OVER-EMPHASIZING THE SPECIFIC FUNCTIONS AND DYSFUNCTIONS
OF THE BODY AND THE BRAIN-MIND ENTAILS TACIT CREATIONISM
Dan J Stein (1)
ORCID: 0000-0001-7218-7810
Randolph M Nesse (2,3)
ORCID: 0000-0003-1768-0949
- SAMRC Unit on Risk & Resilience in Mental Disorders, Dept of
Psychiatry & Neuroscience Institute, University of Cape Town, Cape
Town, South Africa
- Departments of Psychiatry and Psychology, University of Michigan, Ann
Arbor, Michigan, USA
- Center for Evolution and Medicine, Arizona State University, Tempe,
Arizona, USA
Running Title: Function, Dysfunctions and Tacit Creationism
Corresponding author: D Stein
Words: 2619
Figures: 0
Abbreviations: 0
Graphical abstract/text: 0
Dr. Stein has received consultancy honoraria from Discovery Vitality,
Johnson & Johnson, Kanna, L’Oreal, Lundbeck, Orion, Sanofi, Servier,
Takeda and Vistagen.
OVER-EMPHASIZING THE SPECIFIC FUNCTIONS AND DYSFUNCTIONS
OF THE BODY AND THE BRAIN-MIND ENTAILS TACIT CREATIONISM
ABSTRACT
Notions of function and dysfunction are fundamental for neuroscience,
psychology and psychiatry, but remain contentious. We propose that some
of these controversies arise from tacit creationism, which incorrectly
views aspects of evolved systems as if intentionally designed. Many
philosophers agree that “failure to perform a normal function” is
fundamental to the concepts of physical disease and mental disorder.
However, unlike machines and computers, bodies and brain-minds are
variable in multiple respects, and these variations may have advantages
and disadvantages in different environments. Indeed, in the case of
bodies and brain-minds it may be difficult to draw a bright line between
normal and excessive activation of an adaptive defense in a particular
context. The metaphors of body as machine, or the brain-mind as
computer, encourage the notions that components of bodies and
brain-minds have specific functions like those of the parts of machines,
and that disorders have clear boundaries. Rejecting tacit creationism,
and accepting the messy reality of organic complexity, as well as the
fuzzy boundaries of disorder, offers a better way forward for
neuroscience, psychology, and psychiatry.
Keywords: Function, dysfunction, tacit creationism, disease, mental
disorder, philosophy
The notions of function and dysfunction are fundamental for
neuroscience, psychology and psychiatry. However they spur continuing
controversy, with ongoing debate about how best to conceptualize and
operationalize function and dysfunction, including a large body of work
in philosophy of biology, medicine, and psychiatry (Allen et al. ,
1998; Schwartz, 2007; Griffiths & Matthewson, 2018; Keeling et
al. , 2019). Here we propose that some of the controversies about
function and dysfunction arise from tacit creationism, which incorrectly
views aspects of evolved systems as if they were intentionally designed.
Viewing bodies as devised machines, or minds as programmed computers,
leads us astray in important ways.
There is widespread agreement that the concept of function in biology
ultimately depends on how a trait contributes to gene transmission.
Philosophers disagree, however, about the nature of dysfunction and
disease. Boorse, known for his naturalist position, argues that disease
occurs when a part of the body fails to perform its natural function,
which is essential for survival and reproduction (Boorse, 1975, 1997,
2014). In contrast, Wakefield’s definition of disorder as “harmful
dysfunction” is partly normative, and he argues that dysfunction is
present when a trait fails to perform the function for which it was
naturally selected (Wakefield, 1992, 2007; Faucher & Forest, 2021).
Both these positions, as well as many others in philosophy of medicine,
concur that “failure to perform a normal function” is fundamental to
the concept of physical disease. We know that the function of a radiator
is to cool the engine. Thus, when the radiator fails, a car overheats
and malfunctions. Similarly, the heart is a pump and insufficient blood
circulation causes the malfunction we call congestive heart failure,
although this view may well be an oversimplification (Binney, 2018;
Ruse, 2018). However, not all bodily traits have functions as specific
as pumping for the heart. Many traits have multiple functions, and many
functions are served by multiple traits, so expecting each trait to
serve a specific function misrepresents the messy reality of biology and
disease (Nesse & Stein, 2012).
Genes make proteins that make tissues, but the process is very different
from the manufacture of a machine. Machines have blueprints of the ideal
type, but organisms have genomes that vary between individuals. Parts of
a machine tend to be discrete, each with a specific function envisioned
by an engineer. In contrast, many parts of a body have blurry boundaries
and multiple functions. For instance, the immune system includes dozens
of different kinds of cells, many playing multiple roles. Specific genes
and hormones are not regulated via simple feedback systems but instead
by vast networks of molecules, with roles for multiple small RNAs
expressed in response to certain cues, in confoundingly convoluted
sequences of causation.
Many philosophers of psychiatry would similarly concur that “failure to
perform a normal function” is fundamental to the concept of mental
disorders. Furthermore, the advent of the digital age has allowed us to
conceptualize the brain-mind as a computer. Thus mental disorders may be
due to hardware problems (that is, brain defects) or software glitches
(for example, cognitive distortions). However, the brain-mind is an
embodied cognitive-affective processing system, and mental disorders
invariably involve complex interactions of biological and psychological
mechanisms. The term “wetware” may be useful in highlighting this
organic complexity, and steering us away from simplistic computer models
(Stein, 2021).
These distinctions between body and machine have important implications
for our concepts of function and dysfunction. A machine must conform to
an ideal type, as specified by the engineer. In contrast, the body is
variable in multiple respects, and these variations may have advantages
and disadvantages in different environments. Indeed, in the case of
bodies it may be difficult to draw a bright line between normal and
excessive activation of an adaptive defense in a particular context.
