The thinking/reasoning was pertaining to the construction of a psychological experiment, yes.
In a lab setting, it was noticed that subjects experience X during Y. It was suggested to inform the subjects that this is a correlated event, but the suggestion was rejected because it was thought that by being made aware of this potential relationship, the subjects would be more likely to report instances of X during Y, simply by virtue of knowing about the potential relationship.
Perhaps my wording "experience more strongly" was a poor choice; or perhaps it does not involve thinking/reasoning, as you say.
Consider "more likely to experience," though that may be equally ambiguous.
A notes X happens during Y.
A finds a correlation of this fact.
A then goes on to report more instances of X during Y simply because they are aware of the possibility that X occurs during Y.
I thought it might have been similar to the Historical Fallacy, or cum hoc ergo propter hoc, as I stated in the original question. Though I suppose I am mistaken.