Diners paying with cash received either $1 or $6 of change over the correct amount; in 128 out of 192 tables, the diners did not return the excessive change; women returned the extra change much more often than men

The cost of being honest: Excessive change at the restaurant. Chp 4.2 in Dishonesty in Behavioral Economics - Perspectives in Behavioral Economics and the Economics of Behavior, 2019, Pages 267-288. Ofer H. Azar, Shira Yosef, Michael Bar-Eli. https://doi.org/10.1016/B978-0-12-815857-9.00015-7

Abstract: In a field experiment conducted in an Israeli restaurant, diners paying with cash received either 10 or 40 Shekels (about €2 or €8) of change over the correct amount. In 128 out of 192 tables, the diners did not return the excessive change. Women returned the extra change much more often than men, especially among repeated customers. Interestingly, a table with a woman and a man resembles a male table and not a female table. Repeated customers returned the excessive change much more often than one-time customers. Tables with two diners were not significantly more likely to return the excessive change than tables with one diner. We hypothesized that customers will return more often 10 extra Shekels than 40, but found a strong pattern in the opposite direction. This implies that in some situations the psychological cost of dishonest behavior increases more rapidly than the amounts involved.