Cooperative automated vehicles (AVs) bring the potential for better safety, efficiency, and energy-savings on the individual and system level. Yet, these benefits can only be achieved if people cooperate. In this study, we explored the effects of cooperative and reciprocal AVs on people's wellbeing, trust, and cooperation. We conducted a mixed-design study (n = 304), where participants experienced four types of social interactions as between-subject conditions: 1) all altruistic interaction; 2) all selfish interaction; 3) altruistic other vehicle, selfish ego AV; 4) selfish other vehicle, altruistic ego AV. We found people's well-being was highest when other vehicle is selfish and ego AV is altruistic; whereas people's trust was the highest when people experienced all altruistic interactions. Results suggested a design balance when evaluating people's attitudes towards AVs: altruistic AVs can promote people's trust, whereas when evaluating people's well-being, the presence of selfish AV s may be beneficial. Future studies could model the balance between the user optimal and system optimal control policies.