A researcher was interested in finding out whether children's ability to exhibit self-control when offered unhealthy food changed with age. He asked parents of three-year-old, six-year-old, and nine-year-old children to bring their children into the laboratory, where they were allowed to eat as much candy, cookies, and cake as they wanted. The researcher then compared the amount of food eaten by children of the three different ages. This is an example of:

Cooperation among oligopolies runs counter to the public interest because it leads to underproduction and high prices. in an effort to bring resource allocation closer to the social optimum, public officials attempt to force oligopolies to compete instead of cooperating. consider the following scenario: suppose that the presidents of two auto manufacturing companies exchange text messages in which they discuss jointly raising prices on their new lines of hybrid suvs. this illegal communication would violate which of the following laws? the sherman antitrust act of 1890 the robinson–patman act of 1936 the celler–kefauver act of 1950 the clayton act of 1914