More on least squares estimation of the transition matrix in a stationary first-order markov process from sample proportions data

Miller suggested ordinary least squares estimation of a constant transition matrix; Madansky proposed a relatively more efficient weighted least squares estimator which corrects for heteroscedasticity. In this paper an efficient generalized least squares estimator is derived which utilizes the entire covariance matrix of the distrubances. This estimator satisfies the condition that each row of the transition matrix must sum to unity. Madansky noted that estimates of the variances could be negative; a method for obtaining consistent non-negative estimates of the variances is suggested in this paper. The technique is applied to the hypothetical sample data used by Miller and Madansky.I am indebted to a referee for his thoughtful suggestions on content and style.     

What is the optimal position of low-frequency words across line boundaries? An eye movement investigation

When displaying text on a page or a screen, only a finite number of characters can be presented on a single line. If the text exceeds that finite value, then text wrapping occurs. Often this process results in longer, more difficult to process words being positioned at the start of a line. We conducted an eye movement study to examine how this artefact of text wrapping affects passage reading. This allowed us to answer the question: should word difficulty be used when determining line breaks? Thirty-nine participants read 20 passages where low-frequency target words were either line-initial or line-final. There was no statistically reliable effect of our manipulation on passage reading time or comprehension despite several effects at a local level. Regarding our primary research question, the evidence suggests that word difficulty may not need to be accounted for when determining line breaks and assigning words to new lines.     

Vocal indicators of facilitative interpersonal skills

The facilitative interpersonal skills (FIS) method uses simulations of difficult client moments as a test of helpers' ability to remain therapeutic in therapeutically stressful situations. A total of 135 participants completed the FIS task as part of a training in helping skills and provided verbal responses that were assessed by trained raters for interpersonal skills. Audio recordings of these verbal responses were then analysed acoustically for fundamental frequency (F0), spectral slope and F0 range. Mean F0 and F0 range were more highly associated with trained raters' ratings of FIS for female participants than for male participants, although F0 range was associated with FIS of both males and females. The results suggest that F0 is associated with FIS for females, especially the FIS items that are indicative of emotional expression and verbal fluency. Findings are discussed as possibly indicating that some expression of higher F0 in response to distressed client situations may be part of interpersonal skills, such that more skilled therapists respond to stressful client situations with a higher F0.     

FIXED-TIME SCHEDULES ATTENUATE EXTINCTION-INDUCED PHENOMENA IN THE TREATMENT OF SEVERE ABERRANT BEHAVIOR

We compared the effects of extinction (EXT) and fixed-time (FT) schedules as treatment for severe problem behavior displayed by 3 individuals with developmental disabilities. First, functional analyses identified the reinforcers maintaining aberrant behavior for all 3 individuals. Next, EXT and FT schedules were compared using a multielement design. During EXT, the reinforcer maintaining problem behavior was withheld. During FT, the reinforcers were presented response independently at preset intervals. Results showed that FT schedules were generally more effective than EXT schedules in reducing aberrant behavior. FT schedules may be used in situations when extinction-induced phenomena are problematic.     

Near-Death Experiences, Shamanism, and the Scientific Method

The first 20 years of near-death studies have thoroughly documented the existence of this phenomenon. The field of near-death studies appears to be evolving from a purely academic one to include an applied, clinical component. I discuss the overlap between shamanism and near-death experiences (NDEs) and suggest that the study of shamanism would be helpful in more fully understanding this phenomena and beginning the development of an applied methodology. Although it may be difficult to verify subjective accounts of NDEs and shamanic journeys, from a clinical stand-point it may not be necessary to do so in order to develop a technique that passes the test of scientific scrutiny.     

Is age kinder to females than to males?

To investigate possible gender differences in the patterns of age-cognition relations, a meta-analysis was conducted on the data from 25 studies (5,201 participants) by the second author and his collaborators. Gender and age differences consistent with prior reports were found, but there were few measures on which the age × gender interactions were significant. Although the majority of neuroimaging studies investigating gender differences in age-related atrophy and functional decline report greater age-related differences in males, the only significant interactions on the cognitive measures in this study (on measures of speed and reasoning) were in the direction of lesser age-related declines for males than for females.     

TouchStat: A Monte Carlo program for calculating sequential touching probabilities

A growing number of child cognition researchers are using an object-manipulation, sequential-touching paradigm to explore young children’s conceptual abilities. Within this paradigm, it is essential to distinguish children’s intracategory touching sequences from those expected by chance. The sequentialtouching approach is congruent with a permutation testing model of statistical inference and is best modeled by sampled permutations as derived from Monte Carlo procedures. In this article, we introduce a computer program for generating Monte Carlo sequential-touching simulations. TouchStat permits users to determine their own specifications to simulate sequential touching to category exemplars across a wide range of task parameters. We also present Monte Carlo chance probabilities for the standard two-category, four-exemplar task, with sequences up to 30 touches long. Finally, we consider broader applications of the TouchStat program.     

Increasing the benefits of eye-tracking devices in divided visual field studies of cerebral asymmetry

A wide range of methods has been proposed for ensuring central fixation in divided visual field studies of cerebral asymmetry. We present some of the problems associated with ensuring central fixation and argue that objectively monitoring fixation location with an eye-tracking device can provide the only accurate and, therefore, acceptable technique. However, the mere use of this equipment does not overcome all of the problems associated with controlling fixation location, and previous studies have overlooked the importance of providing feedback on fixation accuracy and the role of visual attention. We propose a straightforward method of accommodating both these influences in studies using eyetracking devices to control fixation location.     

A COMPARISON OF REINFORCER ASSESSMENT METHODS: THE UTILITY OF VERBAL AND PICTORIAL CHOICE PROCEDURES

We compared three methods of stimulus preference assessment for verbal children and specifically evaluated the utility of a verbal choice procedure for assessing relative reinforcer value. Using a token system, relative preference for five categories of reinforcers, representing 15 different stimuli, was assessed by three methods: a reinforcer survey, a verbal stimulus-choice questionnaire, and a pictorial stimulus-choice procedure. Results showed that the verbal and pictorial stimulus-choice assessments accurately identified high- and low-preference categories for 3 of 4 participants. Survey results alone often rated multiple categories as high preference, were less likely to identify low-preference categories, and were less likely to correspond with the results of a reinforcer assessment.