Changes in Muscle Activity in Response to Assistive Force during Isometric Elbow Flexion

Abstract

This study investigated the muscle activity and force variability in response to perturbation of assistive force during isometric elbow flexion. Sixteen healthy right-handed young men (age: 22.0?±?1.1?years; height: 171.9?±?4.8?cm; weight 68.4?±?11.2?kg) were recruited and the muscle activity of biceps brachii and triceps brachii were assessed using surface electromyography. Workload force and assistive force applied on isometric elbow flexion significantly affected the changes in both biceps and triceps muscle activities. A higher assistive force was shown to result in reduced biceps muscle activity compared to the unassisted period. In contrast, the efficiency of the assistive force acting on the biceps decreased as the assistive force increased. In general, the force variability of the biceps muscle remained approximately the same at lower workload force conditions than that at higher workload force conditions. In conclusion, higher assistive force may not yield a higher performance efficiency in human-assistive force interaction.     

Do 5- and 6-Year-Old Children Attempt to Appear Fair to Others?

Abstract

Children come to prefer fair distributions at the age of 5 to 6?years. But do they actually want to be fair, or do they want to appear fair to others? In three conditions, an experimenter initially distributed chocolates to 5-/6-year-old participants and partners they were paired with. Participants always possessed, through some means, two chocolates when the experimenter returned after a brief absence, and they had to decide whether to take an extra one for themselves. To measure the extent to which children were concerned with actually being fair versus appearing fair, two conditions were created in which children were led to believe that the experimenter did not know that the distributions had become equal. In the windfall condition, a confederate gave one additional chocolate to the participant, and in the partner condition, the partner transferred one chocolate to the participant. Compared to the control condition, participants who passed the false belief task in both of these conditions tried to appear fair in their distribution. Thus 5-/6-year-old children seem to prefer appearing fair to others regardless of the situation.     

Omission bias and perceived intention in children and adults

Omission bias refers to the tendency to judge acts of commission as morally worse than equivalent acts of omission. Children aged 7–8 and 11–12 years, as well as adults, made moral judgements about acts of commission and omission in two conditions in which the protagonist obtained a self‐directed benefit. In the antisocial condition, the other person was harmed; in the selfish condition, the other person was not harmed. The results showed that adults and both age groups of children judged that the agent who did something (act of commission) was morally worse than the agent who did nothing (omission) for both antisocial and selfish conditions, although this judgement tendency was clearer in the selfish condition than in the antisocial condition. Agent intention was held constant across commission and omission, but most participants rated the intention of the agent who did something as stronger than that of the agent who did nothing. These results suggest that omission bias occurs regardless of differences in age and situation. In addition, perceived intention appears to change in conjunction with omission bias.