Purpose Co-operative managers must invest appropriately to strengthen member relationships, such as by initiating corporate social responsibility (CSR) actions or providing members with more relational benefits. This paper aims to investigate how members’ motives (collectivistic vs individualistic) might influence the effectiveness of these investments in terms of enhancing members’ trust and loyalty intentions. Design/methodology/approach This research combines an exploratory approach, based on six focus groups, with a confirmatory approach based on a field study and two scenario-based experiments. Findings Members tend to regard the two motives in contest and infer a “more CSR versus more benefits” arbitration effort by co-operatives, such that they appear to prioritize one motive over the other. Members with individualistic motives principally support co-operatives’ arbitration toward relational benefits, so the positive effects of CSR initiatives on their trust and loyalty intentions are weaker (Study 1). Both CSR and relational benefits can be more or less efficient, depending on members’ motives (Study 2). Research limitations/implications Reflecting their contrasting motives, members infer arbitration by co-operative managers, reflected in their “more CSR versus more benefits” belief. This insight and the related implications for trust and loyalty intentions have not been addressed in prior research. Practical implications Managers can avoid the negative consequences of “more CSR versus more benefits” inferences by ensuring a good fit between their investments and their members’ prevailing motives. If members have more collectivistic (cf. individualistic) motives, CSR initiatives (cf. relational benefits) enhance their trust and loyalty intentions more effectively. Originality/value This research builds on previous work on members’ relationships within co-operatives and on members’ motives. Results find that the effectiveness of co-operatives’ investments to strengthen members’ loyalty intentions depends on members’ prior motives.