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Crystal D. Oberle, Michael K. McBeath; Differential effects of visual feedback in a ball-dropping task reflect a robust “Galileo bias”. Journal of Vision 2004;4(8):617. doi: 10.1167/4.8.617.
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This research examined the effects of naïve physics beliefs and visual feedback on performance at a ball-dropping task. A pilot questionnaire with 105 undergraduates revealed that many people hold what we call a “Galileo bias,” believing that all objects fall at the same rate, regardless of air resistance effects. The current experiment tested (1) whether participants employ a cognitive strategy such that their beliefs guide their actions, and (2) whether visual feedback enhances performance and corrects their misconceptions. On 27 trials, 50 undergraduates dropped one of three ball sets from a height of 10m, with the goal of both balls hitting the ground simultaneously. (Pre-experimental video analyses revealed that the large ball should be dropped before the small ball of equal mass, that the light ball should be dropped before the heavy ball of equal volume, and that the two equal-density balls varying in both volume and mass should be dropped at the same time.) Results indicate that close to 60% of participants exhibited a strong Galileo bias, dropping the balls of each set at the same time throughout the experiment. The remaining participants began the experiment with the belief that heavy objects fall faster than light ones: for the two sets of balls varying in mass, they initially dropped the light one before the heavy one. Many reported being shocked that the small, light and large, heavy balls seemed to fall at the same rate; and from the visual feedback on these trials with the equal-density balls, they modified their beliefs. Subsequently, they improved across trials with the equal-density set, but became worse with the same-sized light and heavy balls and showed no improvement with the same-weighted small and large balls. In sum, the surprisingly absent or negative effects of visual feedback in some cases reflect the robust nature of the naïve Galileo bias.
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