Date of Award

Fall 2019

Degree Type

Open Access Dissertation

Degree Name

Psychology, PhD


School of Social Science, Politics, and Evaluation

Advisor/Supervisor/Committee Chair

William D. Crano

Dissertation or Thesis Committee Member

Jason T. Siegel

Dissertation or Thesis Committee Member

Allen Omoto

Dissertation or Thesis Committee Member

Antonis Gardikiotis

Terms of Use & License Information

Terms of Use for work posted in Scholarship@Claremont.

Rights Information

© 2019 Lori R. Manes


Research has shown that when a source proffers a message that is incongruent with its expected position on a topic, it can have an effect on the perceived trustworthiness of the communicator, the persuasiveness of the message, and the extent to which the receiver elaborates the message. However, research in this area has not been consistent. Questions remain as to whether sourcemessage incongruence enhances source trustworthiness, attitude change, or both, relative to source-message congruence. Focusing on an environmental risk management context involving the cleanup of a hazardous waste site, this research investigated how source-message incongruence influenced perceptions of source trustworthiness, attitude change, perceptions of risk, and support for risk management decisions, as well as the extent to which respondents elaborated the communicator’s message. Experiment 1 presented participants (N = 155) with message either in favor of a Superfund designation for the hazardous waste site (proenvironmental message position) or in opposition to a Superfund designation (pro-business message position). The source of the message was either the president of a local environmental advocacy group (environmental source) or the cleanup project manager from the company responsible for the contamination and cleanup (corporate source). Taking into account participants’ reported levels of environmental concern and political ideology, results indicated that incongruous messages for both sources were more effective in changing attitudes than congruent messages. However, source trustworthiness increased only in the condition in which the corporate source advocated an incongruent (pro-environmental) message position. When the environmental source advocated an incongruent (pro-business) message position, perceptions of trustworthiness significantly decreased. In a study similar to Experiment 1, Experiment 2 (N = 168) examined how source-message incongruence influenced participants’ cognitive elaboration, while taking into account environmental concern, political ideology, and need for cognition. It was expected that the incongruent source-message combinations would elicit significantly different levels of cognitive elaboration than messages of sources advocating congruous messages. Results found no significant interaction between source and message on cognitive elaboration. Contrary to expectations, respondents in the two incongruent source-message conditions did not differ significantly in self-reported cognitive elaboration compared to the two congruent conditions. Unexpectedly, a main effect for message type emerged. Regardless of the source, when the corporate message position was advocated, participants engaged in significantly more cognitive elaboration than when the environmental message position was advocated. Possible explanations for these results are discussed, as are implications for environmental risk communication practitioners.