A new approach to the formation of equivalence classes in pigeons

Four pigeons were given simultaneous discrimination training with visual patterns arbitrarily divided into two sets, with the stimuli in one set designated A1, B1, C1, and D1 and those in the other set designated A2, B2, C2, and D2. In sequentially introduced training phases, the pigeons were exposed to a series of reversals to establish AB and then CD equivalences. In subsequent testing sessions, a subset of stimuli from one set served as positive stimuli and those from the other set as negative stimuli on training trials, and transfer of the reinforced relation to other members of the sets was tested with nonreinforced probe trials. The pigeons were trained further on AC and BD equivalences and then were tested for the emergence of untrained AD and BC equivalences. Two of the 4 pigeons exhibited the emergence of one of these untrained equivalences, evidence for the emergence of transitive relations. This finding suggests that the pigeons established three-member functional equivalence classes by incorporating separately trained multiple equivalence relations. Repeated reversal training and probe testing enabled us to explore the formation and expansion of functional equivalence classes in pigeons.     

A multisource exploration of the friendship patterns of children with and without learning disabilities

Friendship patterns of 117 children with learning disabilities (LD) and 115 children without LD in Grades 4–8 were examined. In comparison with children without LD, boys with LD had fewer mutual friends, children with LD had more friends with learning problems and more younger friends, and children with LD in Grades 4–6 had less stable relationships. With regard to friendship quality, children with LD reported higher levels of conflict, lower levels of validation, and more problems with relationship repair than did children without LD. The findings were discussed in terms of factors that have been found to enhance friendship such as proximity and similarity, and the social skills difficulties that have been associated with learning disabilities.     

The Dental Subscale of the Children's Fear Survey Schedule: Predictive Value and Clinical Usefulness

This study reports on the predictive value and clinical usefulness of the Dutch parental version of the Dental Subscale of the Children's Fear Survey Schedule (CFSS-DS). Parents of 718 children (4–12 years) completed this CFSS-DS version before or during the child's visit. The dentist rated the child's dental fear during treatment on a 5-point Likert-type Scale from 1 (not afraid at all) to 5 (very afraid). Reliability analysis was performed, and correlation coefficients between the two measures were calculated. The reliability of the scale proved to be high (Cronbach's = .93) and significant correlation coefficients were found (r = .58 and r = .68, p < .01). The negative predictive value of the CFSS-DS was high (.96), whereas its positive predictive value was relatively low (0.41). It was concluded that the CFSS-DS might be of clinical value as a screening device of dental fear, whereas its predictive value of fearful behavior should not be overestimated.     

Rats use a sense of direction to alternate on T-mazes located in adjacent rooms

Lister hooded rats were trained on a forced-sample T-maze alternation task in an environment lacking spatial landmarks. An early study of spontaneous alternation on the T-maze had shown that rats use a "spatial sense" to select alternate maze arms across mazes. As this phenomenon may provide a useful tool for studying the neural substrates of a directional sense, we wished to confirm this finding on a different version of the T-maze task, with well-trained animals. We found that rats successfully selected the appropriate maze arm when the choice phase of the task was presented on a second maze, oriented in the same direction, and located in an adjacent room. However, choice performance fell to chance level when the second maze was oriented 90° relative to the first. This result suggests that the rats do not simply alternate turns across the two environments, but rather that they rely on a sense of direction that is carried across environments. Electronic Publication     

Dimensions of Early Childhood Behavior Problems: Stability and Predictors of Change from 18 to 30 Months

The prevalence, structure, stability, and predictors of change in early behavior problems were examined in a population-based sample of Norwegian children at 18 and 30 months of age (N = 750). A clear factor structure involving four dimensions emerged at both assessment times: Two factors were characterized by externalizing behaviors and were labeled Social Adjustment and Overactive-Inattentive; one factor tapped internalizing problems and was labeled Emotional Adjustment; and the fourth, related to general immaturity, was labeled Regulation. Specific patterns of child and family risk factors were associated with stability and change over the two time points for each factor. Children with stable problems had the most problematic characteristics on all significant predictors, followed by children with problems at one, but not both, time points. The data suggest that it is possible to identify risk factors for stable problems at 18 months, allowing some prediction of those children whose problems will persist over early childhood. Since specific risk factors emerged for specific types of behavior problems, the results may provide some much-needed guidance to early intervention efforts.     

