Wegner, D. M., & Schneider, D. J., Carter, S.R.III, & White, T.L., Paradoxical Effects of Thought Suppression, JPSP, 1987, 53, 636-647

Thought suppression seems to have the opposite effects and makes people fixate on it. Yet what happens when people make a conscious effort to avoid a particular thought? People seem to include information in judgements when they are told to ignore or disregard the information or when they are told the info is false.

The attempt to avoid thoughts may lead to a later preoccupation with such thoughts.

Procedure
Two groups were asked to verbalize for five minute periods. Some groups were first asked to verbalize without thinking about a white bear and should ring a bell if they do so. Others were given no such instruction. Later they were to verbalize about a white bear. Some were asked to verbalize about the bear first and then try to suppress it.

Results
People thought of the white bear about once per minute even when asked to suppress. Initial suppression seems to produce even more expression in the later verbalization period about the white bear. Bell rings per minute increased on ly in expression segments made by the initial suppression group. These folks had an accelerating tendency to report the thoughts when asked to verbalize about the white bear.

Thus supressing a thought produces a subsequent preoccupation with the thought. Thought suppression is hard. Supression is hard because the thought "not white bear" is not focused. Thinking about another thought becomes tiring, and then people ask themselves "What am I doing?" They are then reminded about the white bear.

However, during the supression all the things people think about become associated with the negative cue (white bear), creating more associations that can be used in the expression period.

Experiment 2
People were instructed to think about a red Volkswagen to avoid thinking about the white bear. Though they did think about the red Volkswagen, it did not affect the frequency of white bear thoughts. However in the expression phase the "rebound effect" was reduced by the prior positive cue.

It appears the focused-misdirection reduces the number of "not white bear" associations that affect subsequent expression frequenticies and fixations. Their findings support the idea that supression can have negative side effects.