Sensitivity of muscle force estimates to variations in muscle-tendon properties

The aim of this study was to determine the sensitivity of muscle force estimates to changes in some of the parameters which are commonly used to describe models of muscle-tendon actuation. The sensitivity analysis was performed on three parameters: optimal muscle-fiber length, muscle physiological cross-sectional area (PCSA), and tendon rest length. The muscles selected for the analysis were posterior gluteus medius/minimus, vasti, soleus, and sartorius. Each parameter was perturbed from its nominal value, and an optimization problem was solved to determine the relative influence of each parameter on the calculated values of muscle force. Muscle forces were calculated for a simulated cycle of normal walking. Parameter sensitivity was quantified using two new metrics: an integrated sensitivity ratio, which quantified the effect of changing a single parameter for any muscle on the time history of force developed by that muscle; and a summed cross-sensitivity ratio, which quantified the effect of changing one parameter for any muscle on the time histories of forces developed by all of the other muscles. The results showed that muscle force estimates for walking are most sensitive to changes in tendon rest length and least sensitive to changes in muscle PCSA. For soleus, for example, the integrated sensitivity ratios for tendon rest length were an order of magnitude greater than those for muscle-fiber length and PCSA. For vasti, the integrated sensitivity ratios for tendon rest length were twice as large as those for muscle-fiber length and nearly an order of magnitude greater than those for PCSA. Overall, changes in the tendon rest lengths of vasti and soleus and changes in the fiber length of vasti were most critical to model estimates of muscle force. Our results emphasize the importance of obtaining accurate estimates of tendon rest length and muscle-fiber length, particularly for those actuators that function as prime movers during locomotion (gluteus maximus, gluteus medius/minimus, vasti, soleus, and gastrocnemius).     

The perils of learning to move while speaking: One-sided interference between speech and visuomotor adaptation

Psychonomic Bulletin & Review - Our understanding of the adaptive processes that shape sensorimotor behavior is largely derived from studying isolated movements. Studies of visuomotor...     

Play enhances visual form perception in infancy–an active training study

Motor experiences and active exploration during early childhood may affect individual differences in a wide range of perceptual and cognitive abilities. In the current study, we suggest that active exploration of objects facilitates the ability to process object forms and magnitudes, which in turn impacts the development of numerosity perception. We tested our hypothesis by conducting a preregistered active exploration intervention with 59 8‐month‐old infants. The minimal intervention consisted of actively playing with and exploring blocks once a day for 8 weeks. In order to control for possible training effects on attention, we used book reading as a control condition. Pre‐ and post‐test assessments using eye‐tracking showed that block play improved visual form perception, where infants became better at detecting a deviant shape. Furthermore, using three control tasks, we showed that the intervention specifically improved infants' ability to process visual forms and the effect could not be explained by a domain general improvement in attention or visual perception. We found that the intervention did not improve numerosity perception and suggest that because of the sequential nature of our hypothesis, a longer time frame might be needed to see improvements in this ability. Our findings indicate that if infants are given more opportunities for play and exploration, it will have positive effects on their visual form perception, which in turn could help their understanding of geometrical concepts.     

Information from multiple modalities helps 5‐month‐olds learn abstract rules

By 7 months of age, infants are able to learn rules based on the abstract relationships between stimuli ( Marcus et al ., 1999 ), but they are better able to do so when exposed to speech than to some other classes of stimuli. In the current experiments we ask whether multimodal stimulus information will aid younger infants in identifying abstract rules. We habituated 5‐month‐olds to simple abstract patterns (ABA or ABB) instantiated in coordinated looming visual shapes and speech sounds (Experiment 1), shapes alone (Experiment 2), and speech sounds accompanied by uninformative but coordinated shapes (Experiment 3). Infants showed evidence of rule learning only in the presence of the informative multimodal cues. We hypothesize that the additional evidence present in these multimodal displays was responsible for the success of younger infants in learning rules, congruent with both a Bayesian account and with the Intersensory Redundancy Hypothesis.     

The relationship of GMA to counterproductive work behavior revisited

Recent research reported that general mental ability (GMA) predicted counterproductive work behavior (CWB), whereas some previous studies failed to find such a relationship. We tested occupational homogeneity of the sample and criterion measurement as two potential explanations for these inconsistencies. Study 1 replicated major design features of one previous study, which found no GMA–CWB relation in a heterogeneous sample, with occupationally homogeneous groups. Results confirmed previous null findings, indicating no effect of sample homogeneity. In Study 2, using a controlled laboratory setting, GMA was again unrelated to self‐reported CWB, but partially predicted observed CWB negatively. Combined findings suggest that GMA is consistently unrelated to CWB self‐reports but may predict objectively measured CWB independently of the likelihood of being caught. Copyright © 2009 John Wiley & Sons, Ltd.     

IQ in childhood and the metabolic syndrome in middle age: Extended follow-up of the 1946 British Birth Cohort Study

IQ in early adulthood has been inversely associated with risk of the metabolic syndrome in midlife. We tested this association in the British 1946 birth cohort, which assessed IQ at age eight years and ascertained the metabolic syndrome at age 53 years based on modified (non-fasting blood) ATPIII criteria. Childhood IQ was inversely associated with risk of the metabolic syndrome, but this association was almost entirely mediated by educational attainment and achieved occupational social class. This may be consistent with a pattern where childhood IQ is strongly associated with outcomes that reflect neurological disorder, such as the degenerative dementias, but less so with common chronic physical diseases of ageing.     

A COMPARISON OF PEER VIDEO MODELING AND SELF VIDEO MODELING TO TEACH TEXTUAL RESPONSES IN CHILDREN WITH AUTISM

Peer video modeling was compared to self video modeling to teach 3 children with autism to respond appropriately to (i.e., identify or label) novel letters. A combination multiple baseline and multielement design was used to compare the two procedures. Results showed that all 3 participants met the mastery criterion in the self‐modeling condition, whereas only 1 of the participants met the mastery criterion in the peer‐modeling condition. In addition, the participant who met the mastery criterion in both conditions reached the criterion more quickly in the self‐modeling condition. Results are discussed in terms of their implications for teaching new skills to children with autism.     

Retracted: Correction or comparison? The effects of prime awareness on social judgments

In previous research on the effects of accessible information on social judgments, divergent explanations have been offered for contrast effects that occur as a consequence of prime awareness. Some authors favor a comparison explanation, whereas others favor a correction explanation. In two studies, we successfully disentangled comparison and correction contrast by demonstrating that whereas correction for unwanted influences is a general process that leads to contrast on various dimensions on which a target is judged, comparison effects are prime specific and occur mainly on comparison relevant dimensions. In addition, our findings indicate that for correction attempts to occur and succeed, respondents must have the feeling that these primes contaminate their target judgments and should be removed from their “true” reaction to the target. When people are not suspicious of the potential contaminating influences of priming stimuli, prime awareness is more likely to lead to prime‐target comparisons than to correction efforts. Copyright © 2009 John Wiley & Sons, Ltd.     

The Resurgence of Anti-Semitism on American College Campuses

Few American college campuses have witnessed the number and intensity of anti-Semitic incidents reported at San Francisco State University, Columbia University, and the University of California at Irvine (2000–2005), however, dozens of American campuses every year experience at least some manifestation of this ugly problem, which is now undoubtedly national in scope. The Anti-Defamation League (ADL) documents nearly 100 anti-Semitic incidents on American college campuses in 2005 alone. Most incidents are probably not reported to the ADL. The United States Commission on Civil Rights monitors anti-Semitic incidents on college campuses and will continue to do so.