Leventhal, H., Singer, R., Jones, S., Effects of Fear and Specificity of Recommendation Upon Attitudes and Behavior, JPSP, 1965, 2, 20-29.
There is a debate as to whether arousing fear in subjects will help or hurt persuasion and resulting intentions to act. The researchers found in a previous study that high fear arousing techniques can make people more receptive to recommendations, and that communication that arouses more fear can be more persuasive.

Further studies have shown that the immediate availability for action and the subject's predisposition to the potential success of that action also have a big effect on whether people will act.

This experiment attempted to see if high-fear or low-fear communications had an effect, with the initial variable being whether the subjects were presented with a specific plan of action on how to act.

Procedure
Students were informational booklets (either high-fear arousing or low-fear arousing) explaining tetanus and the benefits of tetanus innoculations.. The condition with high-specificity of action got detailed plans and maps on how to get shots. The low-specificity were only told that shots were available.

After reading the booklets all students filled out questionnaires. They also noted which students actually went to the health service to get shots.

Results
The high-fear booklets did produce more anxiety as reported in the questionnaires. They also reported more intent to get shots than the low-fear group (but didn't follow up on it). Those who received more specific information on how to get shots were more likely to get them than those with less specific information (though no-one in a control group who didn't read the booklets but got the specific info went to get shots).

"The analysese to this point appear to indicate that fear arousal is sufficient to influence attitudes while both arousal stimuli and specific recommendations are needed for action."

The test basically shows that you must arouse a person to the benefits of a change and provide a clear path of action for that change to facilitate action.