Previously published studies concerning the social behavior of red-backed salamanders (Plethodon cinereus) reported that in the forest (1) some male-female pairs co-inhabit territories even during the summer noncourtship season, and that in laboratory experiments (2) these pairs act as if they are socially monogamous, (3) males aggressively punish female partners that become polyandrous, and (4) females aggressively punish male partners that become polygynous. Past studies suggest that males and females freely choose their pair-partners in the forest and that sexual intimidation functions to keep partners monogamous. However, this inference is based on several underlying assumptions, which we test in the present study. We performed a series of experiments using randomly established pairs to test the assumptions that ‘natural’ pairs are more than an effect of familiarity between individuals and that extended housing as ‘pairs’ in the laboratory does not account for pair-like behavior. We found no evidence that members of either sex punished the opposite sex when laboratory–created pairs were housed together for either five or 30 days. Therefore, we conclude that the ‘pair-like’ behavior of natural pairs represents more than familiarity and that extended housing together does not account for that behavior.