What is reality discrimination?

In everyday life, we discriminate ‘real’ from ‘imagined’ all the time without noticing the skill involved. That is, we distinguish our own thoughts from what we assume to be a public reality independent of those thoughts – a skill called reality monitoring or reality discrimination. Experiments in which people are asked to see or hear some stimuli, and to imagine others, show that many different features can be used for the purpose of discrimination, including how stable, detailed, or vivid the experiences are, and whether they can be voluntarily controlled. One study presented participants with either complete or incomplete well-known word pairs and tested how well they remembered which words were actually presented and which needed completing imaginatively: visual presentation resulted in better reality monitoring than auditory presentation, and speaking the words out loud worked better than internally verbalising (‘thinking’ about) them.

Distinguishing memories of events that really happened from events we have only imagined is particularly difficult, and its failure results in false memories – that is, convincing ‘memories’ of events that never actually happened. These can be created when we tell the same story many times, with slight variations, and then remember the last version we told. The latest version retroactively interferes with the original memory. False memories can also be created when a family story keeps being told or a photograph from childhood convinces you that you can remember that day on the beach. And they can have lasting effects on behaviour.

It is super important to make the distinction between real and imagined. False memories are most problematic when people ‘remember’ sexual abuse that never happened or identify suspects they never saw. There have been tragic cases in which therapists allegedly recovered repressed memories of sexual abuse under hypnosis and convinced their patients that the events really happened when they did not.

Real memories tend to be more detailed and more easily brought to mind than false memories. Sometimes real memories can be identified because we can put them in context with other events or remember when and how they happened – a skill called source monitoring. This is not important for learning skills and facts. For example, you may reliably and correctly remember the speed of light, the capital of Germany, and the name of the man next door, without needing to remember when or where you learned them, but for autobiographical memory the context is important. If the memory of an event in your life is detailed and plausible, and fits with other events in time and place, then you are more likely to judge that it really happened. We probably all hold false memories, and even our valid memories may consist of accurate elements mixed with plausible concoctions and embellished with invented details. This is because autobiographical memory is not a cupboard where you can open doors to access all the facts. Rather, remembering is a process of active reconstruction shaped as much by our current goals and priorities as by the realities of the past.

The dividing line between real and unreal is obviously blurred in the context of memory. The division is particularly interesting when it concerns experiences for which there can be no public corroboration, including dreams, fantasies, and hallucinations.

How do we define hallucinations?

The term ‘hallucination’ is not easy to define (obviously), although we can make some sort of rough description. Hallucinations were distinguished from illusions early in the nineteenth century, on the basis that hallucinations are entirely ‘internal’ whereas illusions are misperceptions of ‘external’ things. By contrast, hallucinations are perceptual experiences not elicited by an external stimulus. This distinction is still used but there is no clean dividing line. For example, imagine that someone sees the ghost of a headless monk float across the altar in church. We might say that there was nothing there and that the monk was a hallucination, or alternatively that a faint swirl of candle smoke or incense was mis-perceived and that the monk was an illusion. So it can happen the argument for both terms can be made.

True hallucinations are sometimes distinguished from pseudo-hallucinations, in which the person knows that what is seen or heard is not real, whereas in true hallucination, people in the moment do believe they are experiencing reality, even when they are not. One problem with this distinction is that if taken too literally there must be very few true hallucinations. Even with a double dose of LSD, most people still know that the arms of the enormous monster threatening to engulf them are really the branches of a tree.

Another distinction is between hallucinations and mental imagery. Hallucinations are sometimes distinguished from imagery by their resemblance to publicly shared perceptions rather than private thoughts, or by their uncontrollability. If we voluntarily imagine a tropical beach with the sound of waves lapping on the sand, this is usually called imagery, but if the vision forces itself on our mind and won’t go away it would be called a hallucination.

Prevalence

Here, the book blabbers a lot about the history of ghost illusions and such, which is interesting and all, but unimportant. The important thing is that a recent cross-cultural estimate of hallucination based on surveys from eighteen countries found that 5.2% of respondents had experienced a hallucination in their lifetime (compared to only 1.3% reporting delusional experiences involving paranoid beliefs about mind control, being followed, etc.), with lower instances in low-income countries and amongst men. All this suggests that the tendency to hallucinate varies along a continuum, with pathological cases at one end, people who never hallucinate at the other, and most of us in between.

Context

As you well know, hallucinations are related to mental illnesses such as schizophrenia and bipolar disorder. Other common causes of hallucinations are drugs, physical illness, starvation, and sleep deprivation, as well as ritual practices such as rhythmic drumming, whirling, dancing, chanting, flagellation, or control of the breath. Sensory deprivation is a powerful way to induce hallucinations. It is as though when deprived of input, our sensory systems find patterns in what little information they have, lower their criteria for what to accept as real, or turn to internally generated stimulation instead. This is simply an intensified version of the universal human habit of pareidolia: seeing familiar patterns on the flimsiest pretext, like turning lunar contours into the man in the moon or hearing messages in music played backwards..

Also common are hallucinations that are combined with the perceived world, as happens to lone explorers and climbers who see or hear imagined companions, and to people who become blind through either retinal or brain damage.

