Why walkers slip: shine is not a reliable cue for slippery ground

In a series of four studies, we investigated the visual cues that walkers use to predict slippery ground surfaces and tested whether visual information is reliable for specifying low-friction conditions. In Study 1, 91% of participants surveyed responded that they would use shine to identify upcoming slippery ground. Studies 2-4 confirmed participants' reliance on shine to predict slip. Participants viewed ground surfaces varying in gloss, paint color, and viewing distance under indoor and outdoor lighting conditions. Shine and slip ratings and functional walking judgments were related to surface gloss level and to surface coefficient of friction (COF). However, judgments were strongly affected by surface color, viewing distance, and lighting conditions--extraneous factors that do not change the surface COF. Results suggest that, although walkers rely on shine to predict slippery ground, shine is not a reliable visual cue for friction. Poor visual information for friction may underlie the high prevalence of friction-related slips and falls.     

Stimulating the demand for dental care: An application of Ajzen and Fishbein's theory of reasoned action

Ajzen and Fishbein's attitude-behaviour model was applied to the problem of stimulating the demand for dental care, Subjects were 329 members of Amsterdam health insurance companies. They had not received regular dental treatment and/or a certificate of dental fitness for at least two and a half years. Applying for treatment and acquiring a dental certificate were the behavioural measures. The effectiveness of the communication based on Ajzen and Fishbein's model was compared with the effectiveness of messages based on the Health-Belief model and the notion that knowledge of Rights and Obligations is a prerequisite for seeking dental care. Results lend support to the validity of the Ajzen and Fishbein model. Relationships between the components of the model are moderate to strong, both before and after subjects were exposed to the message. The message proved effective in changing beliefs about seeking dental treatment. Ajzen and Fishbein's claim that their approach has exclusive merits, however, was refuted. A differential effectiveness of the three messages was absent. In all, 47.4 per cent applied for treatment. No control subjects applied. Fifteen months later 70 per cent of the applicants had obtained a dental certificate. Contrary to our expectations, a condition of no-message application-form- only proved equally effective as the message conditions.     

One sound or two? Object-related negativity indexes echo perception

The ability to isolate a single sound source among concurrent sources and reverberant energy is necessary for understanding the auditory world. The precedence effect describes a related experimental finding, that when presented with identical sounds from two locations with a short onset asynchrony (on the order of milliseconds), listeners report a single source with a location dominated by the lead sound. Single-cell recordings in multiple animal models have indicated that there are low-level mechanisms that may contribute to the precedence effect, yet psychophysical studies in humans have provided evidence that top-down cognitive processes have a great deal of influence on the perception of simulated echoes. In the present study, event-related potentials evoked by click pairs at and around listeners' echo thresholds indicate that perception of the lead and lag sound as individual sources elicits a negativity between 100 and 250 msec, previously termed the object-related negativity (ORN). Even for physically identical stimuli, the ORN is evident when listeners report hearing, as compared with not hearing, a second sound source. These results define a neural mechanism related to the conscious perception of multiple auditory objects.     

Motor training at 3 months affects object exploration 12 months later

The development of new motor skills alters how infants interact with objects and people. Consequently, it has been suggested that motor skills may initiate a cascade of events influencing subsequent development. However, only correlational evidence for this assumption has been obtained thus far. The current study addressed this question experimentally by systematically varying reaching experiences in 40 three‐month‐old infants who were not reaching on their own yet and examining their object engagement in a longitudinal follow‐up assessment 12 months later. Results revealed increased object exploration and attention focusing skills in 15‐month‐old infants who experienced active reaching at 3 months of age compared to untrained infants or infants who only passively experienced reaching. Further, grasping activity after – but not before – reaching training predicted infants’ object exploration 12 months later. These findings provide evidence for the long‐term effects of reaching experiences and illustrate the cascading effects initiated by early motor skills.     

Women and Natural Hierarchy in Aristotle

In this paper, I examine the frame of reference in Aristotle's Politics within which he makes claims about women and their place in his conception of politics.     

Gauging possibilities for action based on friction underfoot

Standing and walking generate information about friction underfoot. Five experiments examined whether walkers use such perceptual information for prospective control of locomotion. In particular, do walkers integrate information about friction underfoot with visual cues for sloping ground ahead to make adaptive locomotor decisions? Participants stood on low-, medium-, and high-friction surfaces on a flat platform and made perceptual judgments for possibilities for locomotion over upcoming slopes. Perceptual judgments did not match locomotor abilities: Participants tended to overestimate their abilities on low-friction slopes and underestimate on high-friction slopes (Experiments 1-4). Accuracy improved only for judgments made while participants were in direct contact with the slope (Experiment 5), highlighting the difficulty of incorporating information about friction underfoot into a plan for future actions.