One Frog, Two Frog, Red Frog, Blue Frog: Factors Affecting Children's Syntactic Choices in Production and Comprehension

Two experiments are reported which examine children's ability to use referential context when making syntactic choices in language production and comprehension. In a recent on-line study of auditory comprehension, Trueswell, Sekerina, Hill, and Logrip (1999) examined children's and adults' abilities to resolve temporary syntactic ambiguities involving prepositional phrases (e.g., “Put the frog on the napkin into ¨”). Although adults and older children used the referential context to guide their initial analysis (pursuing a destination interpretation in a one-frog context and a modifier interpretation in a two-frog context), 4 to 5-year olds' initial and ultimate analysis was one of destination, regardless of context. The present studies examined whether these differences were attributable to the comprehension process itself or to other sources, such as possible differences in how children perceive the scene and referential situation. In both experiments, children were given a language generation task designed to elicit and test children's ability to refer to a member of a set through restrictive modification. This task was immediately followed by the “put” comprehension task. The findings showed that, in response to a question about a member of a set (e.g., “Which frog went to Mrs. Squid's house?”), 4- to 5-year-olds frequently produced a definite NP with a restrictive prepositional modifier (e.g., “The one on the napkin”). These same children, however, continued to misanalyze put instructions, showing a strong avoidance of restrictive modification during comprehension. Experiment 2 showed that an increase in the salience of the platforms that distinguished the two referents increased overall performance, but still showed the strong asymmetry between production and comprehension. Eye movements were also recorded in Experiment 2, revealing on-line parsing patterns similar to Trueswell et al.: an initial preference for a destination analysis and a failure to revise early referential commitments. These experiments indicate that child–adult differences in parsing preferences arise, in part, from developmental changes in the comprehension process itself and not from a general insensitivity to referential properties of the scene. The findings are consistent with a probabilistic model for uncovering the structure of the input during comprehension, in which more reliable linguistic and discourse-related cues are learned first, followed by a gradually developing ability to take into account other more uncertain (or more difficult to learn) cues to structure.     

The Client Is the Most Important Common Factor: Clients' Self-Healing Capacities and Psychotherapy

I first briefly review the dodo bird verdict and suggest that we should be responding to it by looking for a new way to conceptualize how therapy works. Then I describe the dominant medical or treatment model of psychotherapy and how it puts the client in the position of a dependent variable who is operated on by supposedly potent therapeutic techniques. Next I argue that the data do not fit with this model. An alternative model is that the client is the most important common factor and that it is clients' self-healing capacities which make therapy work. I then argue that therapy has two phases—the involvement phase and the learning phase—and that the involvement phase is the most important. I next review the five learning opportunities provided by therapy. Finally, I argue that a relational model of therapy focused on consultation, collaboration, and dialogue is better than a treatment model.     

The variability of practice hypothesis in motor learning: does it apply to Alzheimer's disease?

Based on Schmidt's (1975) variability of practice hypothesis, this study examined acquisition and transfer of a gross motor skill, namely tossing, in 58 patients with Alzheimer's disease (AD) and 58 healthy older adults under constant, blocked, and random practice conditions. While healthy older adults were able to learn the tossing task equally well under the three practice conditions, only AD patients receiving constant practice showed significant improvements. Tests of intermediate transfer yielded the expected random practice advantage in healthy controls but not AD patients. None of the practice conditions facilitated intermediate transfer in AD patients; however, constant practice did benefit these impaired individuals on tests of near transfer. These results indicate that the variability of practice hypothesis does not extend to AD patients. As motor learning and transfer were clearly a function of constant practice, future attempts to retrain basic activities of daily living in AD patients should emphasize consistency in training.     

The role of inferences about referential intent in word learning: evidence from autism

Young children are readily able to use known labels to constrain hypotheses about the meanings of new words under conditions of referential ambiguity. At issue is the kind of information children use to constrain such hypotheses. According to one theory, children take into account the speaker's intention when solving a referential puzzle. In the present studies, children with autism were impaired in monitoring referential intent, but were equally successful as normally developing 24-month-old toddlers at mapping novel words to unnamed items under conditions of referential ambiguity. Therefore, constraints that lead the child to map a novel label to a previously unnamed object under these circumstances are not solely based on assessments of speakers' intentions.     

Interfering neighbours: the impact of novel word learning on the identification of visually similar words

We assessed the impact of visual similarity on written word identification by having participants learn new words (e.g. BANARA) that were neighbours of familiar words that previously had no neighbours (e.g. BANANA). Repeated exposure to these new words made it more difficult to semantically categorize the familiar words. There was some evidence of interference following an initial training phase, and clear evidence of interference the following day (without any additional training); interference was larger still following more training on the second day. These findings lend support to models of reading that include lexical competition as a key process.