Transfer of configural learning between the components of a preexposed stimulus compound: implications for elemental and configural models of learning

In 2 experiments, rats received preexposure to 2 compound contexts: AB and CD for the congruent group and AC and BD for the incongruent group. Subsequently, all rats received a configural discrimination in which separate placement in contexts A or B indicated that presentations of stimulus X would be followed by food and presentations of Y would not, and separate placement in contexts C and D indicated that Y would be followed by food and X would not. In both experiments, rats in the congruent group acquired the conditional discrimination more rapidly than those in the incongruent group. These results are inconsistent with conventional associative accounts of either stimulus preexposure effects or configural learning and instead provide support for a connectionist account.     

ON THE CORRESPONDENCE BETWEEN PREFERENCE ASSESSMENT OUTCOMES AND PROGRESSIVE‐RATIO SCHEDULE ASSESSMENTS OF STIMULUS VALUE

The current study examined whether stimuli of different preference levels would be associated with different amounts of work maintained by the stimuli, as determined through progressive‐ratio schedule break points. Using a paired‐choice preference assessment, stimuli were classified as high, moderate, or low preference for 4 individuals with developmental disabilities. The stimuli were then tested three times each using a progressive‐ratio schedule (step size of 1; the break‐point criterion was 1 min). In 10 of 12 possible comparisons, higher preference stimuli produced larger break points than did lower preference stimuli.     

Examination of the influence of contingency on changes in reinforcer value

This study examined how the amount of effort required to produce a reinforcer influenced subsequent preference for, and strength of, that reinforcer in 7 individuals with intellectual disabilities. Preference assessments identified four moderately preferred stimuli for each participant, and progressive-ratio (PR) analyses indexed reinforcer strength. Stimuli were then assigned to one of four conditions for 4 weeks: fixed-ratio (FR) 1 schedule, escalating FR schedule, yoked noncontingent (NCR) delivery, and restricted access. Preference assessments and PR schedules were then repeated to examine changes in selection percentages and PR break points. Selection percentages decreased for all NCR stimuli but increased for most of the restricted stimuli. There were no systematic changes in selection percentages for either of the contingent stimuli. Break points increased, on average, for all conditions, but the increase was highest for the restricted stimuli and lowest for the NCR stimuli. These results are discussed in relation to recent basic research addressing the influence of effort on stimulus value.     

Associative change in connectionist networks: an addendum

The results of a recent study have provided direct support for the suggestion that conditional learning in rats is best characterized by a 3-layer connectionist network (M. J. Allman, J. Ward-Robinson, & R. C. Honey, 2004). In the 2 experiments reported here, rats were used to investigate the nature of the changes that occur when a stimulus compound is presented, whose components activate hidden units associated with food and no food, and either food or no food is presented. The results of both experiments, while controlling for the possible contribution of associations between these hidden units (within-layer links), provide evidence that the distribution of associative change between units in the hidden layer that are activated by the stimulus compound and those in the output layer (between-layer links) are unequal. They also indicate that associative change is more marked on trials on which no food was presented than on trials on which food was presented.     

The psychic costs of intense positive affect

Recent research indicates that happiness, or affective well-being, is related primarily to the frequency, not to the intensity, of positive affect (PA). The question arises as to why intense positive affect (PI) is not a larger contributor to subjective well-being. Whether processes that yield PI also produce intense negative affect was examined. Studies 1 and 2 suggested that cognitive mechanisms that amplify or dampen affect can carry over from positive to negative events. Study 3 demonstrated that, because of judgment mechanisms, an extremely positive event can make other events less positive. Study 4 revealed that naturally occurring intensely positive experiences are often preceded by negative ones. Study 5 suggested that the more persons valence success at a task, the happier they will be if they succeed, but unhappier if they fail. The 5 studies reveal that intense positive experiences may sometimes have costs that counterbalance their desirable nature.     

Facilitatory spatial interaction with percutaneous electrical stimuli

To measure the effect of a rectangular percutaneous conditioning shock to one finger on subjective magnitude of a suprathreshold test shock to an adjacent finger, Ss equated a contralateral matching stimulus to the test shock. The conditioning shock generally increased the apparent intensity of the test shock. This facilitation was a negatively accelerated function of test-shock current. Larger conditioning stimuli produced greater facilitation. Over limited intervals, time between conditioning and test or test and matching stimuli had no systematic effects.     

Interdisciplinary Treatment of Maladaptive Behaviors Associated with Postural Orthostatic Tachycardia Syndrome (POTS): A Case Report

The prevalence of postural orthostatic tachycardia syndrome (POTS) in adolescents and young adults has been increasing during the past decade. Despite this increase, documentation regarding treatment of these patients is just beginning to emerge. In addition, despite a call for a multidisciplinary or interdisciplinary approach, no studies have examined the efficacy of such an approach to treatment. This paper describes a case study of a 19-year-old male with debilitating POTS seen at a tertiary clinic for evaluation and subsequent intensive interdisciplinary treatment. The treatment approach is described and outcomes are presented.     

Measuring reversal learning: Introducing the Variable Iowa Gambling Task in a study of young and old normals

We developed a modification of the Iowa Gambling Task (IGT) to test whether it is primarily a measure of reversal learning. Named the Variable IGT (VIGT), the design involves a contingency reversal midway through the task. Two versions of the task enabled us to study the effect of a stronger prepotent response on the ability to identify and adapt to contingency reversal. A significant reversal delay was observed among normal young players with a more dominating reward response. Although transitory, this delay is comparable to the characteristic behavioural impairment observed in patients with damage to the ventromedial prefrontal cortex (VM), addicts, psychopaths and individuals with other self-destructive disorders: They persist in a previously rewarding behaviour despite long-term heavy costs. We also conducted the VIGT in a sample of healthy elderly adults. Results from this sample do not support VM-like or risk-aversive theories of ageing but are inconclusive regarding the frontal ageing hypothesis. Overall, our findings indicate that the VIGT is a sensitive and versatile measure of reversal learning and will serve as a useful instrument in future studies of affective decision making, addiction, and other self-destructive behaviour.