanisms of habituation using the model organism Caenorhabditis elegans. In 1990, C. elegans was first observed to show habituation to a non-localized mechanical tap. The parameters that govern this behavioral plasticity in C. elegans were subsequently characterized, which lead to the important hypothesis that habituation is mediated by multiple mechanisms. Many tools are available to C. elegans researchers that allow for relatively easy genetic manipulation. This has lead to a number of recent genetic studies that have begun to identify key genes and molecules that play a role in the mechanisms of habituation. Some of these genes include a vesicular glutamate transporter, a glutamate receptor subunit, a dopamine receptor and downstream intracellular signaling molecules, such as G proteins and kinases. Some of these genes only affect certain parameters of habituation, but not others supporting the hypothesis that multiple mechanisms mediate habituation. The field of research has also led to the dissection of different phases of memory (short-term vs. long-term memory for habituation), which are triggered by different training paradigms. The differences in mechanism between these various forms of memory are also beginning to be revealed.     

Reliability of the Child and Adolescent Needs and Strengths-Mental Health (CANS-MH) Scale

We examined the interrater reliability of the Child and Adolescent Needs and Strengths-Mental Health (CANS-MH) scale among researchers and between researchers and clinicians. All children presenting to a treatment facility for either protective or mental health needs were eligible to be included in the study. As part of standard assessment procedure, all children entering the facility were described by caseworkers using the CANS-MH. A random sample of 60 cases was selected and researchers made retrospective assessments using the CANS-MH based on chart review. Results of the interrater reliability support previous findings that the CANS-MH is a reliable measure of clinical and psychosocial needs and strengths. Results also suggest that ratings on the CANS-MH based on medical record abstraction by researchers relate to ratings performed by clinical staff, demonstrating the clinical and research utility of the CANS-MH. The CANS-MH can be used reliably to assess the type and severity of problem presentation, risk behaviors, functioning, care intensity and organization, caregiver capacity and strengths among children with protective and mental health needs. In addition, items of the CANS-MH appear to be reliable supporting the use of these items individually. Findings are relevant to the ongoing delivery of clinical services, monitoring of quality assurance, and outcomes.