A hypnotist tells a subject that their outstretched arm will begin to rise upward as though tied to an invisible balloon. To their astonishment, the subject’s arm rises just as suggested, and seemingly without their intention. While it may appear as though the subject is being controlled by the hypnotist, it is well established that nobody can be hypnotised against their will. Hypnosis therefore seems to present a paradox; to respond to a hypnotic suggestion that your arm will move is to voluntarily perform an apparently involuntarily action. How can this hypnotic response be explained?
Over 30 years ago Benjamin Libet and colleagues conducted a series of classic experiments in which participants watched a clock and reported the time that they experienced an urge to lift their finger. Because brain activity thought to drive the movement was found to occur earlier than the reported time of the urge, these experiments suggest that we become conscious of our intentions after they have been set in motion. The wider implications of Libet’s investigations into the timing of intentions and the many studies he inspired are still contentious, but his method of measuring the time between the subjective experience of intending and the moment of an action provides a relatively simple way of investigating our conscious experience of intending and its relationship to hypnosis.
Higher order thoughts
Our brains are constantly processing vast quantities of information, yet we are conscious of only a few aspects of this information at a time. Therefore, our unconscious mental activity far surpasses what we are conscious of at any given moment. According to higher order thought theories of consciousness, an unconscious mental state becomes conscious when there is another mental state that is about it. If we accept that, as implied by Libet’s results, intentions can be unconscious. These theories then suggest that whether or not we become conscious of an intention is dependent upon whether or not we have a mental state about that intention. From here we can see how it might be possible to act voluntarily whilst experiencing the act as involuntary. The cold control theory of hypnosis argues that to respond hypnotically is to perform an intentional action whilst maintaining an experience of involuntariness about your action. So, at the unconscious level, the action is intended, but is experienced as involuntary because the mental state that would usually be directed at it to form the conscious experience of intending is inaccurate. By analogy with optical illusions in which conscious experience is not veridical, hypnotic responding might therefore be considered an ‘agentic’ illusion – to respond hypnotically is to consciously (and voluntarily) experience a voluntary act as involuntary.
Hypnotic responding as an ability
Scientific research into hypnosis makes use of hypnosis scales to divide the population by the ability to respond to hypnotic suggestions, or “hypnotisability”. To generate a hypnotisability score, a standardised hypnotic induction is followed by a sequence of suggestions of varying difficulty, and the subject’s response recorded for each suggestion. The resulting score can then be used to assign participants to low, medium, or high hypnotisability categories. If hypnotic responding requires maintaining a conscious experience of involuntariness whilst performing a voluntary act, we might expect these groups to differ in the relationship between their intentions and the conscious experiences that are about them. So, some highly hypnotisable people may be more easily able to avoid having accurate conscious experiences of their intentions because their intentions are less accessible to their conscious mental states. We used Libet’s timing of intention task to explore this hypothesis, asking people of varying hypnotisability to report the position of a fast moving clock hand at the moment they became aware of their intention to lift their finger.
Mindfulness of intentions
We also measured the timing of an intention to move in a group of experienced Buddhist mindfulness meditators. Mindfulness meditation involves the cultivation of awareness of mental states, including intentions, and Buddhist scholars have argued that meditators should have greater access to their intentions and should therefore be aware of their intentions earlier than non-meditators. The figure below shows the time between the moment of the finger movement and the reported time of conscious awareness of the intention to move. As predicted, highly hypnotisable people reported their awareness of intention as occurring late – in fact, after they had actually moved, while less hypnotisable people and mindfulness meditators reported earlier awareness of intentions.
These results are consistent with the suggestion that individuals vary in their conscious access to intentions, and that this variation tracks differences in hypnotisability – the ability to maintain a conscious experience of involuntariness whilst performing a voluntary act. Furthermore, there is evidence that mindfulness meditators are less hypnotisable than non-meditators, raising the possibility that mindfulness meditation may decrease hypnotisability by increasing conscious access to unconscious intentions. These results may inform theories of illnesses in which the experience of voluntariness is disrupted. Notably, a later awareness of intention has also been reported in functional motor disorder (FMD) patients. In FMDs, involuntary actions characteristic of nervous system dysfunction (e.g., tremors) occur in the absence of detectable damage to the nervous system. These disorders have been associated with hypnosis since the 19th century, and this study raises the possibility that they may be attributable to a dysfunction in mechanisms supporting the awareness of unconscious intentions.
Featured image credit: Hypnosis by DavidZydd. CC0 public domain via Pixabay.