With Sadness Comes Accuracy; With Happiness, False Memory
"In two experiments, we found that affect can influence the encoding processes believed to lead to the production of false memories. In particular, negative affective cues reduced the false memory effect."
…that positive affect can be expected to benefit performance on tasks requiring relational processing, but that negative affect may benefit performance on tasks requiring referential processing. In the present task, the referential processing of negative moods led to accuracy, whereas the relational processing of positive moods led to false memories.
I sat down with the author of this study yesterday. This is one of the first articles he did laying the ground work for his more recent research on how people who report being sad have better spacial recall and those who report being happy have better verbal recall.