A visual bias for falling objects.

Aristotle believed that objects fell at a constant velocity. However, Galileo Galilei showed that when an object falls, gravity causes it to accelerate. Regardless, Aristotle's claim raises the possibility that people's visual perception of falling motion might be biased away from acceleration towards constant velocity. We tested this idea by requiring participants to judge whether a ball moving in a simulated naturalistic setting appeared to accelerate or decelerate as a function of its motion direction and the amount of acceleration/deceleration. We found that the point of subjective constant velocity (PSCV) differed between up and down but not between left and right motion directions. The PSCV difference between up and down indicated that more acceleration was needed for a downward-falling object to appear at constant velocity than for an upward "falling" object. We found no significant differences in sensitivity to acceleration for the different motion directions. Generalized linear mixed modeling determined that participants relied predominantly on acceleration when making these judgments. Our results support the idea that Aristotle's belief may in part be due to a bias that reduces the perceived magnitude of acceleration for falling objects, a bias not revealed in previous studies of the perception of visual motion.

Mental health among Vietnamese urban late adolescents: The association of parenting styles.

The aim of this study was to explore the correlation between parental styles and mental problems among Vietnamese high school students. In total, 16.4 percent of 757 eligible participants reported mental difficulties. Findings showed that being female and in grade 12 were risk factors to mental problems while living in Hue city was likely as a protective factor. The father's warmth reduced the risk of having mental problems among adolescents, while an overprotective mother increased the risk. There was no correlation between authoritarianism of both mother and father and mental difficulties. These results suggest that a parenting program for parents might reduce the risk of mental problems among Vietnamese youth.