Consciousness

Chapter

Eight

Conscious and unconscious

Another problem stems from the behaviourist suspicion of verbal reports, with
some wanting more reliable, ‘objective’ measures of consciousness than what
people say. But this is a rather curious idea. On the one hand, making a verbal
report by speaking or writing is just as much an objective action as is pressing a
button or pointing. For this reason, we will not refer to verbal reports as ‘subjec-
tive measures’, as some writers do. But on the other hand, if all objective measures
of discrimination are taken as evidence of conscious perception, then evidence for
unconscious perception seems to be ruled out by definition (Kihlstrom, 1996). In
other words, this move would define away the whole idea that people might be
able to demonstrate, by their behaviour, detection of stimuli which they said they
were not conscious of.

This mathematical theory requires two variables
to explain how people detect things like sounds,
flashes of light, or touches on the skin. One variable
(d’ or d-prime) is the person’s sensitivity (how good
their eyes are, how acute their hearing is). The other,
β, is their response criterion (how willing they are to
say ‘yes, I  see it’ when they are unsure). These two
can vary independently of each other.

Most relevant here is that without their realising it,
and with exactly the same sensitivity, people can
apply a different criterion. For example, if there is
a financial incentive to detect a light flash and no
penalty for a false positive, then most people will
set a very lax criterion, but if saying ‘I see it’ when it’s not there makes them look
stupid or lose money, then they set their criterion much higher.

This means that there is no fixed threshold (or limen) that separates the things
that are ‘really seen’ or ‘really experienced’ from those that are not. It implies, once
again, a difficulty with the idea that things are unequivocally either ‘in’ conscious-
ness or ‘out’ of consciousness, and makes the concepts of subliminal and supra-
liminal perception much more complicated. Some have argued for abandoning
the term ‘subliminal’ altogether in favour of ‘implicit’ or ‘unconscious’, but this does
not really solve the problem, and generally the term has been retained.

Hit

NOISE d′ SIGNAL+NOISE

False positive

Internal response

Criterion

‘no’ region ‘yes’ region

Correct

rejection

Miss

PRACTICE 8.1

DID I DO THIS CONSCIOUSLY?

As many times as you can, every day, ask yourself ‘Did I do this consciously?’

You might get out of bed, put on a T-shirt, pick up your toothbrush, or carry

out any number of small actions. After any of these, ask the question.

Does asking the question itself make a difference?

FIGURE 8.1 • Signal detection theory shows how

to measure the ability to detect

a signal embedded in noise, such

as when we try to hear a faint

sound or see a briefly flashed

word or letter, and replaces the

idea of a fixed threshold. The left

curve represents just noise and

the right curve noise plus signal,

and the task is to decide whether

there is really a signal or not.

A person’s criterion may shift even

if their sensitivity (d′) does not.

Areas under the curves show the

proportion of hits, misses, correct

rejections, and false positives.