Date of Award


Degree Name

Master of Arts


Experimental Psychology


Lawrence Cohn


Individuals frequently encounter two types of information when evaluating the risk of a vaccination: statistical evidence describing the frequency of positive and negative outcomes, and anecdotal evidence describing positive and negative personal experiences. The present study evaluated the relative importance of both types of evidence when considered simultaneously. We predicted that the presentation of even one negative anecdote would have an effect on the key risk information (the â??gistâ??) that subjects extracted from the statistical and anecdotal data. Self-generated twitter posts (tweets) and standard measures of perceived risk were used to test the latter prediction. The current findings partially supported our predictions. Negative anecdotal evidence weighed more heavily in the decision to be vaccinated against HPV than justified by base-rate evidence. Notably, anecdotal evidence did not impact perceived risk of experiencing a normal or bad reaction to the vaccine. These findings suggest that counteracting negative anecdotal information regarding the HPV vaccine found online may increase campaign efficacy.




Received from ProQuest

File Size

146 p.

File Format


Rights Holder

Candice Fawn Coffman