 26. Naturalizing the Self 575
es and reflects? To address this issue, one 
promising avenue of research is the increas -
ing use of transcranial magnetic stimulation 
(TMS), which uses a powerful yet noninva -
sive magnet to alter or suppress activity in 
a specific region, providing a stronger basis 
for making causal inferences than brain im -
aging techniques. For example, Luber, Lou, 
Keenan, and Lisanby (2012) found that sup -
pressing activity in the mPFC using TMS led 
to a reversal of the self-  enhancement effect, 
providing causal support for the claim that 
the mPFC plays a role in self-  evaluative pro -
cesses (see also Kwan et al., 2007).
Finally, the research to date does not 
conclusively demonstrate that there are any 
brain networks linked to self processes that 
are physically and functionally distinct from 
those used for more general-  purpose cogni -
tive processing (e.g., processing information 
about other people; Beer, 2016). In other 
words, there is little evidence for a self- 
specific module or network in the brain. As 
a result, the field may be moving away from 
essentialism, which asks where in the brain 
psychological phenomena are located, to -
ward a constructivist approach, which asks 
how the brain creates perceptions, beliefs, 
feelings, and actions (Barrett, 2017).
At least in principle, new knowledge 
about the brain can help us refine our theo -
retical conception of the self and self-  related 
processes. A basic premise of the naturalist 
approach is that the way we conceptualize 
the self should be consistent with, and con -
strained by, what we know about how the 
brain works. For example, if one function 
of the self is to coordinate and regulate in -
ternal body signals and behavioral responses 
(i.e., self-  regulation), then the brain should 
be doing something different when the self is 
“in control” than when it is “out of control.” 
If one motive governing the self system is 
self- enhancement, then there must be some 
neural mechanism that “tags” the valence of 
a self-  relevant experience and causes posi -
tive experiences to be encoded more deeply 
than negative ones. And, if there is selec -
tive retrieval of positive (vs. negative) auto -
biographical memories, then there should 
be identifiable neural processes that enables 
this to occur (e.g., preferential pathways 
to representations tagged as positively va -
lenced).Clearly, we have a long way to go before 
we truly understand the neural mechanisms 
underlying these and other aspects of the 
self. However, the advancing methods of 
neuroscience hold a great deal of promise 
and could ultimately lead to discoveries that 
provide a stronger foundation for a natural -
ist view of the self.
Is the Self a Product of Evolution?
The eminent geneticist Theodosius Dobzhan -
sky (1964) remarked that the self is the chief 
evolutionary novelty possessed by humans. 
Evidence that self-  esteem and other self pro -
cesses are moderately heritable (e.g., Cai & 
Luo, 2017; Neiss et al., 2005) is consistent 
with an evolutionary account of the self. 
However, there are four possible interpreta -
tions. First, the self may be “genetic junk,” a 
characteristic that neither contributes to nor 
detracts from the organism’s fitness but is 
nonetheless passed on to succeeding genera -
tions. A second possibility is that the self is 
a functionless by-  product of another adapta -
tion that does not solve any adaptive prob -
lems on its own but is carried along with the 
more functional characteristic. For example, 
the self has been described as an incidental 
by- product of high-level intelligence and 
complex sensory processing associated with 
large brains.
However, it is difficult to write off the 
self as an evolutionary accident or a func -
tionless by-  product. As much as any other 
component of the mind, the self fulfills the 
criteria of an adaptive design as outlined by 
Williams (1966): It is universal, complex, 
reliably developing, well engineered, and 
reproduction promoting. Aspects of the self 
are clearly universal (i.e., species-  typical); 
although there is individual variability in 
self- awareness and self-  representations, all 
humans have both capacities. The self is also 
clearly complex, reliably developing, and, as 
I argue subsequently, promotes survival and 
reproduction.
Yet even if the self meets the criteria of 
adaptive design, it may not be an adapta -
tion in the technical sense but rather an 
“exaptation”—a characteristic that was se -
lected for a different purpose than its cur -
rent function; for example, a fly’s wings 
were originally selected for thermoregula -