Nightmare frequency is related to a propensity for mirror behaviors
Introduction
Mirror behaviors, such as empathizing with another’s emotions or imitating their actions or speech, are more frequent among individuals who act out fictive behaviors in their dreams than they are among individuals who do not (Nielsen & Kuiken, 2013). Dream-enacting behaviors are frequently the culmination of highly disturbing dreams, including the typical nightmares of college students (Nielsen, Svob, & Kuiken, 2009), the unpleasant ‘baby-in-peril’ dreams of postpartum mothers (Nielsen & Paquette, 2007), and the violence-filled nightmares of patients with REM sleep behavior disorder (RBD) (Schenck et al., 1986, Schenck et al., 2009). However, it is unknown whether a propensity for mirroring others’ emotions and behaviors while awake is associated specifically with self-reported nightmare frequency.
The possibility of an association between mirror behaviors and disturbing dreams is pertinent both for clarification of nightmares as a clinical problem and for a coherent theory of nightmares. Clinically, nightmares are associated with several pathologies (see Levin & Nielsen, 2007 for review) whose relationship to mirror behaviors and the mirror neuron system is under investigation. For example, nightmares are symptomatic of affective disorders, such as bipolar disorder (Beauchemin and Hays, 1996, Mehl et al., 2006) and alexithymia, both of which are linked to anomalies in the mirror neuron system (Kim et al., 2009, Moriguchi et al., 2009). Similarly, nightmares are predictive of suicidal and self-harm behaviors (Li et al., 2010, Nadorff et al., 2011, Sjostrom et al., 2009), which may be linked to mirror processes to the extent that they are influenced by similar behaviors in others, e.g., contagious suicides (Hagihara and Abe, 2012, Jeong et al., 2012, Yang et al., 2013). Nightmares also commonly accompany dissociative disorders (e.g., Watson, 2001), the symptoms of which can be influenced by observational learning, including media portrayals of the disorder (e.g., Lilienfeld et al., 1999).
A related question concerns the types of mirror behaviors that might be associated with nightmares. Factor analysis of the Mirror Behavior Questionnaire (MBQ) revealed four types of mirror behaviors (Nielsen & Kuiken, 2013): Empathy/Emotional Contagion, Behavioral Imitation, Sleepiness/Anger Contagion, and Motor Skill Imitation. This pattern is broadly consistent with other research that supports a distinction between cognitive and emotional empathy (Reniers, Corcoran, Drake, Shryane, & Vollm, 2011), the multidimensionality of empathy (Derntl et al., 2010), and the existence of different forms of motor resonance (Gazzola, ziz-Zadeh, & Keysers, 2006) and emotional contagion (Lundqvist, 2006). There is also a substantial literature on sex differences in (1) empathy, with females being more empathic; (2) contagious behaviors, with females exhibiting more emotion-congruent facial responses and higher self-reported contagion (Sonnby-Borgstrom et al., 2008, Wakabayashi et al., 2012): and (3) the early developmental origins of emotional contagion (Geangu, Benga, Stahl, & Striano, 2010). Both sex and age are important factors in the etiology of nightmares as well.
The goal of the present study was therefore to assess possible relationships between nightmares and mirror behaviors in a college student population. The MBQ (Nielsen & Kuiken, 2013) permitted us to examine the specific types of mirror behaviors that might characterize subjects who frequently report nightmares.
Section snippets
Methods
Subjects were 480 students enrolled in a first-year university psychology course who received partial course credit for participation. Of these, 188 were male (19.2 ± 1.73 years; range: 17–27) and 292 were female (19.0 ± 1.55 years; range: 17–29). They gave informed consent and participated voluntarily; they were also free to choose an alternative educational activity for course credit. The male and female groups did not differ in age (p = .18).
All subjects completed an extensive battery of
Nightmare frequency (NMF)
Mean NMF for the entire sample was 0.72 ± 1.02 (range: 0–6; median: 0) or the recall of slightly less than 1 nightmare in the last 30 days. Distributions of recall by group (Lo-NMF, Med-NMF, Hi-NMF) and sex are shown in Table 1. Females reported a higher NMF (.84 ± 1.09) than did males (.53±.87; Mann–Whitney U = 3.40, p = .001).
MBQ total score
Mean MBQ score was 1.51 ± 0.39 with a median of 1.5, mode of 1.38, and range of 0.44–2.50 (out of 3.00). The distribution of scores was relatively normal (Fig. 1, left panel). A 3 ×
Discussion
These results provide preliminary evidence that nightmare frequency is associated with a tendency to express waking mirror behaviors. They support the notion that a previously observed association between mirror behaviors and dream-enacting behaviors (Nielsen & Kuiken, 2013) reflects a mirror neuron mechanism that underlies both waking mirror behaviors and nightmares. Nightmares may not be the only source of dream-enacting behaviors, but they appear to be a notable one.
The precise mechanisms
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