Why did people across the world and throughout history believe that dreams can foretell what will occur in the future? In this paper, I attempt to answer this question within a cultural evolutionary framework by emphasizing the cognitive aspect of dream interpretation; namely, the fact that dreams were often viewed as meaningful and interpretable has to do with various psychological and social factors that influence how people obtain and process information regarding the validity of dream interpretation as a technique.
Through a comprehensive analysis of a large dataset of dream occurrences in the official Chinese historical records [and dream encyclopedias], I argue that the ubiquity and persistence of dream interpretation have a strong empirical component (predictively accurate dream cases), which is particularly vulnerable to transmission errors and biases. The overwhelmingly successful records of dream prediction in transmitted texts, I suggest, is largely due to the fabrication and retrospective inference of past dreams, as well as the under-reporting of predictive failures [selection bias, post hoc confirmation bias/publication bias]. These “positive data” then reinforce individuals’ confidence in the predictive power of dreams.
I finally show a potential decline of the popularity of dream interpretation in traditional China and offer a few suggestive explanations drawing on the unique characteristics of oneiromancy compared to other divination techniques.
[Keywords: cultural evolution, divination, oneiromancy, China, dream]
…Since this paper focuses on why people believe in the validity of oneiromancy, I propose to classify dreams by their epistemological status. Specifically, dreams as signs that usually need to be interpreted (often with professional expertise) and dreams as messages transmitted by other humans or human-like agents. This distinction is useful because it highlights how the perceived plausibility of the 2 kinds of dreams may be affected by one’s larger theoretical commitment.5 The famous Eastern Han skeptical thinker, Wang Chong (27–97 AD), for example, denies the possibility of message dreams but would entertain the possibility of certain sign dreams (2011).
…2.3. The cultural transmission of oneiromancy instructions and cases: Because of the indispensability of interpretation in sign dreams, there is often an interest and demand for instructions on how to correctly interpret of the content of dreams. In ancient China, there was a rich tradition in collecting and compiling dreams and their associated meanings (2017; 1989), and some of the most popular compilations, such as The Duke of Zhou’s Explanations of Dreams, can still be purchased in bookstores today (2013). As mentioned, the other aspect of cultural transmission of oneiromancy, the transmission of actual oneiromancy cases and the associated predictive outcomes (whether the prediction was successful or not), is also important; intuitively, one would not take dreams very seriously if all she hears about oneiromancy are failed predictions.
In China, oneiromancy cases were recorded in historical records, philosophical writings, and a wide range of literary forms (fiction, drama, poetry, etc.) (1989). During later dynasties, compilations of oneiromancy cases in the form of encyclopedias became popular with improved printing technology and the expansion of book publishing and distribution (2012, “Textualizing dreams in a Late Ming dream encyclopedia”). These encyclopedias often contained both dream prognostic instructions and actual cases; in an extensive analysis of a oneiromancy encyclopedia, Forest of Dreams compiled in 1636 CE, for example, 2012 shows that it contained not only instructions on how to interpret dreams but also many case descriptions of predictive dreams.
…In total, I collected 793 dream occurrences and recorded information regarding the type of dreams, the dreamer, the interpreter, the interpretation of the dream, and the predictive accuracy of the dream interpretation whenever possible (see Supplementary Material for details)…Figure 3 shows the relative proportion of dreams in terms of their predictive accuracy over historical time, and what is immediately obvious is that most dream occurrences are prophetic and have an associated confirmatory outcome. That is, whenever dreams are mentioned in these official historical records, the readers can expect that they are predictive of some later outcome, which is usually verified.
…To what extent were these stories believed? Historical texts do not offer straightforward answers, but we can, nonetheless, get some indirect clues. The famous skeptic during the Eastern Han dynasty, Wang Chong (27–97 AD) made the following comment on the story about how the mother of the first Han emperor Liu Ao dreamed of a dragon which presumably induced the pregnancy:
“From the chronicle of Gaozu (the later founding emperor of the Han dynasty) we learn that dame Liu (mother of Gaozu) was reposing on the banks of a large lake. In her dream she met with a spirit. At the time there was a tempest with thunder and lightning and a great darkness. Taigong (Gaozu’s father) went near, and perceived a dragon above her. She became enceinte and was delivered of Gaozu. These instances of the supernatural action of spirits are not only narrated, but also written down, and all the savants of the day swear by them.” (Lun Heng, Chapter 26 [?], 1907’s translation)
Thus, the story goes that Gaozu’s mother met with a spirit (and presumably had sexual intercourse with it) whose earthly manifestation was a dragon. According to Wang Chong, all the savants believed the veracity of the story, and he felt compelled to make a case against it. Of course, we do not know for sure whether the savants at the time genuinely believed in it or were merely pretending for political reasons. I suggest that some, perhaps many of them were genuine believers; even Wang Chong himself who argued against this kind of supernatural pregnancy believed that when great men are born, there will be signs occurring either in reality or dreams; he just does not believe that nonhuman species, such as dragons, can have sexual intercourse with humans.9
…To get a better sense of the number of such “political justification” dreams, I computed the percentage of such dreams11 out of the total number of dreams in different historical periods (Table 1).
