Left-digit bias in self-reported height

Abstract

Left-digit bias is a cognitive bias wherein individuals assess the magnitude of numbers by emphasizing the leftmost digit. For instance, people often perceive the difference between $9.99 and $10.00 larger than that between $10.00 and $10.01, given the distinct left digits in the former two numbers. This study associates self-reported height with this cognitive bias. Taller stature is frequently associated with desirable attributes such as higher earnings and leadership positions; individuals may aspire to be taller and, consequently, report a height greater than their actual measurement. We posit that this inclination is more pronounced when combined with left-digit bias. In other words, individuals whose actual height ends in nine, such as 169 cm, are more likely to report their height as 170 cm than individuals with an actual height of 170 cm who report it as 171 cm. To conduct this analysis, we used data from an annual health survey of adolescents in grades 7–12. Our findings indicate that male adolescents exhibit a left-digit bias in reporting their height, whereas female adolescents do not. We contribute to the literature by providing new evidence of left-digit bias.