The tendency to overestimate what is visible in a planar mirror amongst adults and children

Adults hold several mistaken beliefs about simple mechanical and optical phenomena. In particular, many adults believe that they would be able to see their own image in a mirror before they are in front of it. Similarly, they expect objects to become visible in mirrors before they actually do. This overestimation of what is visible is known as the early error (Bertamini, Spooner, & Hecht, 2003). It has been suggested that incorrect models about mechanics, and therefore erroneous beliefs, develop over time, as evidenced by good performance in young children (Kaiser, McCloskey, & Proffitt, 1986). With respect to knowledge about what is visible in mirrors we report the first developmental data. We confirmed an effect for prospective University students but found no evidence of any early error in children between the age of 5 and 11. This erroneous belief about mirrors develops during the later school years when people develop a system of beliefs based on experience.