What are friends for? The impact of friendship on communicative efficiency and cortisol response during collaborative problem solving among younger and older women.

Conversation is a skilled activity that depends on cognitive and social processes, both of which develop through adulthood. We examined the effects of age and partner familiarity on communicative efficiency and cortisol reactivity. Younger and older women interacted with familiar or unfamiliar partners in a dyadic collaborative conversation task (N = 8 in each group). Regardless of age, referential expressions among familiar and unfamiliar partners became more efficient over time, and cortisol concentrations were lower for speakers interacting with familiar partners. These findings suggest that communicative effectiveness is largely preserved with age, as is the stress-buffering effect of a familiar partner.