Upper bounds for Kruskal's stress

In this paper the relationships between the two formulas for stress proposed by Kruskal in 1964 are studied. It is shown that stress formula one has a system of nontrivial upper bounds. It seems likely that minimization of this loss function will be liable to produce solutions for which this upper bound is small. These are regularly shaped configurations. Even though stress formula two yields less equivocal results, it seems to be expected that minimization of this loss function will tend to produce configurations in which the points are clumped. These results give no clue as to which of the two loss functions is to be preferred.This study has been supported by the Nederlandse Organisatie voor Zuiver-Wetenschappelijk Onderzoek (Netherlands Organization for the Advancement of Pure Research), under grant 56-146.Comments by Willem Heiser and Frank Critichley have been very helpful.The second author presently is employed by the Netherlands Central Bureau of Statistics, Voorburg.     

Anxiety, perception, and control of heart rate

8 women and 8 men took Cattell's IPAT-anxiety questionnaire and later McFarland's test of ability to perceive heart activity. The second test involved subjects' tracking their own heart rates, then they enrolled in an EKG biofeedback session to evaluate ability to increase and decrease heart rate from subjects' resting baselines. At the end of the session each subject completed Blanchard, et al.'s questionnaire to specify the cognitive strategies used for heart-rate control. Heart rate, abdominal respiration rate, respiration amplitude, EEG percent power in theta, alpha, and beta bands were evaluated. Success of heart-rate decrease seemed to depend mainly on activity levels: the subjects who achieved high scores on the activity test decreased heart rate significantly better than did low scorers. The relationship between scores for perception of heart and increases in heart rate was nonsignificant: increased heart-rate seemed to depend on differences in respiration between the rest and periods of increase. The significant, negative correlation between trait anxiety and perceptions of heart activity suggested that anxiety affected subjects' ability to perceive heart rate. The theta EEG power of the right hemisphere was significantly higher in subjects scoring high than for those low in perception of heart activity. During heart-rate increase tasks subjects mainly reported use of 'arousal responses,' similarly during heart-rate decrease tasks they reported use of relaxation responses.     

Dyslexia: saccadic eye movements

This paper describes an extensive study of the parameters of saccadic eye movement in a group of 28 poor-reading children and a comparative normally reading group of 31 children. Ages ranged from 6.0 to 16.9 yr. Poor readers had normal intelligence but were lagging by at least two years in reading ability as compared to their peer age group. Parameters studied in refixation eye movements included saccadic latency, accuracy, velocity, and acceleration, as well as differences in latency for abduct and adduct movements. Shapes of saccades were also studied. It was shown that eye-movement performance in simple saccadic refixation was not distinguishably different for poor readers and normal readers, even though in reading, which requires higher processing, eye-movement characteristics are quite different. Maturational changes for various saccadic eye-movement parameters were also examined for the normal and poor reading groups.     

Dynamic balance of learning disabled and nondisabled children

This investigation assessed a difference in the dynamic balance abilities of 30 learning disabled and 30 nondisabled children of elementary-school age. Only distance traveled across the beam, a novel task, was significantly different between groups; no other effects were significant. Nondisabled subjects traveled further across the beam before losing balance than learning disabled children.     

Properties of the recombination of one-dimensional motion signals into a pattern motion signal.

We have examined the human ability to determine the direction of movement of a variety of plaid patterns. The plaids were composed of two orthogonal sine-wave gratings. When the plaid components are of unequal spatial frequency or sometimes of unequal contrast, observers judge the direction of movement incorrectly. In terms of the two-stage model of Adelson and Movshon (1982), these errors may result from either a misjudgment in the perceived speeds of each of the components or a failure in the combination of one-dimensional component movements into a coherent direction of motion of the two-dimensional plaid pattern, or both. A comparison of the perceived direction of motion of plaids with the relative perceived speeds of the plaid component gratings suggest that both failures occur, but in different circumstances. The relative perceived speed of the plaid components was measured with a spatial and a temporal forced-choice technique, the former leading to larger differences. Our results support the notion that the visual system decomposes a moving plaid into oriented components and subsequently recombines the component motions.     

Beyond sex differences: Family and occupational roles' impact on women's and men's dreams

The question addressed is: do recent changes in the occupational roles of women, with their indirect influence on men's lives, have an impact on the dreams of women and men? Three groups of parents (N=96) including in equal numbers, mothers at home, wage-earning mothers and fathers, kept a dream diary from which two dreams per dreamer were content analyzed. Assuming continuity between daytime and dream experiences, it was hypothesized that differences in manifest dream content would be a function of single versus dual role enactment, rather than sex. Contrary to predictions, statistical analyses performed on selected dream variables did not yield significant differences between groups for pleasant and unpleasant emotions, friendly interactions and aggression. Dream characters, and the concerns they reflect, were found to vary, though, according to social roles. Commitment to their family was reflected above all in the mothers' at home dreams, while commitment to their profession took precedence in those of the wage-earning mothers. Comparable commitment to work and family was found among the fathers. Findings suggest that as gender differences in waking life decrease, so may differences in dreams.     

Spouse involvement in the treatment of obsessive-compulsive patients

Twelve married obsessive-compulsive patients were randomly allocated to either selfcontrolled exposure or partner-assisted exposure. Treatment in both conditions consisted of homepactice.The results at the Post-test showed that both versions of exposure in vivo resulted in significant improvements but the partner-assisted group improved more. After a 1-month treatment-free period no significant differences between conditions were found due to a continuing improvement in the selfcontrolled exposure condition. Results were maintained at a 6-month follow-up.It was concluded that home-practice is a cost-effective treatment procedure for obsessive-compulsives and that couple training may be useful with selected patients.