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Measuring Consciousness 1: Tipping the scales

Perhaps of all the concepts dealt with in Psychology — the conscious experience — is one of the most subjective. In 1889 consciousness was recognised by Stuart Smith as a term “impossible to define except in terms that at unintelligible without grasp of what consciousness means.” Finding the correct scales to use to measure such a thing is, therefore, pretty difficult. Let’s take a look at some of the measures and methods used to determine good subjective scales in consciousness ratings.The recognition of consciousness as a concept is often attributed to the article Essay Concerning Human Understanding, written in the 1680s by physician and philosopher John Locke. Locke recognized that the mind was a blank slate (tabula rasa) until experience determines what we think and know. The use of “consciousness” as a word, however, dates back far beyond Locke’s reach being derived from the Latin for “knowing onself”.

Philosophers continue to differ in their opinion of what consciousness is even today. A British philosopher of the 20th century, Gilbert Ryle, once argued that consciousness actually depends on separating the mind from the body (in what is known as cartesian dualism; dualism being the position that mental occurrences are sometimes non-physical, most commonly associated with Rene Descartes) and thus we forget that consciousness might just be seen as a result of behavioral and linguistic understandings.
More recently, the American philosopher Ned Joel Block has argued for the existence of two types of conscious experience (phenomenal or p, and access or a). Phenomenal consciousness is pure experience of sounds, sensations, emotions, and feeling, while access consciousness is the experiences we have that require verbal report, reasoning, and executive function (controlling behaviour). While some philosophers dispute the validity of this distinction (how can you separate reasoning and emotion, for example?) many have accepted the principle. Indeed, further to the two identified here some have argued for up to eight distinct areas of consciousness.
The fact that there is no clear and agreed upon definition of consciousness reflects in the measurements used when considering measuring consciousness. Perhaps by far and away the most reliable measure is subjective conscious ratings.
What is a subjective consciousness rating?
Most often it is a scale or questionnaire asking participants to rate the clarity or quality of their experience in some way. Because subjective scales will different from person to person, the best way to evaluate their usefulness is to compare them using one of two methods:

1. Zero-correlation criterion: this looking for correlations [maybe define this in glossary] between performance (an objective measure) with self-reported awareness (a subjective measure) across different conditions. In zero-correlation criterion any positive relationship between performance and awareness suggests the involvement of at least some conscious knowledge in the decision that has been made in a task the experimenter sets.
2. Guessing criterion: this is where participants claim to be guessing or performing randomly in a task; if they actually perform above chance then their performance is based on knowledge they are not aware of. An important thing to realise about the guessing criterion is that above-chance performance could also be an indication of the test failing to be exhaustive. Given this, the best that can be done is to consider scales on a gradient where one scale may indicate less unconscious processing than another.

We look for scales that are both exhaustive (should define) and sensitive when evaluating scales of consciousness ratings. Both techniques are widely used, however, there are a number of issues with verbal/written report worth noting when considering use, not least of which is that these ratings are open to dishonesty. Most of the time this is unintentional on the part of the participant, but will cause noise in the data regardless. More recently studies have found that we are not only unreliable in reports, but can confuse our own actions for others’ in certain situations. Goldberg recently found up to 63 percent of participants will accidentally “steal” an idea from a group discussion and remember it as their own.
Thus measuring consciousness continues to be a difficult procedure. In more medical studies, the use of brain activity and arousal may be used alongside these ratings to get a more accurate measure of consciousness. However, these techniques are costly and laborious both for the experimenter and participants.

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