Shopping trolleys (IMAGE) University of Würzburg Caption The shopping trolley often contains not only what is needed, but also things that are bought spontaneously. Psychologists have investigated how impulse purchases come about. Credit (Photo: University of Wuerzburg) Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.