Investigating retrospective influences on induction in rats' responding for 1% sucrose when food-pellet reinforcement is upcoming

When rats lever press for 1% sucrose reinforcement in the first half of a 50-min session, response rates are higher when food-pellet reinforcement will be available in the second half than when 1% sucrose will be available. Results of past research have suggested that, under some conditions, this induction effect is prospective in nature (i.e., controlled by the conditions of reinforcement in the present session). However, that research did not rule out the possibility that, under other conditions, retrospective factors (i.e., the conditions of reinforcement in the previous session[s]) could contribute. In the present study, rats responded in two types of session, one in which 1% sucrose reinforcement was available in both halves of the session and one in which 1% sucrose and food-pellet reinforcement were available in the first and second halves, respectively. Which type of session was in effect unsignaled and session type alternated every session (Experiment 1), every second session (Experiment 2), or after at least 20 consecutive sessions of one type (Experiment 3). Across experiments, the results indicated that it takes several sessions of one type for observable retrospective effects to occur, but those effects are short lived. These results allow the authors to identify the mechanisms that must underlie induction. The authors also discuss induction as an animal model of anticipation.     

Testing the limits of cognitive plasticity in older adults: application to attentional control

Laboratory based training studies suggest that older adults can benefit from training in tasks that tap control aspects of attention. This was further explored in the present study in which older and younger adults completed an adaptive and individualized dual-task training program. The testing-the-limits approach was used [Lindenberger, U., & Baltes, P. B. (1995). Testing-the-limits and experimental simulation: Two methods to explicate the role of learning in development. Human Development, 38, 349-360.] in order to gain insight into how attentional control can be improved in older adults. Results indicated substantial improvement in overlapping task performance in both younger and older participants suggesting the availability of cognitive plasticity in both age groups. Improvement was equivalent among age groups in response speed and performance variability but larger in response accuracy for older adults. The results suggest that time-sharing skills can be substantially improved in older adults.     

The Predictive Validity of Parent and Teacher Reports of ADHD Symptoms

The objectives were to evaluate the ability of the Inattention and Hyperactivity–Impulsivity factors of the ADHD Rating Scale-IV to differentiate children with ADHD from a control group and to discriminate children with different subtypes of ADHD. Also, we sought to determine optimal cutoff scores on the teacher and parent versions of this scale for making diagnostic decisions about ADHD. In a sample of 92 boys and girls 6 to 14 years of age referred to a regional ADHD program, we assessed ADHD diagnostic status using categorical and dimensional approaches as well as parent- and teacher-report measures. Logistic regression analyses showed that the Inattention and Hyperactivity–Impulsivity factors of the ADHD Rating Scale-IV were effective in discriminating children with ADHD from a control group and differentiating children with ADHD, Combined Type from ADHD, Inattentive Type. Although both teacher and parent ratings were significantly predictive of diagnostic status, teacher ratings made a stronger contribution to the prediction of subtype membership. Using symptom utility estimates, optimal cutoff scores on the Inattention and Hyperactivity–Impulsivity scales for predicting subtypes of ADHD were determined.     

REBT and Rationality: Philosophical Approaches

This paper argues that philosophical critiques of concepts in psychotherapy are inappropriate unless the context in which they are used is taken into account. In the case of REBT it is misleading to try to evaluate Ellis' use of rationality by matching it with the concept which has developed in modern philosophy of science. There is no pure essence of rationality which could enable it to be applied normatively in all contexts. The pitfalls of attempting this are illustrated by analysing two recent attempts to criticise rationality in REBT, by Erwin (1997) and O'Donohue and Vass (1996). We argue that Rationality in REBT can only be understood by seeing it as part of a network of categories and practices (a discursive formation) that has evolved over the last 45 years.     

Parent Ratings of Attention-Deficit/Hyperactivity Disorder Symptoms: Factor Structure and Normative Data

Changes in the diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) have necessitated the creation of new measures for clinical assessment. The factor structure of a parent rating scale containing the 18 symptoms of ADHD was examined in this study. Factor analyses and assessment of differences in ADHD ratings across sex, age, and ethnic group were conducted using a sample of 4666 participants ranging in age from 4 to 20 years old who attended kindergarten through 12th grade in 22 school districts across the United States. Two factors (Inattention and Hyperactivity–Impulsivity) were derived and normative data for a nationally representative sample are presented. A higher frequency of ADHD symptoms was found for boys, younger children, and African-American participants. Potential uses of this scale in clinical practice and research are discussed.     

On thought experiments as a priori science

Against Norton's claim that all thought experiments can be reduced to explicit arguments, I defend Brown's position that certain thought experiments yield a priori knowledge. They do this, I argue, not by allowing us to perceive “Platonic universals” (Brown), even though they may contain non‐propositional components that are epistemically indispensable, but by helping to identify certain tacit presuppositions or “natural interpretations” (Feyerabend's term) that lead to a contradiction when the phenomenon is described in terms of them, and by suggesting a new natural interpretation in terms of which the phenomenon can be redescribed free of contradiction.     

The ethics and politics of small sacrifices in stem cell research

Pluripotent human stem cell research may offer new treatments for hundreds of diseases, but opponents of this research argue that such therapy comes attached to a Faustian bargain: cures at the cost of the destruction of many frozen embryos. The National Bioethics Advisory Commission (NBAC), government officials, and many scholars of bioethics, including, in these pages, John Robertson, have not offered an adequate response to ethical objections to stem cell research. Instead of examining the ethical issues involved in sacrificing human embryos for the goal of curing fatal and disabling diseases, they seek to either dismiss the moral concerns of those with objections or to find an "accomodation" with those opposed to stem cell research. An ethical argument can be made that it is justifiable to modify or destroy certain human embryos in the pursuit of cures for dread and lethal diseases. Until this argument is made, the case for stem cell research will rest on political foundations rather than on the ethical foundations that the funding of stem cell research requires.     

Relative persistence of avoidance and positively reinforced behavior

In one experiment with rats, and a second with pigeons, subjects were trained on a schedule in which identical response dependencies applied to intermittent receipt of positive reinforcement (PR) for one group and avoidance (AV) of shock for a second group. After obtaining comparable stable training performance for groups PR and AV, persistence tests were conducted with a traditional extinction (EXT) procedure vs. response-independent (FREE) delivery of positive reinforcers or shocks. In both experiments, response elimination was rapid in EXT for groups PR and AV, and responding tended to be maintained in groups PR and AV in the FREE persistence test. These results contradict the widely held assumption that avoidance behavior is unusually resistant to extinction, and they call for a re-examination of elimination of avoidance responding.     

Spectral sensitivity of the Sooty mangabey

Purkinje shift and scotopic and photopic spectral sensitivity functions were determined for four Sooty mangabeys and five human controls using a flicker technique in a four-choice discrete trials task. Results-indicate a Purkinje shift similar in magnitude and frequency locus to that of human controls. Scotopic spectral sensitivity was almost identical to that of human controls, although both species showed reduced sensitivity relative to the standard CIE function, -at short wavelengths. Photopic spectral sensitivity disclosed enhanced sensitivity in the blue and reduced sensitivity (0.3–0.4 log units) in the red relative to human controls.