language that one can communicate sufficiently well with another being to establish
whether it is conscious. Without language, he suggests, the only defensible option is
agnosticism or doubt. Jaynes (1990) by contrast, argued that human language is a
necessary condition for consciousness. And Humphrey (1983) adopted a similar view,
arguing that consciousness emerged only when humans developed a “theory of mind.”
He accepts that we might find it useful for our own ethical purposes to treat other
animals as if they were conscious, but without self-consciousness of the kind provided
by a human “theory of mind” they really have no consciousness at all! There are
other, modern variants of this position (e.g. Carruthers, 1998) but we do not need an
exhaustive survey. It is enough to note that thinkers of very different persuasions have
held this view. Early versions of this position appear to be largely informed by
theological doctrine; later versions are based on the supposition that higher mental
processes of the kinds unique to humans are necessary for consciousness of any kind.
In my book Understanding Consciousness, I argue that this extreme position has little
to recommend it when applied to humans, let alone other animals. Phenomenal
consciousness in humans is constructed from different exteroceptive and interoceptive
resources and is composed of different “experiential materials” (what we see, hear,
touch, taste, smell, feel and so on). It is true that our higher cognitive functions also
have manifestations in experience, for example, in the form of verbal thoughts.
Consequently, without language and the ability to reason, such thoughts would no
longer be a part of what we experience (in the form of “inner speech”). But one can
lose some sensory and even mental capacities while other capacities remain intact (in
cases of sensory impairment, aphasia, agnosia and so on). And there is no scientific
evidence to support the view that language, the ability to reason and a theory of mind
are necessary conditions for visual, auditory and other sensory experiences. Applied
to humans, this view is in any case highly counterintuitive. If true, we would have to
believe that, prior to the development of language and other higher cognitive
functions, babies experience neither pleasure nor pain, and that their cries and
chuckles are just the nonconscious output of small biological machines. We would
also have to accept that autistic children without a “theory of mind” never have any
conscious experience! To any parent, such views are absurd.
Such views confuse the necessary conditions for the existence of consciousness with
the added conditions required to support its many forms . Consciousness in humans
appears to be regulated by global arousal systems, modulated by attentional systems
that decide which representations (of the external world, body and mind/brain itself)
are to receive focal attention. Neural representations, arousal systems and mechanisms
governing attention are found in many other animals (Jerison, 1985). Other animals
have sense organs that detect environmental information and perceptual and cognitive
processes that analyse and organise that information. Many animals are also able to
communicate and live in complex emotional and social worlds (Dawkins, 1998,
Panksepp, 2007). Overall, the precise mix of sensory, perceptual, cognitive and social
processes found in each species is likely to be species-specific. Given this, it might be
reasonable to suppose that only humans can have full human consciousness. But it is
equally reasonable to suppose that some non-human animals have unique, non-human
forms of consciousness.