When preschool-aged children are presented with two objects, one familiar and one unfamiliar, and asked for the referent of a novel word, they will consistently map the novel word to the novel object, a tendency called the disambiguation effect. In this study, we examined the relation between vocabulary size and the disambiguation response tendency during late infancy. Sixteen-to 22-month-old infants were presented with a novel object along with two familiar objects and asked to choose the referents of familiar and novel words. The infants who consistently chose the novel object in the presence of a novel word had significantly higher productive vocabularies than those who did not. These two groups, however, did not differ in age or on familiar word trials.These results suggest that emergence of the disambiguation effect in late infancy is related to productive vocabulary size rather than age.Young children are amazingly adept word learners. Between the ages of 18 months and 6 years, children acquire approximately five to six new *

With more than 29,000 OpenSim users, several musculoskeletal models with varying levels of complexity are available to study human gait. However, how different model parameters affect estimated joint and muscle function between models is not fully understood. The purpose of this study is to determine the effects of four OpenSim models (Gait2392, Lower Limb Model 2010, Full-Body OpenSim Model, and Full Body Model 2016) on gait mechanics and estimates of muscle forces and activations. Using OpenSim 3.1 and the same experimental data for all models, six young adults were scaled in each model, gait kinematics were reproduced, and static optimization estimated muscle function. Simulated measures differed between models by up to 6.5° knee range of motion, 0.012 Nm/Nm peak knee flexion moment, 0.49 peak rectus femoris activation, and 462 N peak rectus femoris force. Differences in coordinate system definitions between models altered joint kinematics, influencing joint moments. Muscle parameter and joint moment discrepancies altered muscle activations and forces. Additional model complexity yielded greater error between experimental and simulated measures; therefore, this study suggests Gait2392 is a sufficient model for studying walking in healthy young adults. Future research is needed to determine which model(s) is best for tasks with more complex motion.

Search for a ball that has undergone hidden motion rapidly improves during the second year of life (Dev. Psychol., 2000; 36:394-401). In three experiments we investigated whether the poor performance of younger toddlers was due to attentional failure by highlighting the major cue for the hidden object. We observed only slight improvement in search behaviour. We performed two other experiments that tested the depth of understanding of 3-year-olds in this task and found that their performance was robust to changes in the apparatus and experimental procedures. Overall, the results point to a rapidly developing ability in the second year of life to either reason about space or select the correct motor response in search tasks.

The aim of this research -was to examine whether infants at the early stages of lexical development were sensitive to the word-category linkage. In Experiment 1,16-to 19-month-old infants were requested to match a target with either a basic-level or a thematic match, with or without a novel label. Stimuli were presented using the preferential looking paradigm. Infants in the Novel Label condition looked significantly longer at the basic-level match than infants in the No Label condition. In Experiment 2, infants •were presented with a target, followed by a basic-level match and a superordinate-level match with or without a novel label. Again, infants in the Novel Label condition looked significandy longer at the basic-level match than infants in the No Label condition. Taken together, these findings indicate that infants initially assume that novel words label basic-level categories and thereby do honour die word-category linkage.

Thirty-five percent of people above age 65 fall each year, and half of their falls are associated with tripping: tripping, an apparently 'mundane' everyday problem, therefore, significantly impacts on older people's health and associated medical costs. To avoid tripping and subsequent falling, sufficient toe clearance during the swing phase is crucial. We previously found that a rocker-shaped shoe sole enhances toe clearance in young adults, thereby decreasing their trip-risk. This study investigates whether such sole design also enhances older adults' toe clearance, without inadvertently affecting their walking stability. Toe clearance and its variability are reported together with measures of walking stability for twelve older adults, walking in shoes with rocker angles of 10°, 15°, and 20°. Surface inclinations (flat, incline, decline) were chosen to reflect a potential real-world environment. Toe clearance increased substantially from the 10° to the 15° rocker angle (p=0.003) without compromising measures of walking stability (p>0.05). A further increase in rocker angle to 20° resulted in less substantial enhancement of toe clearance and came at the cost of a decrease in gait speed on the decline. The novelty of this investigation lies in the exploration of the trade-off between reduction of trip-risk through footwear design and adverse effects on walking stability on real-life relevant surfaces. Our two studies suggest that the current focus on slip-resistance in footwear design may need to be generalised to include other factors that affect trip-risk.