Born to adapt, but not in your dreams

The brain adapts to changes that take place in the body. Deprivation of input results in size reduction of cortical representations, whereas an increase in input results in an increase of representational space. Amputation forms one of the most dramatic disturbances of the integrity of the body. The brain adapts in many ways to this breakdown of the afferent–efferent equilibrium. However, almost all studies focus on the sensorimotor consequences. It is not known whether adaptation takes place also at other “levels” in the system. The present study addresses the question whether amputees dream about their intact body, as before the amputation, or about the body after the amputation and whether the dream content was a function of time since the amputation and type of amputation. The results show that the majority of the dreamers reported dreams about their intact body although the mean time that elapsed since the amputation was twelve years. There is no clear relation with the type of amputation. The results give modest evidence for the existence of a basic neural representation of the body that is, at least, partly genetically determined and by this relatively insensitive for changes in the sensory input.     

Attachment anxiety,intra‐group (dis)respect,actual efforts,and group donation

The current study examines attachment‐style differences in responses to inductions of group respect and disrespect. Participants completed a scale assessing attachment anxiety and avoidance, performed group tasks, and received high, average, or low respect feedback from group members. Then we assessed commitment to this group, actual effort expenditure on behalf of the group, and money donation to the group. For participants scoring relatively high on attachment anxiety, high group respect heightened group commitment and effort expenditure on behalf of the group, whereas group disrespect led to lower group commitment but to more money donation to the group and higher effort expenditure. Participants who scored relatively low on attachment anxiety were not significantly affected by group respect or disrespect. The implications of attachment theory for group dynamics were discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Matching of visual input to only one item at any one time

When we perform a visual search we know what we are looking for and determine where it is. A representation of the object in our working memory, the ‘search-template’, is compared to the items in the scene until a match is found. So far it is unknown whether observers can search for multiple items at the same time. Here we compare the performance of subjects between a task in which they search for one of two target-items in a stream of visual objects and a task with only a single target. We find that search is effectively limited to one item at a time. This limitation occurs for simple and complex objects and even if the subjects have to look for two features from different domains. We conclude that matching has a fundamental capacity-limitation as the visual input can be matched to only one search-template at a time.     

Fixation identification: The optimum threshold for a dispersion algorithm

It is hypothesized that the number, position, size, and duration of fixations are functions of the metric used for dispersion in a dispersion-based fixation detection algorithm, as well as of the threshold value. The sensitivity of the I-DT algorithm for the various independent variables was determined through the analysis of gaze data from chess players during a memory recall experiment. A procedure was followed in which scan paths were generated at distinct intervals in a range of threshold values for each of five different metrics of dispersion. The percentage of points of regard (PORs) used, the number of fixations returned, the spatial dispersion of PORs within fixations, and the difference between the scan paths were used as indicators to determine an optimum threshold value. It was found that a fixation radius of 1° provides a threshold that will ensure replicable results in terms of the number and position of fixations while utilizing about 90% of the gaze data captured.     

EFFECTS OF A MULTIFACETED TRAINING PROCEDURE ON THE ACQUISITION AND GENERALIZATION OF SOCIAL BEHAVIORS IN LANGUAGE-DISABLED DEAF CHILDREN

Effects of a multifaceted training procedure were assessed on the acquisition and generalization of social behaviors with 9 language-disabled deaf children. The training procedure consisted of (a) child training and (b) supervision, feedback, and goal setting directed by teachers and residential staff. Target behaviors were turn waiting, initiating interaction, and interacting with others. Procedures to promote generality of effects and to determine the social validity of the procedures were used. Data were collected within a multiple baseline design across behaviors. Results showed a functional relationship between introduction of the training procedure and increases in percentage of appropriate target behaviors for all 9 children. The effects were maintained throughout a 5- to 10-week follow-up period.     

Ordinal data,ordered scale points,and order statistics

This paper concerns ordinal responses. An ordered Dirichlet distribution describes prior and posterior beliefs about the cumulative probabilities of response categories. Associating the response categories with intervals of a latent random variable then induces a distribution on the order statistics of that variable. The psychometrician can use the asymptotic theory of order statistics to learn how distributional assumptions about the latent variable effect inference. An example relates the skewness of a latent variable to the proportional odds and proportional hazards models of McCullagh [1980].     

Nosology and Causal Necessity; The Relation BetweenDefining a Disease and Discovering its Necessary Cause

The problem of disease definition is related to theproblem of proving that a certain agent is thenecessary cause of a certain disease. Natural kindterms like rheumatoid arthritis and AIDS refer toessences which are discoverable rather thanpredeterminate. No statement about such diseases isa priori necessarily true. Because theories onnecessary causes involve natural kind semantics,Koch's postulates cannot be used to falsify or verifysuch theories. Instead of proving that agent A is thenecessary cause of disease D, we include A in atheoretical definition of D, take this to representthe real meaning of D, and discard thepretheoretical definition. This is illustrated byKoch's own attempt to prove he had discovered thenecessary cause of tuberculosis. Methodologicalarguments about disease causation require a clear viewof our use of diagnostic terms. Medical lexicographersshould do more to provide such a view.     

Sequential estimations of time

Sequential estimations of intervals stored and reproduced by either counting or not counting are compared in experiments with single and repeated presentation of the standard interval. In a non-counting condition the estimates show a negative correlation with the last occurring trial throughout the series after one presentation of the standard. Consequently, in an ongoing process the capacity for (the storage and) the recall of time appears to be limited to the most recent event corresponding with the previous estimate. Correlations are lacking when the standard is presented after every estimate because the most recent information is an external constant. The correlations with the last trial recur when relatively long intervals are used, stored on the basis of various sensory cues. When the difference between the number of these cues is minimized, the correlation disappears. Counting never shows sequential correlations since it favors the coding and storage of time as a number of subjective units. The temporal equivalent of that number is constructed from trial to trial, a representation of the complete interval is not available and the subject does not remember his counting rate.     

Dynamic structural systems under indirect observation: identifiability and estimation aspects from a system theoretic perspective

In this—partly—expository paper the parameter identifiability and estimation of a general dynamic structural model under indirect observation will be considered from a system theoretic perspective. The general dynamic model covers (dynamic) factor analytic models, (dynamic) MIMIC models and Jöreskog's linear structural model as special cases. Its reduced form is—under a slightly different specification—known in system theory and econometrics as the stochastic, stationary version of the state-space model. By using concepts and methods from system theory, such as the observability and controllability concept, the (steady-state) Kalman filter and a general nonlinear ML_estimation procedure known as prediction-error estimation the general dynamic model will be identified. It will be shown that Jöreskog's LISREL-procedure is a special case of the prediction-error estimation procedure.