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.     

Automaticity: a theoretical and conceptual analysis

Several theoretical views of automaticity are discussed. Most of these suggest that automaticity should be diagnosed by looking at the presence of features such as unintentional, uncontrolled/uncontrollable, goal independent, autonomous, purely stimulus driven, unconscious, efficient, and fast. Contemporary views further suggest that these features should be investigated separately. The authors examine whether features of automaticity can be disentangled on a conceptual level, because only then is the separate investigation of them worth the effort. They conclude that the conceptual analysis of features is to a large extent feasible. Not all researchers agree with this position, however. The authors show that assumptions of overlap among features are determined by the other researchers' views of automaticity and by the models they endorse for information processing in general.     

Phonological coding in reading of deaf children: Pseudohomophone effects in lexical decision

The purpose of this study was to find new evidence for phonological coding in written word recognition among deaf Dutch children. A lexical decision task was presented to 48 severely and profoundly deaf children aged from 6 years 8 months to 13 years 5 months, and a control group of Grade 1 hearing children matched on written word recognition. Sixteen pseudohomophones were introduced, closely matched on orthographic similarity with 16 control pseudo-words. Both hearing children and deaf children made significantly more mistakes on pseudohomophones than on control pseudo-words. Although pseudohomophony effects were smaller for deaf than for hearing participants, the findings were taken as evidence that deaf children also used phonological coding during written word recognition.     

Cross-cultural consistency of coding the strange situation

This study tested whether or not cross-cultural differences in attachment classification distributions result from systematic differences in coding practices. First, we investigated whether or not the interactive scales have been scored consistently in several different cross-cultural samples. Second, the Richters, Waters, and Vaughn (1988) functions were applied to address the question of whether or not attachment classifications were consistently based upon the same pattern of interactive behaviors. Third, cross-cultural coding differences were described from a multivariate perspective. Data sets from seven investigators in six countries were available for analysis. Analyses on this “multinational data set” revealed that except for distance interaction, the interactive scales in the two reunion episodes were scored in accordance with the original coding rules. Furthermore, a good to reasonable agreement appeared to exist between the original classifications and those computed by the functions, except for infants older than 20 months of age. The multivariate principal component analysis showed that classification groups across cultures were more alike than cultures across classification groups. Our data showed, therefore, that attachment classifications have been consistently coded across cultures.