Online survey panelists are frequently characterized as “professional respondents” who’s survey participation is motivated by self-interested incentive-maximization. Little scientific evidence exists to evaluate such claims. This paper reports on two experiments testing hypotheses at the intersection of survey incentives and unit-response; hypotheses that contrast theories of “economic exchange” and “social exchange.” A random sample of online survey panelists were randomly assigned to conditions varying both cash incentive and length of survey. Participants did not systematically respond more, or satisfice less when promised a higher cash incentive. Nor did participants respond more to a prepaid versus promised incentive. The results provide little support for a one-dimensional–“professional respondents”–characterization of online panelist motivations.