just a thought, but one of the biggest evolutionary points of emotions, which are just instincts label by self aware man, is to filter our experiences into good pile and bad pile. then experiences and thoughts are re-integrated into the brain with the new emotional weighting. This happens in order to make us strive for more rewards(dopamine). so maybe hals dreams can be emotionally weighted so when they are re-integrated, he only keeps the good data. good as in coherent,but also good as in positive experiences....just a thought or am i crazy?