From Table 1, we can clearly see that in all 3 historical periods (the reason for using Southern-Northern Dynasties as the dividing period will be made clear in §3.4), there is a nontrivial proportion of recorded dreams of such type. The percentage of dreams that could be used to justify political power is slightly higher in the pre-Southern-Northern Dynasties period and remains roughly constant in the later 2 periods.
In addition to intentional fabrication, some dreams may be “false memories”; that is, individuals may falsely remember and report dreams that they never experienced if these dreams were expected in the community. Recent psychological research on dreams has suggested that the encoding of memories of dreams may share the same neurocognitive basis as autobiographical memory and thus be subject to false memory (Beaulieu-2015). Psychologists have long known that subjective dream reports are often unreliable (2011, Perplexities of consciousness), and both theoretical accounts and empirical studies (Beaulieu-2015) have suggested that false memories may occur quite often in dreams (2013). In particular, 2013 points out there is often substantial memory loss in dream recall, which may lead to a “fill in the blanks” process.
While the dreamer may fabricate or falsely remember their dreams, the observer can also infer dreams retrospectively. Historians in ancient China often have an “if there is an outcome, then there must be a sign” mentality (2014) when recording events that were supposed be predicted by divination. Similarly, 2012 in her extensive treatment of dream interpretation of the Ming dynasty argues that written and transmitted dreams often reveal not what the dreamers actually dreamed of but what the recorder believed about the dreams. In my dataset, a substantial proportion of the dreams (11%) were described in a retrospective and explanatory manner, marked by the phrase “in the beginning” (chu). This way of writing gives the impression that the authors were trying to find signs that had already foretold the fate of individuals in order to create a coherent narrative.
Therefore, it is likely that the retelling and recording of dreams involved an imaginative and inferential process. 1999 points out that in early Chinese historical writing, authors may present cases where multiple individuals shared the same dream to prove its objective veracity. In my dataset, 1.3% of total dreams were reported to have multiple dreamers, and in the most extreme case, hundreds of people were said to have dreamed of the same thing.12 Although this is not statistically impossible, we can safely conclude (unless we seriously entertain the possibility of ghosts and spirits sending dream messages to multiple individuals simultaneously) that there was either some serious fabrication or false inference.
3.3. Under-reporting of failed dream predictions/wrong dream interpretations: In addition to the fabrication/retrospective inference of oneiromancy cases, under-reporting of failed predictions very likely existed to a substantial extent. The Song historian and philosopher Lü Zuqian (1137–1181 CE) made the following statement when commenting on the Confucian text Zuo Zhuan (~500 BC) regarding the accuracy of divination predictions:
“Some people ask: “Zuo’s record of crackmaking and milfoil divination cases were so amazing and spectacular; given such predictive accuracy, why are there so few [records] of them?” The answer: “from the Lord Yin [Duke Yin of Lu] till Lord Ai was a total of 222 years. Kings, lords, dukes, the literati and the commoner perhaps made tens of thousands of divinations, and only tens of the efficacious cases were recorded in Zuo’s book. These tens of the cases were collected in Zuo’s book and therefore feel like a lot; if they were dispersed into the 222 years it would feel extremely rare. If divination cases were of deceptive nature or had failed predictions, they would not have transmitted during their time and not be recorded in the book. I do not know how many tens of thousands of them were missed. If we had all of them [recorded], they would not be so rare.” (Donglai Zuoshi Boyi13)
The early Qing scholar Xiong Bolong (1616–531669355ya AD) commented on using dream signs to predict the sex of the fetus more specifically14:
It is not the case that all pregnant women have the same type of dreams, and it is not the case that if [she] dreams of certain signs she must give birth to son or daughter. There are also instances where one dreams of a bear15 yet gives birth to a daughter, and instances where one dreams of a snake and gives birth to a son. The poets [diviners] tell the cases where their predictions are fulfilled and not talk about the cases where their predictions failed. (Wuhe Ji16)
…my own fieldwork in southwest China among the Yi shows that many people are unwilling to reveal the divination or healing ritual failures of local shamans because these shamans are often friends and neighbors of the clients and there is the concern that spreading “accidental” failures may taint their reputation (Hong, submitted).
…As we have argued elsewhere, under-reporting of failed predictions may be a prevalent feature of divination in ancient societies (Anonymized, forthcoming). By selectively omitting failed predictions, these transmitted texts give a false impression that dream interpretations are overwhelmingly accurate, which, along with fabrication and ad hoc inference of predictive dreams, serves as a powerful mechanism to empirically sustain the validity of oneiromancy.
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