Coin value and perceived size: a longitudinal study

Decimalization of the Irish currency presented an opportunity to study the perceived size of coins as they were introduced or withdrawn and to examine the accentuation of differences between coins. Estimates were obtained of the sizes of 4 coins from 478 subjects in 3 groups tested at different times: just after decimalization, 2, or 3 yr. later. A newly introduced coin was significantly underestimated in size at first but came to be significantly overestimated later, while all familiar coins were always significantly overestimated. The amount of overestimation of a coin depended on its value, not its size, leading to an accentuation of the difference between any two coins if the larger coin was also the more valuable but sometimes to the opposite if the smaller coin were of higher value than the larger member of the pair.