Sea lions and equivalence: expanding classes by exclusion

Experiments have shown that human and nonhuman subjects are capable of performing new arbitrary stimulus-stimulus relations without error. When subjects that are experienced with matching-to-sample procedures are presented with a novel sample, a novel comparison, and a familiar comparison, most respond by correctly selecting the novel comparison in the presence of the new sample. This exclusion paradigm was expanded with two California sea lions that had previously formed two 10-member equivalence classes in a matching-to-sample procedure. Rather than being presented with a novel sample on a given trial, the sea lions were presented with a randomly selected familiar member of one class as the sample. One of the comparisons was a randomly selected familiar member of the alternative class, and the other was a novel stimulus. When required to choose which comparison matched the sample, the subjects reliably rejected the familiar comparison, and instead selected the unfamiliar one. Next, the sea lions were presented with transfer problems that could not be solved by exclusion; they immediately grouped the new stimuli into the appropriate classes. These findings show that exclusion procedures can rapidly generate new stimulus relations that can be used to expand stimulus classes.     

Discrimination of individual vocalizations by black-capped chickadees (Poecile atricapilla)

The auditory perceptual abilities of male black-capped chickadees (Poecile atricapilla) were examined using an operant go/no-go discrimination among 16 individual vocalizations recorded at 5 m. The birds learned to discriminate about equally well among eight male chickadee fee-bee songs and eight female zebra finch (Taeniopygia guttata) distance calls. These results do not indicate that chickadees have a species-specific advantage in individual recognition for conspecific over heterospecific vocalizations. We then transferred the chickadees to a discrimination of the same songs and calls rerecorded at a moderate distance. These results showed accurate transfer of discrimination from 16 vocalizations recorded at 5 m to novel versions of the same 16 songs and calls rerecorded at 25 m. That is, chickadees recognized individual songs and calls despite degradation produced by rerecording at 25 m. Identifying individual vocalizations despite their transformation by distance cues is here described as a biologically important example of perceptual constancy.     

The length of the retention interval,forgetting, and subjective similarity

A long retention interval tends to result in the poor retention known as forgetting. A high subjective similarity between stimuli frequently produces their poor retention. Thus, a long retention interval may increase the subjective similarity between stimuli (the RIISS hypothesis), and this increase may produce forgetting. To examine this hypothesis, college students made speeded same-different discriminations between two lines or tones of different lengths or frequencies that were 400 ms or 3,300 ms apart, and they rated the similarity of these stimuli. The long interval produced poorer overall performance as expected, but also produced poorer performance on different than same stimuli, implying that it increased the subjective similarity between the initial and subsequent stimuli, and it also increased rated similarity, in support of the RIISS hypothesis. The position that stored stimuli lose less common information than distinctive information explains RIISS evidence better than does perturbation theory.     

The daily inventory of stressful events: an interview-based approach for measuring daily stressors

This study introduces the Daily Inventory of Stressful Events (DISE), an interview-based approach to the measurement of multiple aspects of daily stressors through daily telephone interviews. Using a U.S. national sample of adults aged 25 to 74 (N = 1,031), the prevalence as well as the affective and physical correlates of daily stressors are examined. Respondents had at least one daily stressor on 40 percent of the study days and multiple stressors on 11 percent of the study days. The most common class of stressors was interpersonal tension followed by work-related stressors for men and network stressors (events that occur to close others) for women. Stressors that involved danger of loss were more prevalent than stressors in which loss actually occurred. Regression analyses showed that specific types of daily stressors such as interpersonal tensions and network stressors were unique predictors of both health symptoms and mood.     

Long-term memory for concepts in a California sea lion (<Emphasis Type="Italic">Zalophus californianus</Emphasis>)

An adult California sea lion (Zalophus californianus) with extensive experience in performing discrimination learning tasks was tested to evaluate her long-term memory for two previously learned concepts. An associative concept, that of equivalence classification, was retested after a retention interval of approximately 1 year. The sea lion had originally shown emergent equivalence classification with nonsimilarity-based classes of stimuli in a simple discrimination repeated-reversal procedure as well as in a matching-to-sample procedure. The 1-year memory test revealed no decrement in classification performance in either procedure. A relational concept, that of generalized identity matching, was retested after approximately 10 years. The sea lion had originally received trial-and-error exemplar training with identity matching-to-sample problems prior to transferring the concept to novel stimulus configurations. In the 10-year memory test, the sea lion immediately and reliably applied the previously established identity concept to familiar and novel sets of matching problems. These are the first reports of long-term conceptual memory in a nonprimate species. The experimental findings are consistent with a variety of observations of sea lions in natural settings, which indicate that natal sites, feeding areas, and individuals may be remembered over long periods of time. Electronic Supplementary Material is available if you access this article at http://dx.doi.org/10.1007/s10071-002-0153-8. On that page (frame on the left side), a link takes you directly to the supplementary material. Electronic Publication     

Psychosocial Treatment Strategies in the MTA Study: Rationale, Methods, and Critical Issues in Design and Implementation

The Collaborative Multimodal Treatment Study of Children with Attention Deficit Hyperactivity Disorder (ADHD), the MTA, is the first multisite, cooperative agreement treatment study of children, and the largest psychiatric/psychological treatment trial ever conducted by the National Institute of Mental Health. It examines the effectiveness of Medication vs. Psychosocial treatment vs. their combination for treatment of ADHD and compares these experimental arms to each other and to routine community care. In a parallel group design, 579 (male and female) ADHD children, aged 7–9 years, 11 months, were randomly assigned to one of the four experimental arms, and then received 14 months of prescribed treatment (or community care) with periodic reassessments. After delineating the theoretical and empirical rationales for Psychosocial treatment of ADHD, we describe the MTA's Psychosocial Treatment strategy applied to all children in two of the four experimental arms (Psychosocial treatment alone; Combined treatment). Psychosocial treatment consisted of three major components: a Parent Training component, a two-part School Intervention component, and a child treatment component anchored in an intensive Summer Treatment Program. Components were selected based on evidence of treatment efficacy and because they address comprehensive symptom targets, settings, comorbidities, and functional domains. We delineate key conceptual and logistical issues faced by clinical researchers in design and implementation of Psychosocial research with examples of how these issues were addressed in the MTA study.Deceased     

Books in review

International Journal for Philosophy of Religion -     

The relationship between out-of-school activities and positive youth development: an investigation of the influences of communities and family

There is growing evidence that participation in constructive leisure activities facilitates positive youth development. Empirical evidence also supports the influence of families and communities on positive developmental outcomes for adolescents. This study examined the relationship among attitudes toward family and community, participation in structured out-of-school activities, and pro-social behavior. As predicted, community aspects such as opportunities available and the attitudes the youth held toward the community, as well as their attitude toward family were predictive of activity involvement. Activity involvement, in turn, was predictive of pro-social behavior. Attitude toward family was also predictive of attitude toward the community. Attitude toward community was a direct predictor of the positive developmental outcome of pro-social behavior, although contrary to the original hypothesis, family influences did not have a direct effect on pro-social behavior. Implications for continued practice and change for a variety of sectors in the positive youth development field such as educators and educational institutions, youth-serving organizations, families, and policy makers are discussed, along with recommendations for continued research in this field.