Chapter
Eight
Conscious and unconscious
the further the stimulus moves from [i.e. below] the subjective threshold, the less
likely it is to be subject to semantic analysis’ (1996, pp. 38–39). This is just one
example showing that the effects of stimuli can differ when they are above or
below different thresholds.
This idea of two thresholds creates difficulties if we think that all processes
must be either conscious or unconscious. We can also go one step further and
suggest that if human behaviour is controlled by multiple parallel systems
without an inner controller or central self in charge, then we might expect to
find different systems responding at many different thresholds, rather than just
two. So, when thinking about implicit, unconscious, or subliminal processes,
we must remember that there may be many thresholds, none of them fixed or
unvarying.
The fascination and fear of the subliminal took a popular turn in 1957 when James
Vicary claimed to have massively increased sales of Coke and popcorn by flashing
the messages ‘Drink Coca-Cola’ or ‘Hungry? Eat Popcorn’ very briefly during a film.
Vicary’s study seems to have been a publicity hoax, but many people still fear
the power of subliminal advertising. And subliminal messages may have small
effects. For example, priming thirsty participants with brand names can affect
their intention to drink a particular brand of drink (Karremans, Stroebe, and Claus,
2006). However, the effects on actual behaviour seem to be weak (Dijksterhuis,
Aarts, and Smith, 2005).
Also popular is the idea that subliminal self-help programmes can reduce anxiety,
improve self-esteem, health, and memory, or help people to give up smoking or
lose weight. Software designed to insert subliminal messages while you sleep,
work, or play games is also commercially available. There is evidence of a placebo
effect that depends on what the label says rather than what is inside; this may
explain why people keep buying them, but there is no evidence of an effect of
the messages themselves. Merikle concludes that ‘There is simply no evidence
that regular listening to subliminal audio self-help tapes or regular viewing of
subliminal video self-help tapes is an effective method for overcoming problems
or improving skills’ (2000, p. 499).
The question about thresholds of awareness becomes crucial in the case of
anaesthesia. In ordinary medical practice, one in every thousand to two thousand
patients has general anaesthetic wrongly administered or monitored, and expe-
riences some awareness during anaesthesia. In the worst cases, patients experi-
ence severe pain and fear but can do nothing to make their state known. This is
somewhat like locked-in syndrome but is at least temporary. The very possibility
of ‘unintended intra-operative awareness’ was long denied, but improved under-
standing of the four separable functions of anaesthetic – paralysis, pain-numbing,
amnesia, and loss of consciousness – mean that it is now generally accepted, and
great efforts are made to prevent it happening.
Being unresponsive and amnesic under anaesthetic is not necessarily the same
as being rendered unconscious (Alkire, Hudetz, and Tononi, 2008). A somewhat
unnerving effect was found in a controversial study of people undergoing gen-
eral anaesthesia (Levinson, 1965). A mock crisis was staged during a real opera-
tion by the experimenter reading out a statement to the effect that the patient
‘subliminal self-help
messages do not have
any effect at all’(Dijksterhuis, Aarts, and Smith,
2005, p. 77)