Dream emotions: a comparison of home dream reports with laboratory early and late REM dream reports
One methodological discrepancy between studies lies in the experimental setting of the study; specifically, whether dream reports are collected at home or in the sleep laboratory. It has been debated whether and to what extent the (emotional) content of dream reports collected in the two settings is comparable (Domhoff, 2005; Schredl, 2008; Waterman et al., 1993). However, only a few studies have compared the emotional content of dream reports obtained from the same individuals in the two settings (see Table 1 for a summary of the key characteristics and findings).
As evidenced in Table 1, when dream reports are obtained using constant sampling (morning awakenings in both settings) and reporting (either written or oral in both settings) conditions, no differences between laboratory and home dream reports are found, at least when rated by external judges (Foulkes, 1979, study 3; Weisz and Foulkes, 1970). However, when non‐constant sampling [home morning awakenings versus laboratory serial rapid eye movement (REM) awakenings] and reporting (written home dream reports versus verbal laboratory dream reports) conditions are used, home dream reports contain more emotions, especially negative emotions (Foulkes, 1979, study 4; Okuma et al., 1975; St‐Onge et al., 2005). These differences may arise because, at home, dream reports derive from either REM or non‐REM (NREM) sleep, whereas in the laboratory they derive from REM sleep. However, it has been shown that the emotional content of dream reports obtained upon morning awakenings from REM and NREM sleep is similar (Cicogna et al., 1998; McNamara et al., 2007). Thus, the differences seem to occur mainly because dream reports derive from different times of night: home dream reports from late REM or NREM sleep dreams and laboratory dream reports from both early and late REM sleep dreams. Indeed, late REM sleep dream reports, compared to early REM sleep dream reports, have been found to have greater emotionality or emotional intensity (Sikka et al., 2014; Wamsley et al., 2007; cf. Fosse et al., 2001). However, no studies have compared home dream reports collected from morning awakenings directly with laboratory dream reports collected separately from early and late REM sleep periods. Therefore, the aim of this study was to compare the emotional content of dream reports collected at home upon morning awakenings with those collected in the laboratory upon early and late REM sleep awakenings.