Open science advocates argue that publicly and freely available scientific manuscripts, data and code will have wide-reaching collective benefits. However, the adoption of open science practices may depend on the fit between researchers' perceptions of open science and the social dynamics of their field. For example, if researchers understand open science as primarily a means of cooperating with other researchers, its adoption may be faster and more effective among researchers who see their field as less competitive and less hierarchical. The present studies operationalize open science attitudes as plans to publicly share manuscripts/preprints, code, stimuli/instruments and data, as well as participants' perceptions of the importance of these practices. In Study 1, researchers perceived the social dynamics of their field (competition and hierarchy) as distinct from the traits of individuals in their field (warmth and competence). In Study 2, neither researchers' perceptions of social dynamics, nor their view of open science as motivated by cooperation, predicted their attitudes to open science practices. However, attitudes about open science were generally very positive among researchers who opt-in to a study about open science, limiting the variance to be explained. Moreover, people's self-reported motivations for sharing manuscripts and materials differed from their perceptions of why others share manuscripts and materials. Study 3 tested the same questions in an independent and more representative sample. Results of Study 3 agreed with results of Study 2: neither researchers' perceptions of social dynamics, nor their view of open science as motivated by cooperation, predicted their open science practices. Again, attitudes about open science were generally very positive among researchers even in this representative sample and people's self-reported motivations for sharing manuscripts and materials differed from their perceptions of why others share manuscripts and materials.