Theories of consciousness

In essence, the problem is the same: how can physical processes in the brain give rise to subjective experience? Yet perhaps the familiarity of thinking about perceiving the ‘real’ world blinds us to the seriousness of the problem, which may seem more obvious when thinking about hallucinations. We know (at least roughly) what sort of cortical activity causes someone to have a potent hallucination of a bright golden tunnel, for instance. But how can the experience of a golden tunnel be caused by, or simply be, that neural activity?

For some theories of consciousness, hallucinations provide a special stumbling block. For example, sensorimotor theories entail no pictorial images or representations inside the head; instead, perceiving means having mastery of the sensorimotor contingencies between sensory input and motor responses such as moving your head, blinking, or running your fingers over something to change the input. Other theories use hallucinations in support. Higher-order theories take them as evidence that one can have a second-order thought (i.e. one can represent to oneself) that one is in a state when this is not true.

Dennett (AGAIN) proposes what would now be called a predictive-processing account, based on ‘generate-and-test’ theories of perception: perceptual hypotheses based on expectations and interests are constantly created and either confirmed or disconfirmed by the sensory input. This cyclical process of generate-and-test produces a model of the world that is constantly being updated but relies on having sufficient sensory input. When deprived of meaningful input, the data-driven part of the hypothesis-generating system lowers its threshold for noise. This means the answers coming back from the testing-and-confirmation part make little sense, and it goes into a random cycle of confirmation and disconfirmation. The result is hallucinations based on things that the system already knows about, whether that is the simplest of geometric designs or highly detailed hallucinations produced by anxious expectation followed by chance confirmation.

Conclusion

So is the hallucinated tunnel ‘real’? In one sense, it is not real because there is no physically detectable tunnel present, and other people in the vicinity would not see any tunnel. In another sense, it is real because there is physically measurable activity in the person’s brain. We might also say it is real because it has measurable later effects on the person’s behaviour. This is true whether you are seeing an actual tunnel as a tunnel (vision), seeing a set of concentric circles as a tunnel (illusion), or seeing nothing-in-particular as a tunnel (imagining or hallucinating).

What is extra-sensory perception?

Even if hallucinations on the strictest definition (not knowing you are hallucinating) are relatively rare, there is no doubt that hallucinations exist: their existence is the experience. Other phenomena on the borders of the imagination make stronger claims for the nature of their reality – for example, that what looks like ‘mere imagining’ may be a form of mental travel or communication at a distance. And this takes us into the realm of parapsychology.

Parapsychology is the study of alleged psychic phenomena and other paranormal claims, such a telepathy. And for those who consider it real, psychic phenomena are popularly thought to be evidence for the ‘power of consciousness’, due to ‘consciousness interactions’ or ‘consciousness-related anomalies’. The book thus also defines parapsychology as ‘the scientific study of interactions between living organisms and their external environment that seem to transcend the known physical laws of nature. Parapsychology is a component of the broader study of consciousness and the mind’.

J.B. Rhine started the trend and came with the term ESP, aka Extra-Sensory Perception. The least outlandish version of this ESP is feeling that someone is looking at your back or sensing someone being about to ask a question.

How about conjuring up other worlds?

All of us conjured other worlds when playing as children: inventing food and drinks for dollies’ tea-time, imagining illnesses to be cured by ‘doctors and nurses’, and creating invisible cargoes to be carried by toy trucks on imaginary roads. Many children, especially only children, have imaginary playmates. Some children play and talk with the same friend for many years, though not often past the age of ten. In the early years, the playmates are described as solid and real, but older children rarely see them that way. Most imaginary companions are people, usually of the same sex as the child, but they can be animals, invisible toys, storybook characters, and even things like clouds or doorknobs .

This capacity for creating other characters and other worlds continues into adulthood in daydream fantasies and in the enjoyment of fiction- and poetry-reading, film-viewing and theatre-going, electronic gaming, creative writing, painting, and other arts, which have been described as ‘qualia machines’ offering up new varieties of consciousness. When we feel ‘immersed’ or ‘absorbed’ in a world created by a written text or a set of moving images, we may retain more or less awareness of the environment in which we are reading or watching. This might depend on many other factors, including our evaluations of or empathy with the protagonists, the richness of our mental imagery, our familiarity with the story’s genre, and maybe even basic demographic factors like gender.

Many native tribes and ancient cultures also have practises and rituals where they guide their people and such a different world, different consciousness. Experienced ayahuasca users travel in this world or other worlds, according to their traditions, and describe non-ordinary ways of seeing. They claim that the gods, demons, heavens, and hells that they visit are as real as, or even more real than, the ordinary world of normal vision. They describe gaining spiritual insights and a deeper understanding of reality and of themselves.

So is it real?

Some kind of distinction is needed, otherwise we would not be able to make judgements about the reliability of eyewitness evidence after a crime, or reassure someone who hallucinates a threatening figure that they need not be afraid. But when we say things like ‘it’s all in the mind’ to mean that the realm of the imagination, or of the mind more generally, is unreal, we go too far, because body, mind, and environment are always linked. Going too far has wide-ranging and serious consequences, from denying that mental illness is really real, to dismissing a whole spectrum of forms of consciousness as irrelevant to the investigation of ‘consciousness itself’ – whatever that is.

But then again, what is ‘real’? Obviously something happened to you, and the experience itself was real enough, wasn’t it?