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Can we learn language while asleep?

[By Humphrey M Kapau]

There is a raging academic battle of facts and myths surrounding ‘hypnopaedia’ (that is, learning while asleep).

It is a battle as fierce as the 1820 Battle of Mhlatuze River between the Zulu and Ndwandwe tribes after the first Zulu civil war of 1817 to 1819. The only difference is that the battle on hypnopaedia is a battle of thoughts among scholars such as neurolinguists, psychologists and philosophers.

To start with, most studies on hypnopaedia have been accused of being overzealous, ambitious and untraditional in the manner they handle reality and knowledge of research pillars (i.e. ontological and epistemological aspects of research). Such studies have been likened to someone trying to witness a snake drinking water, something that only a Lozi man can do and not the so-called Tonga or Kaonde man. What do neurolinguists know so far about sleep-learning and language? This article presents debate highlights and established knowledge on one of the most elusive and fascinating topics in neurolinguistic research.

What is hypnopaedia?

Sleep-learning, as hypnopaedia is sometimes called, comes from two Greek words, notably, ‘hypno-’ and ‘paedia/pedia’. In Greek, ‘hypno-’ means ‘sleep’; while ‘-paedia/pedia’ can mean either ‘education’, ‘learning’ or ‘children’ depending on context (e.g. ‘encyclopaedia/ encyclopedia’ means ‘all-round/complete learning’ while ‘paediatrics/pediatrics’ relates to medical branch dealing with children). In the case of hypnopaedia (also spelt as ‘hypnopedia’), the two words that make it are translated to mean ‘sleep-learning’ and refers to learning while asleep by way of listening to recordings or to someone speaking (Klein,1971; Schlegel,2021).

Hypnopaedia drew the attention of scientists in dramatic fashion. It first started as a fictional word, coined by Aldous Huxley in 1931, in his novel ‘Brave New World’. In the novel, one of the characters by the name of Reuben Rabinovitch, a Polish, hears a radio broadcast transmitted in English in his sleep and recites it when he wakes up. His success with hypnopaedia even makes government officials begin using it to inculcate morals in citizens during sleep.

“This fictional idea spawned actual research on hypnopaedia in the 1950s, and many studies were done to verify whether sleep-learning was possible” (Klein,1971:4). Arising from the actual research on sleep-learning, scholars have over the years been divided over the authenticity of hypnopaedia. One group argues that it is possible to learn in sleep if someone played an audio or spoke to the sleeping person (e.g. LeShan,1942; Fox and Robbins,1952).

In contrast, the anti-hypnopaedia camp maintains that no form of learning can take place when we are asleep because learning is an active, conscious process that demands our brains to be awake (e.g. Emmons and Simon,1960). They accuse pro-hypnopaedia scholars of using faulty techniques and methods in their research. In their defense, pro-hypnopaedia scholars have pointed to the positive outcomes of their various experiments, among them “the works of Hoskovec in 1966 and Rubin in 1968 and 1971 whose findings suggested that people were capable of learning during sleep, though the learning was of simpler nature” (Klein,1971:5).

Despite the debate, newer evidence is indicating that hypnopaedia is not entirely imaginary (Schlegel, 2021). Before we look at this new knowledge, we first need to understand what ‘sleep’ really is.

Parts and phases of sleep

No discussion on hypnopaedia can be understood and appreciated without first understanding the science of sleep. Sleep is part of humans’ biological clock (i.e. a 24-hour clock known as the circadian rhythm) and is activated in the night by a hormone called melatonin so that we fall asleep, and suppressed during the day so that we remain awake (Silver,2020). Our entire sleep is divided into two major parts, namely, non-rapid eye movement sleep (i.e. non-REM sleep or NREMS) and rapid eye movement sleep (i.e. REM sleep or REMS).

Every time we fall asleep, we begin with non-REM sleep which consists of four stages. Stage 1 sleep takes about 75-80 per cent of our sleep during which our muscles become more relaxed and consciousness decreases. In Stage 2 sleep, consciousness and awareness continues to decrease and by Stage 3 (also called the ‘slow wave sleep’ – SWS or ‘deep sleep’), our consciousness and awareness prevalent in Stages 1 and 2 of sleep would have almost ceased to exist, thereby making Stage 3 sleep a transition point to Stage 4 sleep. The moment we enter Stage 4 sleep (also called Delta sleep stage, or loosely speaking, ‘deeper sleep’), we would have lost all consciousness and awareness. That is when we would switch from non-REM sleep to rapid eye movement (REM) sleep where dreaming is now possible.