Fever is an adaptive response that is helpful in combating infection,
but in some circumstances a high fever may cause seizures, so a
physician may use a drug (such as an antipyretic) to dampen an adaptive
defensive (Nesse, 2023).
In the case of the brain-mind, drawing a bright line between normal and
excessive activation of adaptive defenses may be even more difficult.
Anxiety is an adaptive defense that is useful in the face of threats
(Marks & Nesse, 1994; Stein & Nesse, 2015). However, cues indicate
only that danger might be present, so the optimal system is like a smoke
detector; it has to express many inexpensive false alarms to ensure a
protective response to catastrophic threat (Nesse, 2001). Importantly,
most instances of anxiety are “false alarms” from a normally
functioning control system. Clinicians assess the magnitude of threat
and intensity of distress to judge whether a dysfunction is present, but
excessive anxiety does not necessarily imply that the underlying
mechanisms are defective, and clinicians often sensibly provide
treatment to relieve anxiety even when there is no evidence of system
failure.
Social anxiety offers a special case for debate (Campbell-Sills &
Stein, 2005; Wakefield et al. , 2005). Most people are cautious
when they are the focus of group attention for the good reason that even
a small misstep can rupture relationships or arouse envy or
condemnation. Social anxiety functions to inhibit actions that might
cause social harm, but how much is enough? Should we consider benefits
and costs to kin as well as the individual? Is the current level of
social anxiety too much or too little given this individual’s roles in
this social group at this time and place? Or should we be asking what
aspects of the individual’s behavior are optimally expressed or
inhibited in this situation now? Such questions emphasize the specific
difficulties in determining whether or not mental dysfunction is present
(Bolton, 2008; First & Wakefield, 2013; Stein et al. , 2021), as
well as the more general issues of complexity and vagueness in
psychiatry (Kendler, 2012; Keil et al. , 2017; Fried & Robinaugh,
2020).
Defining what is functional and what is dysfunctional is much harder for
behavior control systems than for parts of a machine. Reifying
constructs such as social anxiety disorder, as if they represent
failures of specific parts in a machine, is a clear example of tacit
creationism. While there are brain mechanisms that regulate social
anxiety, anxiety, and differences that make some brains more vulnerable,
it is increasingly unlikely that excess social anxiety will be found to
arise from specific brain circuitry or neuronal molecules. It is,
instead, a particular state of an organic embodied cognitive-affective
processing system that varies considerably from individual to individual
and from situation to situation in ways that defy attempts to crisply
define function and dysfunction.
Some evolutionary theorists have tried to define “the function” of
depression, or to link distinct subcategories with different functions,
as if they were products of design. However, the varieties of low mood
are states shaped by natural selection because they increase fitness
when they are expressed in a variety of overlapping situations in which
reduced motivation and self-esteem are useful (Nesse, 2019). Emotions
have vague boundaries and overlapping causes, quite different from the
discrete modes that might be triggered in a machine (Nesse & Ellsworth,
2009). In distinguishing between normal low mood and pathological
depression, confidence is possible only for extreme cases, and providing
treatment may be worthwhile even when system disruption is unproven.
We sometimes forget how deeply metaphoric our ordinary language concepts
are (Lakoff & Johnson, 2010). For example, the notion of disease maps
onto a number of different extended metaphors, including disease as
“breakdown”, disease as “imbalance”, or disease as “attack”
(Stein, 2008). The metaphors of body as machine, or the brain-mind as
computer, encourage the notion that components of bodies and brain-minds
have specific functions like those of the parts of machines. They do
serve functions, but many, especially emotions and other aspects of
behavioral control systems, do not have a specific function, unless that
function is very broadly framed as “adjusting the individual’s
cognition, physiology, behavior, and emotions to better cope with
situation X” or as “contributing to gene transmission” (Nesse &
Ellsworth, 2009).
The idea that there are “natural kinds” in biology, akin to the
elements in the periodic table, and analogous to the artefactual kinds
in machines, encourages attempts to define them in terms of necessary
and sufficient criteria (Stein, 2021, 2022). In biology, however, kinds
are often “soft,” with vague outlines, fuzzy borders, and multiple
functions and inordinately complex connections that frustrate efforts to
establishing necessary and sufficient criteria. This is not to diminish
the value of investigating the complex proximal and distal mechanisms
that underlie soft biological kinds, it is rather to emphasize their
complexity (Bechtel & Richardson, 1993; Mitchell, 2003; Wimsatt, 2007),
and the need to avoid tacit creationism.
It may be countered that in the case of a machine, there may also be
dysfunctional states, such as a car not starting, that are due to a
range of different causes. However, when a car does not start, this is
typically due to one or other very specific defect, such as the battery
being dead, or the ignition mechanism not working. In the case of
anxiety and depression, however, a range of different mechanisms may
synchronically and diachronically contribute. Viewing anxiety and
depression as products of a specific defect in a machine obscures the
organic complexity of living systems. The notion that these conditions
are caused by genetic, anatomic, or physiological defects that disrupt a
specific function has been contradicted by decades of research that has
failed to demonstrate specific biomarkers or causes.
Reluctance to give up a view of bodies as machines and brain-minds as
computers is understandable. The metaphor has inspired essential
searches to find specific defects in specific parts that disrupt their
specific functions. In some cases, these searches have paid remarkable
dividends; consider the discovery that pancreatic dysfunction decreases
insulin production and leads to diabetes, which responds to external
administration of insulin. However, in many cases this type of
specificity is not found. In some cases, such as Alzheimer’s dementia,
we can still hope that the search will succeed. But giving up tacit
creationism and accepting the messy reality of organic complexity may
well offer a more fruitful way forward for neuroscience, psychology, and
psychiatry.
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