Modeling and controlling the body in maladaptive ways  9
Discussion
Current theories of predictive processing and active inference 
assume that, to steer adaptive perception and action, the brain 
forms internal generative models of the environment and of the 
body within it. Various studies reveal that the brain has rich 
models of the body; for example, it integrates somatosensory 
and proprioceptive information into a coherent representation 
of things like body size and limb position—i.e. a “body schema.” 
More recently, this model-based perspective has been extended to 
interoception—and the rich sensations we constantly receive from 
the internal body. Theories of interoceptive processing propose 
that the brain continuously estimates key bodily and homeo-
static variables, such as thirst or fatigue levels, perhaps forming 
something like an “interoceptive schema.”
A key reason for forming bodily or interoceptive models is 
that they permit us to exert accurate control over the variety of 
signals (e.g. somatosensory and interoceptive) that the body pro-
duces. Forming an accurate body schema is prominent for motor 
control, whereas modeling interoceptive variables (e.g. thirst) 
is key to keeping them under control by engaging autonomic 
reflexes (e.g. vasodilation) and allostatic or goal-directed actions 
(e.g. drinking) when they have incorrect values. The generative 
modeling perspective can also be extended hierarchically to con-
sider richer models of multimodal experiences and “embodied 
self” that persists in time and anchors our experiences, permit-
ting us to select adaptive courses of action to achieve our favorite
goals.
While it seems obvious that controlling bodily variables and 
achieving goals are crucial for survival, this perspective poses a 
fundamental challenge. In control theory and active inference, 
“controlling” the body ensures that the body generates the pre-
ferred outcomes with high (hedonic or pragmatic) value, e.g. safe 
levels for thirst and fatigue. This idea applies naturally to many 
of our activities that pursue some form of biologically adaptive 
function or well-being, such as ensuring that we keep our bodies 
healthy and consume good food (Sterling and Eyer 1988 , Sterling 
2012). However, it fails to explain why we engage in some activi-
ties 
that are apparently maladaptive and contradict our primary 
biological imperative to ensure body health. Perhaps the most 
puzzling examples are pathological behaviors (e.g. non-suicidal 
self-harm or starvation), which are common across psychopatho-
logical conditions. In these cases, the control exerted over the 
body and its sensations might serve the purpose of generating out-
comes with high (hedonic or pragmatic) values that nevertheless 
run against our homeostatic and survival imperatives (e.g. pain 
and excessive levels of hunger).
In this article, we started with formal accounts of brain pro-
cessing based on active inference to discuss the mechanisms and 
functional purpose of the (apparently) maladaptive ways to “con-
trol the body” that arise in these and other psychopathological 
behaviors. We first discussed how we build models of the world, 
of our bodily and interoceptive processes, of our emotions, and 
of the embodied self, which provides a sense of understanding of 
reality and affords adaptive control at many levels, from the allo-
static regulation of our physiological states to the achievement of 
our individual and social goals. Then, we discussed under which 
conditions we can become highly uncertain about our current 
state and the future course of action. These conditions include 
both contextual factors (e.g. periods of noteworthy changes or 
stress) and factors related to the person’s internal models (e.g. 
poor models in which precision parameters are incorrectly set). 
We next turned to active inference and discussed how reduc-
ing uncertainty (not just maximizing utility) is a key imperative