Performance on spatial tests is not only a matter ability; it is also influenced by peoples confidence and belief of ability.Although we know that training can improve spatial performance, we know relatively little about the influences of beliefsand expectations on the efficacy of training. Here we investigated men and womens performance on a mental rotationtask and their prediction of their performance. We also examined whether providing information about different strate-gies influenced performance. The results demonstrate a spatial Dunning-Kruger effect; both men and women consistentlyoverestimated their performance. Womens estimates were lower than mens estimates were. Importantly, training influ-enced men and womens predictions of their performance in opposite directions; training increased mens confidence (butnot their performance), whereas training decreased womens confidence (but not their performance). The results suggestthat expectations and beliefs about spatial performance need to be considered when explaining training effects and sexdifferences