There are, of course, countless theories of dreaming. Some have explicitly considered the role of social interactions in dreams, while others make more general statements about dream content. One of the latter is the Continuity Hypothesis (CH), which states that dreams reflect waking life experiences (Schredl & Hofmann 2003) or, more specifically, that our waking concerns, thoughts, and experiences have a causal influence on subsequent dream content. Thus, if certain types of social contacts or interactions become more frequent (or less frequent) in waking life, their simulation in dreams becomes correspondingly more (or less) frequent.
This general principle seems to hold in many cases. For example, in hunter-gatherer societies, where people perceive and interact with wild animals on a daily basis, the proportion of animal characters remains high (as it is in children’s dreams across cultures), whereas in highly industrialized societies, the animal percentage decreases dramatically from childhood to adulthood. But the CH merely restates this empirical relationship; it cannot answer the theoretical question of why in young children’s dreams the proportion of animal characters is high to begin with. TST (Revonsuo 2000) has attempted to answer this question by referring not to personal experiences in waking life, but to a universal bias that is built into the default values of dream content during human evolutionary history.
The CH, even if on the right track in many cases, is too vague and general as a theoretical explanation of the details of dream content. It does not predict in any detail how and why the causal relationship between waking and dreaming works. It also does not specify in any detail what counts as a “continuity” and what would count as a “discontinuity” between waking life experiences and dream simulations of the same. If something happens in waking life how closely similar will the dream simulation be to its waking origin, when will the same (or a similar) content appear in dreams, how frequently and for how long will it be incorporated into dreams, and so on? These questions have been studied under the concepts of day residue (Freud 1950) and the dream lag effect (Nielsen & Powell 1989). The CH takes almost any similarity between waking life and dream life as a confirmation of the continuity hypothesis. But “similarity” as a relationship between two phenomena is undefined, ambiguous, and vague. Something that in one respect is similar to its waking counterpart is in another respect dissimilar from it; thus it can be interpreted as either continuous or as discontinuous with waking life. Obviously, if the very same evidence could be counted as either supporting or disconfirming a theory, there is something wrong with how the theory is formulated.[2]
As long as the CH remains vaguely formulated, almost anything can be counted as its support. If the hypothesis does not specify in any detail the potential empirical observations after which its predictions would be falsified, it is not an empirically testable theory. Unless it is formulated in a much more specific manner, so that risky, exact predictions can be derived from it, its explanatory power remains correspondingly weak. In one study where more precise predictions from CH were derived, the CH was found not to be valid as a general rule concerning how often different everyday activities are reflected in dreams (Schredl & Hofmann 2003).
Perhaps a more precise prediction that could be derived from CH can be formulated in the following way: according to CH, dreams represent a random sample of recent waking experiences (or a random sample of their memory representations). The quantities of different types of contents in dreams will therefore passively reflect the proportion of their occurrence in waking life in the recent past (or the memory representations of waking life). If CH is formulated in this manner, as a prediction of random sampling and passive mirroring of recent waking life, then any systematic deviation from a random sample of waking contents (or memories thereof) would count as evidence against the CH. A deviation from passive mirroring of waking life would suggest that some kind of selective mechanism is at work. An active selection bias of particular contents to be either included in dreams or to be left out would be expected to result in a disproportionately exaggerated or diminished frequency of that content in dreams as compared with waking life. This kind of formulation of the predictions of CH makes it a testable theory.
Some more specific suggestions about dreaming as social simulation have been put forward in the literature. Brereton’s (2000) Social Mapping Hypothesis suggests that dreaming simulates, among other things, the awareness of other persons (social perception) and their internal mental states (mentalizing or theory of mind-abilities). This theory proceeds from an evolutionary standpoint, and considers dreaming as a rehearsal ground for emotional and perceptual abilities related to the mapping of the body image of the self into an emotionally-salient social space. Others have also hypothesized that our mindreading abilities could potentially be a target of simulated social perception in dreams (Kahn & Hobson 2005; McNamara et al. 2007). Moreover, Nielsen & Germain (2000) have suggested that dreaming might simulate attachment relationships and interpersonal bonds in ways that would maintain their adaptive significance even today, and Humphrey (2000) has compared the social functions of dreaming to those of play. The possibility that dreaming simulates pro-social and aggressive social interactions in distinct sleep stages, and that these simulations might exert a regulatory influence on our waking social lives, was put forward by McNamara et al. (2005). Last, Franklin & Zyphur (2005) have considered how the simulation function of dreams might be expanded to cover social cognition and complex socio-cultural situations.[3]
The problem with the above social simulation theories of dreaming is that either they are not detailed enough to be testable, or that few, if any, have ever been directly tested against competing theories. They are interesting general ideas, but not strictly formulated theories that could be directly tested, or from which detailed predictions and potential explanations for the social contents of dreaming could be derived. Thus, these theoretical ideas have not led to a strong empirical, hypothesis-driven research program that would be able to systematically test the plausibility of these theories.
Whenever we formulate theories of dreaming, or of the functions of dreaming, they should be formulated in such detail that empirically testable predictions can be derived from them. Statements that are too vague or too general (e.g., “dreams are continuous with waking life”; “dreams are social simulations”) are difficult to test as such. The predictions derived from general statements are too unspecific. Thus, the theories remain uninformative but of course consistent with almost anything we might realistically expect to find in dream content. If a theory makes no detailed, risky predictions about what should or should not be found in dream content (under some specific circumstances or in specific populations) it doesn’t have much explanatory power, either. So far there is no detailed, convincing, testable theory of the nature and the function(s) of social simulations during dreaming. There is also a lack of data on the detailed quantity and quality of simulated social interactions in dreams, and how they relate to real social interactions in the waking life of the same person. In the rest of this paper, we will try to outline ideas for the theoretical basis of a social simulation theory of dreaming and to formulate some empirically-testable hypotheses directly derived from the theory.