The Biological Evolution of ConsciousnessThis raises the possibility that, even if phenomenal consciousness has a function, that function
can also be performed by non-conscious systems. If so, phenomenal consciousness may still
have been selected for because of the function it performs, but this is just a contingent fact of
evolutionary history. If evolutionary history had stumbled on a different, non-conscious way of
performing the same function, we might have evolved to be zombies—entirely non-conscious
creatures who behave indistinguishably from us. As if this were not unsettling enough, the possi-
bility that the putative function of consciousness be performed by a non-conscious system raises
another general problem for adaptationism about phenomenal consciousness.
Any candidate function of phenomenal consciousness might simply be a function of some
other capacity or system that merely correlates with phenomenal consciousness. The putative
functions of phenomenal consciousness that different theorists have proposed are undoubtedly
important features of our psychology, and it may be that they are intimately related to phenome-
nal consciousness even if they are not themselves functions of phenomenal consciousness. In each
case, it seems possible for these functions to be fulfilled in the complete absence of phenomenal
consciousness. If that possibility obtains, these functions are performed by non-conscious cor-
relates of phenomenal consciousness, and thus phenomenal consciousness per se plays no causal
role in their performance. Perhaps because of this, some contemporary theories of consciousness
have abandoned the strategy of positing a function of consciousness altogether. Nevertheless, it
will be instructive to look in a bit more detail at some influential theories of consciousness that
do have something positive to say about its function.
According to Global Workspace Theory and other theories like it, the function of conscious-
ness is to make information available to the entire cognitive system, and consciousness simply
is the availability of that information (Baars 1988). When information is globally available, the
organism can flexibly act on the basis of that information, and the organism is phenomenally
conscious. What it’s like to be that organism is simply what it’s like to have all of that information
available to one’s entire cognitive system.
A rival theory is Supramodular Interaction Theory (Morsella 2005), according to which the
function of consciousness is to integrate different sources of information so as to select adaptive
action. Sometimes information from different sources is compatible with multiple interpreta-
tions or actions. Consider the McGurk effect: the same visual information (a person moving
their lips in a certain way) gives rise to different interpretations of what the person is saying,
depending on the auditory information that co-occurs with the visual stimulus (whether a
voice is heard saying the syllables “bah,” “dah,” or “gah”). This conflict is resolved automatically
and unconsciously. Other conflicts cannot be resolved automatically and unconsciously, and on
this theory, the function of consciousness is to allow organisms to resolve conflicts that involve
instrumental action. For example, the pain a person feels while holding a hot plate informs the
choice of whether to continue holding the plate or drop it. The choice is not automatic, and the
person needs the conscious states of hunger and pain to weigh the cost of not eating versus the
cost of potential tissue damage.
A third alternative is Flexible Response Mechanism Theory (Earl 2014). According to this
theory, the function of consciousness is neither global availability nor integration of information.
The function of consciousness is to provide organisms with input to their Flexible Response
Mechanism—an executive mechanism by which responses to disparate stimuli can be made in a
deliberate manner. For example, breaking a habit such as cigarette smoking requires inputs from
a variety of sources, such as anticipating feeling good about quitting, memories of the bad health
effects of smoking, or intending to keep a promise to a family member. Such inputs are given to
the Flexible Response Mechanism, which can (in principle, if not always in practice) override
the automatic, habit-driven behavior.