Although previous research has shown that perceived objective similarity (Me-sharing) and perceived subjective similarity (I-sharing) both increase liking for strangers, perceived subjective similarity may have a unique effect on selflessness. Study 1 addressed this possibility by focusing on whether I-sharing (but not Me-sharing) promotes greater willingness to share a desired good. After interacting with three ostensible partners (an I-sharer, a Me-sharer, and a Not Similar Other), participants indicated their liking for each of these partners and distributed a desired good between themselves and each partner. Although participants reported higher liking for both the I-sharer and the Me-sharer than for the dissimilar other, when it came to the allocation of the desired good, they showed generosity only to the I-sharer. Study 2 addressed questions lingering from Study 1 by manipulating I-sharing and Me-sharing in a between participants design, by equalizing the importance of the I-sharing and Me-sharing dimensions, and by looking at a separate indicator of selflessness (i.e., helping intentions). Results conceptually replicated those of Study 1, with participants reporting significantly higher helping intentions when they I-shared with their partner than when they Me-shared with their partner (even though participants reported equivalent levels of liking in both partner conditions). Taken, together these findings suggest that subjective similarity contributes uniquely to a person's ability to behave selflessly.
Huneke, M., & Pinel, E. C. (2016). Fostering selflessness through I-sharing. Journal of Experimental Social Psychology, 63, 10–18. https://doi.org/10.1016/j.jesp.2015.11.003