Research into the effects of sleep on memory has also shown differences in recall
due to the type of material to be remembered. Grieser et al. (23) found that REMdeprived
subjects recalled more "non-threatening" items than did non-REM-awakened
subjects, whereas non-REM-awakened subjects remembered more "threatening"
items than REM-deprived subjects. Tilley and Empson (24) found that the recall accuracy
of stories was significantly poorer when followed by REM deprivation than
when followed by stage-4 deprivation.