Though REM sleep is characterised by eye movement at 30 degrees horizontally/vertically, we can’t see because no signal is sent to the brain (Klein,1971; Hamzelou,2015). The parts and phases of sleep repeat many times during the course of our sleep as we alternate between unconscious/unawareness sleep (Stage 4 and REM sleep) and semi-conscious/semi-awareness sleep (Stage 1–3 sleep). We are described as ‘awake’ when we are fully conscious (Leavitt,2019).

Established knowledge on hypnopaedia and language

Although learning in sleep is still deemed impossible until proven otherwise by satisfactory evidence, scholars now know the following about hypnopaedia. Firstly, it is possible to help a sleeping person revise particular language content when their sleep level is at Stages 1, 2 or 3 (the semi-conscious/semi-awareness sleep stages). Revision is possible at the aforesaid stages because it has to do with information previously acquired while awake which is now administered to a half-asleep brain, unlike learning which involves dealing with new information whose absorption demands a conscious mind (i.e. being awake). However, when one’s sleep level enters either the Delta stage (i.e. the unconscious/unaware stage of sleep) or the rapid eye movement (REM) sleep phase (i.e. dreaming phase), it is no longer possible to revise because consciousness and awareness would have entirely disappeared to give way to a type of sleep where information consciously learnt and semi-consciously revised is consolidated in the long term memory (Walker,2005; Clark,2016; Anzenhofer and Moynihan,2021).

Secondly, due to varying complexity of topics in language, not every language topic can be revised in Stages 1, 2 or 3 sleep (Clark,2016). This is logical in that some things we learn demand a conscious brain even when revising them. For example, it would be practically impossible to help someone revise language topics like generative grammar, minimalist programme and semiotic assemblages in their sleep because such topics demand a sound and healthy brain to understand. However, simple word lists (e.g. ball, phone) and onomatopoeic words (i.e. words which imitate the natural sound of things they represent e.g. ‘moooo’ for the sound of cow; ‘click’ for the sound a camera makes; and ‘hiss’ for snake sound) can be revised using hypnopaedia. Some scholars think onomatopoeic words are not only revisable but also learnable in sleep but available scientific evidence says otherwise (Schlegel,2021).

Lastly, although nothing can substitute active learning, being exposed to a word or phrase in sleep is now known to help with language consolidation in our brains – “but only if the person has already been learning this word or phrase while awake” (Mosalingua,2016). Using what is known as Targeted Memory Reactivation (TMR) technique in which words are said or availed in audio format to a person whose sleep is especially at Stage 3 (i.e. slow-wave sleep or SWS), neurolinguists have established that language information can be spontaneously replayed and analysed by our brains at that stage before it is committed to our long term memory through a process called consolidation (Walker,2005).

The findings involving Targeted Memory Reactivation (TMR) technique in hypnopaedia have equally confirmed that: people who sleep before and after studying tend to perform better than those who deprive themselves of sleep; people who are exposed to TMR technique in hypnopaedia tend to remember more items than participants who are left to sleep; and that sleep deprivation can negatively affect our memory retention. These findings confirm the findings in psychology about the relevance of sleep in information consolidation especially during slow-wave/Stage 3 sleep (e.g. the Active System Consolidation Hypothesis – Rasch and Born,2013; Sobczak,2017).

So…can we learn a language while asleep? It is still deemed impossible until proven otherwise because learning is a complex thing that demands a conscious brain. What is known is that we can use sleep to revise simple language topics previously acquired when we were awake. Even then, such revisions can only happen at particular stages of sleep where we are not fully asleep.

Next week, I will take you to forensic linguistics where I will look at facts about handwriting that crime investigators focus on when examining a hand-written note left behind by a crime suspect. Nicklaus Kruger…thanks for rallying international support for this column.

The author is a systemic functional linguist and Special Research Fellow (PhD) at the University of the Western Cape, South Africa. His other research fields include neurolinguistics, forensic linguistics, psycholinguistics, semiotics, corpus linguistics, cognitive linguistics, African languages and literature. He has also taught language at UNZA. Contact: hmksettings@rocketmail.com, WhatsApp: +260 956 315380.

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