Are psychedelic states induced by drugs such as LSD or magic mushrooms really higher states of consciousness? What do they tell us about leading theories of consciousness? An ambitious paper by Tim Bayne and Olivia Carter sets out to give the answers.

You might well think there is an insuperable difficulty here just in defining what ‘high’ means. The human love of spatial metaphors means that height has been pressed into service several times in relevant ways. There’s being in high spirits (because cheerful people are sort of bouncy while miserable ones are droopy and lie down a lot?). To have one’s mind on higher things is to detach from the kind of concerns that directly relate to survival (because instead of looking for edible roots or the tracks of an edible animal, we’re looking up doing astronomy?). Higher things particularly include spiritual matters (because Heaven is literally up there?).  In philosophy of mind we also have higher order theories, which would make consciousness a matter of thoughts about thoughts, or something like that. Quite why meta-thoughts are higher than ordinary ones eludes me. I think of it as diagrammatic, a sort of table with one line for first order, another above for second, and so on. I can’t really say why the second order shouldn’t come after and hence below the first; perhaps it has to do with the same thinking that has larger values above smaller ones on a graph, though there we’re doubly metaphoric, because on a flat piece of paper the larger graph values are not literally higher, just further away from me (on a screen, now… but enough).

Bayne and Carter in passing suggest that ‘the state associated with mild sedation is intuitively lower than the state associated with ordinary waking awareness’. I have to say that I don’t share that intuition; sedation seems to me less engaged and less clear than wakefulness but not lower. The etymology of the word suggests that sedated people are slower, or if we push further, more likely to be sitting down – aha, so that’s it! But Bayne and Carter’s main argument, which I think is well supported by the evidence, is that no single dimension can capture the many ways in which conscious states can vary. They try to uphold a distinction between states and contents, which is broadly useful, though I’m not sure it’s completely watertight. It may be difficult to draw a clean distinction, for example, between a mind in a spiritual state and one which contains thoughts of spiritual things.

Bayne and Carter are not silly enough to get lost in the philosophical forest, however, and turn to the interesting and better defined question of whether people in psychedelic states can perceive or understand things that others cannot. They look at LSD and psilocybin and review two kinds of research, questionnaire based and actual performance test. This allows them to contrast what people thought drugs did for their abilities with what the drugs actually did.

So, for example, people in psychedelic states had a more vivid experience of colours and felt they were perceiving more, but were not actually able to discriminate better in practice. That doesn’t necessarily mean they were wrong, exactly; perhaps they could simply have been having a more detailed phenomenal experience without more objective content; better qualia without better data/output control. Could we, in fact, take the contrast between experience and performance as an unusually hard piece of evidence for the existence of qualia? The snag might be that subjects ought not to be able even to report the enhanced experience, but still it seems suggestive, especially about the meta-problem of why people may think qualia are real. To complicate the picture, it seems there is relatively good support for the idea that psychedelics may increase the rate of data uptake, as shown by such measures as rates of saccadic eye movements (the involuntary instant shifts that happen when your eyes snap to something interesting like a flash of light automatically).

Generally psychedelics would seem to impair cognitive function, though certain kinds of working memory are spared; in particular (unsurprisingly) they reduce the ability to concentrate or focus. People feel that their creative capacities are enhanced by psychedelics; however, while they do seem to improve the ability to come up with new ideas they also diminish the ability to tell the difference between good ideas and bad, which is also an important part of successful creativity.

One interesting area is that psychedelics facilitate an experience of unity, with time stopping or being replaced by a sense of eternity, while physical boundaries disappear and are overtaken by a sense of cosmic unity. Unfortunately there is no scientific test to establish whether these are perceptions of a deeper truth or vague delusions, though we know people attach significance and value to these experiences.

In a final section Bayne and Carter take their main conclusion – that consciousness is multidimensional – and draw some possibly controversial conclusions. First, they note that that the use of psychedelics has been advocated as a treatment for certain disorders of consciousness. They think their findings run contrary to this idea, because it cannot be taken for granted that the states induced by the drugs are higher in any simple sense. The conclusion is perhaps too sweeping; I should say instead that the therapeutic use of psychedelic drugs needs to be supported by a robust case which doesn’t rest on any simple sense of higher or lower states.

Bayne and Carter also think their conclusion suggests consciousness is too complex and variable for global workspace theories to be correct. These theories broadly say that consciousness provides a place where different sensory inputs and mental contents can interact to produce coherent direction, but simply being available or not available to influence cognition seems not to capture the polyvalence of consciousness, in Bayne and Carter’s view.

They also think that multidimensionality goes against the Integrated Information Theory (IIT). IIT gives a single value for level of consciousness, and so is evidently a single dimension theory. One way to achieve a reconciliation might be to accept multidimensionality and say that IIT defines only one of those dimensions, albeit an important one (“awareness”?). That might involve reducing IIT’s claims in a way its proponents would be unwilling to do, however.