Prejudice and discrimination remain a major social problem. The main strategy for reducing prejudice is to encourage contact between different groups. This thesis examines a learning process that underlies such contact: instrumental learning. In this process, people learn from the consequences of their behaviour. How does this learning influence what people think of others? The experiments show that people learn not only from what they do, but also from what they do not do—and that these inactions have a negative influence on evaluations. Actions that are rewarded lead to the most positive assessments, and this effect even extends to how quickly people recognise positive emotions in others. Thus, instrumental learning not only influences evaluations but also social behaviour. In addition, information about personal characteristics determines whether someone is included in our decision-making, even when that information is not actually relevant. This effect was not found for information about social groups. The findings of this thesis underscore the negative consequences of inaction, but also the power of positive actions. They offer new insights for interventions that aim to understand and reduce prejudice.
Tjits van Lent obtained her Bachelor's degree in Psychology at Radboud University, followed by a Research Master's degree in Behavioural Science. During her studies, she participated in the interdisciplinary Honours programme and spent a semester in Stellenbosch, South Africa. After a period as a behavioural psychologist at a behavioural change agency in Nijmegen, she started her PhD research at the Behavioural Science Institute of Radboud University in 2020, under the supervision of Prof. Rob Holland, Prof. Harm Veling, Dr Gijs Bijlstra and Dr Erik Bijleveld. She completed her thesis in 2025. Tjits currently works as a postdoctoral researcher at the Department of Social, Health and Organisational Psychology at Utrecht University.