The aim of this experiment was to investigate the temporal reference of elements which served as the mnemonic basis for dreams. Free associations with REM and Sleep Onset dreams were collected to determine the quality of the memories presumably activated during the producrion of the two types of dream. Associations referring to particular episodes of the dream- er's life were classified, according to their temporal dating, into Day residues, Recent residues, Remote residues. The hypothesis that there are differences in the temporal reference of the mnemonic sources of REM and sleep onset dreams has been confirmed. Day residues are significantly more associated with sleep onset than REM dreams. Moreover, in sleep onset, Day residues are significantly more frequent than Remote residues, while this is not true for REM dreams. Day residues are more easily available to sleep onset than REM dreaming because of the recent encoding which characterizes this kind of memory traces. In both sleep phases recent residues are more frequently used in constructing the dream.
