The individual learning principle of cost equalization is used to acco
unt for the emergence of a reproducible power and influence structure
in dyadic interaction. This principle predicts that in situations in w
hich the outcomes of collective actions apply to the dyad rather than
to individuals, simultaneous dependent learning mechanisms will genera
te an inequitable and unequal power relation favoring the actor who ma
kes more attempts at influence. This hypothesis was tested with two di
fferent experiments: In both, the findings supported the cost-equaliza
tion model. The difference between these findings and others in the li
terature is attributed to our focus on dyads whose interaction structu
re permits spontaneous initiation of influence attempts.