Covert visual orienting across the lifespan.

Three groups of 20 K–5th graders, 20 college students, and 20 older adults (mean age 72.8 yrs) were tested. The S's task was the speeded discrimination of "X" from "O", but of primary interest was the effect of a location cue that appeared prior to the target. Both an abrupt stimulus cue and a voluntary information cue were studied using response time measures. Eye movements were monitored to control for differences in the ability to maintain fixation. Exp 1 showed that in comparison with young adults, children were less able to sustain orienting over time, and senior adults required more time to use the cue. Exp 2 (using K–1st graders, 4th–5th graders, 20 college students, and 20 older adults) tested the relation between stimulus and information cues when they both occurred prior to a given target. All age groups were able to use information cues in the presence of conflicting stimulus cues, but young adults were better able to do so than either children or senior adults. Results are interpreted as support for the view that separate mechanisms underlie stimulus-based versus information-based spatial orienting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual search for size is influenced by a background texture gradient.

Research on the perception of texture gradients has relied heavily on the subjective reports of observers engaged in free-viewing. We asked whether these findings generalized to speeded performance. Experiment 1 showed that an important aspect of subjective perception—size constancy scaling with perceived distance—also predicted the speed of pop-out visual search for cylinders viewed against a texture gradient. Experiment 2 showed that this finding could not be attributed to the local contrast between search items and the background texture. Experiment 3 assessed the relative contributions of 2 separable dimensions of texture gradients—perspective (radial spreading) and comprcssion (foreshortening—finding them to be independent in the more rapid search conditions (long target among shorter distractors) but combined in their influence in the slower conditions (short target among longer distractors). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Severe bicycling injury risk factors in children and adolescents: A case–control study

Background

Bicycling is the most common cause of sports and recreation injury in children and adolescents; yet, there is limited evidence on the factors associated with severe bicycling injuries in youth.

Methods

Case–control study of injured bicyclists less than 18 years old seen in seven emergency departments (EDs) from May 2008 to October 2010. Cases were bicyclists hospitalized after their ED visit (severe injury). Controls were bicyclists seen and discharged from the ED (non-severe injury). Personal, environmental, and crash characteristics were collected by interview. Injury data were collected from medical charts. Crude and adjusted odds ratios (ORs) and 95% confidence intervals (CIs) from logistic regression were used to estimate the odds of hospitalization associated with risk factors. Multiple imputation techniques were employed to address missing data.

Results

There were 1470 participants including 119 cases. Those ages 13–17 had the highest proportion (23%) of severe injuries resulting from motor vehicle [MV] collision. In models including age, sex and MV collision, being male (OR: 2.02; 95% CI: 1.21–3.38), not wearing a helmet (OR: 2.18; 95% CI: 1.43–3.31) and MV collision (OR: 3.91; 95% CI: 2.26–6.78) were significant risk factors for severe injury. Riding on a paved surface (OR: 0.63; 95% CI: 0.41–0.97) and utilitarian (school, work) bicycling (OR: 0.44; 95% CI: 0.2–0.94) decreased injury risk. Results were similar, apart from utilitarian bicycling (OR: 0.49; 95% CI: 0.22–1.06), after imputation for missing data.

Conclusion

Bicycle–MV collisions increase severe injury risk in youth, and adolescents are often injured in these events. This suggests separating bicyclists from MVs or traffic calming strategies could improve safety.     

A linear temperature probe with a low power supply voltage

A new principle of arranging temperature measurements in integrated temperature probes is suggested that makes it possible to attain a high linearity in a simple way. Circuitry implementation and techniques that allow one to reduce power supply voltage are considered. The experimental results obtained are given.     

The bicycle illusion: Sidewalk science informs the integration of motion and shape perception.

The authors describe a new visual illusion first discovered in a natural setting. A cyclist riding beside a pair of sagging chains that connect fence posts appears to move up and down with the chains. In this illusion, a static shape (the chains) affects the perception of a moving shape (the bicycle), and this influence involves assimilation (averaging) rather than opposition (differentiation). These features distinguish the illusion from illusions of motion capture and induced motion. The authors take this bicycle illusion into the laboratory and report 4 findings: Na?ve viewers experience the illusion when discriminating horizontal from sinusoidal motion of a disc in the context of stationary curved lines; the illusion shifts from motion assimilation to motion opposition as the visual size of the display is increased; the assimilation and opposition illusions are dissociated by variations in luminance contrast of the stationary lines and the moving disc; and the illusion does not occur when simply comparing two stationary objects at different locations along the curved lines. The bicycle illusion provides a unique opportunity for studying the interactions between shape and motion perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fluid and electrolyte hormonal responses to exercise and acute plasma volume expansion

To investigate the effect of acute graded increases in plasma volume (PV) on fluid and regulatory hormone levels, eight untrained men (peak aerobic power 45.2 +/- 2.2 ml.kg-1.min-1) performed prolonged cycle exercise (46 +/- 4% maximal aerobic power on three occasions, namely, with no PV expansion (Con) and after 14% (Low) and 21% (High) expansions, respectively. The exercise plasma levels of aldosterone (Aldo), arginine vasopressin (AVP), and atrial natriuretic peptide (ANP) were all altered by acute PV increases. A pronounced blunting (P < 0.05) of the Aldo response during exercise was observed, the magnitude of which was directly related to the amount of hypervolemia (Con < Low < High). At 120 min of exercise, Aldo concentrations were 660 +/- 71, 490 +/- 85, and 365 +/- 78 pg/ml for Con, Low, and High conditions, respectively. In contrast, the lower AVP and the higher ANP observed during exercise appeared to be due to the effect of PV expansion on resting concentrations. Because osmolality did not vary among conditions, the results indicate that PV represents an important primary stimulus in the response of Aldo to exercise. The lower exercise blood concentrations of both epinephrine and norepinephrine observed with PV expansion would suggest that a lower sympathetic drive may be implicated at least in the lower Aldo responses.     

Sparsity-enhanced network reduction for fault studies

A new short-circuit equivalent and reduction program is described that uses the adaptive reduction technique in which extra path nodes are retained to produce a sparser equivalent network. Nodes that may be reduced are chosen by flexible set formation facilities, with path nodes automatically retained as required to preserve sparsity. Tests on typical systems show that the sparsity-enhanced reduction produces an equivalent with fewer branches and a much lower branch-to-node ratio than conventional reduction for a wide range of numbers of nodes eliminated. At some point, as the number of retained nodes becomes small, conventional reduction produces an equivalent with fewer branches     

Section 1: Perception et action.

Introduces the first section of this issue of the Canadian Journal of Experimental Psychology. A question often on the minds of Cognitive Neuroscientists these days concerns the relation between perception and action. Those who are outside the field of perception may be excused for thinking that this must have always been so. This section begins with a paper by Flanagan, King, Wolpert, and Johansson examining the role of long-term memories in participants' adaptation to a size-weight illusion. The paper by Glover and Dixon examines the online control of action using a visual illusion in which the orientation of a background grating influences the perceived orientation of a foreground bar that must be grasped by the hand. The paper by Fecteau, Chua, Franks, and Enns is also concerned with the on-line control of action, but this time using a finger pointing task made popular by Goodale and colleagues. The final paper in this section by James, Humphrey, and Goodale comes full circle in that it examines how perception is influenced by action, rather than the other way around. If the four papers included in this section are at all representative of the state of Canadian research on Perception and Action, then the next few years will be interesting and productive ones indeed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)