The influence of motor system degradation on the control of handwriting movements: a dynamical systems analysis

The complex dynamics of the human hand/arm system need to be precisely controlled to produce fine movements such as those found in handwriting. This study employs dynamical systems analysis techniques to further understand how this system is controlled when it is functioning well and when it is compromised through motor function degradation (e.g. from tremor). Seven people with and 16 people without multiple sclerosis (MS) participated in this study. Tremor was assessed using spirography with participants being separated into "tremor" (6 people with and 1 person without MS; 2 male, 5 female; age range 40-68) and control (1 person with and 15 people without MS; 5 male, 11 female, age range 18-59) groups. Participants wrote the pseudo-word "lanordam" six times on a digitizer, in a quiet as well as a noisy, mildly stressful environment. Velocity profiles of the pen tip for the best four trials were concatenated and analyzed to determine their dimensionality (a measure of the number of control variables) and Lyapunov exponents (a measure of predictability). Results indicate that the velocity profiles for people with tremor were lower dimensional and had less predictable dynamics than for controls, with no effect of sound condition. Interpreted in the context of related research, it was speculated that the lower dimensionality reflected the loss of control of variables related to the minimization of movement variability, resulting in less predictable movements.     

Cognitive Heuristics and AIDS Risk Assessment Among Physicians1

Physicians (N= 331) reported perceived risk of HIV exposure, worry about on-the-job HIV exposure, and experience with patients who test seropositive for the HIV. In addition, the use of the availability heuristic was examined by responses to questions about talking and reading about AIDS, and the use of the simulation heuristic was examined by responses to questions about imagining oneself being exposed to HIV on the job. Simulation of the HIV-exposure experience related significantly to perceived risk (p < .001), even after variance attributable to actual experience and use of the availability heuristic was taken into account. Availability of AIDS information related marginally to perceived risk after variance attributable to actual experience and use of the simulation heuristic was taken into account. Simulation related strongly with worry about on-the-job exposure (p < .001), and availability was not significantly related to worry after variance associated with simulation and experience with AIDS was removed. Implications of these results for physician training are discussed.     

Response Time and Temporal Order Judgement in Vision

Both response proportion and response time (RT) measures were obtained in a task requiring temporal order judgements (TOJ) of the illumination of two lights. The decrease in mean RT as the inter-stimulus interval increased enabled the deterministic decision rule for TOJ to be rejected. Although the data were not inconsistent with a decision process incorporating a threshold for temporal resolution, a model based on a random walk process accounted for important features of the data. The implications of these results for the commonly employed “perceived-order” method are discussed.     

Dyadic processes of relational turbulence theory

This study tested dyadic processes of relational turbulence theory (RTT) in heterosexual marriages. We tested propositions 1, 2, and 5 of RTT, which propose that uncertainty about the marriage biases cognitive appraisals, and that interference from a partner heightens negative emotions, both of which culminate in relational turbulence for spouses. Guided by these propositions, husbands' and wives' (N = 510; 255 marital dyads) dyadic cognitive and emotional processes were estimated using the actor-partner interdependence mediation model. Consistent with theoretical propositions, we found evidence for actor-actor indirect effects; for both husbands and wives (a) the effect of spouses' relationship uncertainty on their own relational turbulence was mediated by their own biased cognitive appraisals, and (b) the effect of spouses' experienced interference on their own relational turbulence was mediated by their own anger from communicating in the marriage. However, controlling for actor-actor indirect effects, partner-defined processes (i.e., actor-partner and partner-actor indirect effects) uniquely explained husbands' and wives' relational turbulence.     

Imitative violence in the real world: A reanalysis of homicide rates following championship prize fights

Recently, Phillips [Am Soc Rev, 1983; 48:560–568] reported that the homicide rate increases on the third day after heavyweight championship prize fights. The present paper reports a reanalysis of Phillips's data using more sophisticated statistical techniques and examining several theoretically important variables not discussed by Phillips or his critics. Using a conservative analysis strategy, our results suggest that the increases in homicides reported by Phillips were not a methodological artifact as suggested by Baron and Reiss [Am Soc Rev 1985; 50:347–363, 372–376]. The homicide increases only occur on the first weekend or holiday after prize fights that receive the greatest publicity.     

Detecting nonlinearity in psychological data: Techniques and applications

Modern graphical and computational techniques for detecting nonlinearity in psychological data sets are presented. These procedures allow researchers to determine the information complexity of temporal data, using physiological and psychological measurements, and to provide evidence for chaos in time series contaminated by measurement noise. Problems with noise reduction and appropriate experimental control, using surrogate time series, are discussed, and applications of the technology are illustrated, using response time, handwriting, and typing data sets. In an experimental application of appropriate nonlinear analysis procedures, the results of a time series prediction experiment confirm that some subjects are sensitive to chaos. In contrast to previous attempts demonstrating sensitivity to chaos, the experiment reported here employs surrogate series to control for linear stochastic aspects of the stimulus sequences, such as autocorrelation. Recommendations for the selection of appropriate software for performing nonlinear analyses are presented, including a comprehensive list of World-Wide Web sites offering such software.     

Memory for kinesthetically defined target location: evidence for manual asymmetries

Sixteen right-handed male adults performed a pointing task without vision. The participant's arm was moved passively to one of four targets which was subsequently pointed to following a delay of 1, 2, or 10 s. Our previous research on visual memory for target location showed a rapid decay which was comparable for both hands. The present study of memory for kinesthetic target location found decay for the left hand only. These findings suggest two memory stores for target location information, one visual which decays over time but is accessible to both hands and another based on kinesthetic information which is more stable and limb specific.     

Surprise is predicted by event probability,outcome valence,outcome meaningfulness,and gender

The present research was designed to better understand how the magnitude of experienced surprise is affected by both individual difference variables as well as variations in surprise-eliciting stimuli. Eighty-five participants played 5 versions of a slot machine-like game. The five games only differed with respect to the probability of winning each trial—10 % (i.e., wins were highly unusual), 30, 50, 70, and 90 % (i.e., losses were highly unusual). Players were given a fictitious “bankroll” at the beginning of each game and played up to 25 trials of each game. On each trial, players selected their wager amount, “pulled” the handle, learned the outcome (win or loss), and reported their surprise level using a 1 (none) to 9 (extremely) Likert scale. Replicating past research, results revealed that self-reported surprise was inversely related to outcome probability and that wins were rated as more surprising than losses, even when wins and losses occurred at the same level of probability. Novel results include finding that larger wagers predicted greater felt surprise (regardless of outcome), and that women reported greater surprise to both wins and losses than men.