Myth #1: Brain Power: Myths, Hemispheres, and Evidence
Myth #1: We Use Only 10% of Our Brain
The popular question and widespread belief
Many people, including some psychology students and neuroscientists, have encountered or believed the claim that “we only use 10% of our brain.” This widespread belief persists in media, marketing, and general public discourse.
The myth is appealing, often leading to disappointment when neuroscientists debunk it. Studies indicate that a significant portion of educated adults endorse it, such as about one-third of psychology majors (10\% endorsement) and approximately 59\% of college-educated individuals in Brazil.
Even some misinformed neuroscientists have endorsed this claim.
The myth's persistence is partly attributed to media and marketing narratives that promise self-improvement or increased cognitive power by unlocking this "unused" brain capacity.
Illustrative examples include references in self-help literature that suggest dramatic cognitive enhancement is possible.
The phrase frequently appears in discussions about brain optimization, sometimes framed as a comforting thought or a hopeful shortcut to greater intellect or productivity.
Core Debunking Points from Neuroscience
No evidence for dormant brain tissue
There is no scientific evidence supporting the idea of a large, dormant fraction of brain tissue awaiting activation.
Brain imaging and functional mapping extensively demonstrate that almost all cognitive tasks recruit widely distributed networks, involving many brain areas.
If significant portions of the brain were truly unused, injury or degeneration in specific areas would not result in predictable deficits.
In reality, conditions like strokes, head trauma, or localized brain damage reliably produce measurable deficits, affecting thoughts, perception, memory, or emotion, which indicates the functional importance of diverse brain regions.
Modern brain technologies such as Electroencephalography (EEG), Positron Emission Tomography (PET), and Magnetic Resonance Imaging (MRI) map many psychological functions to specific brain regions.
These technologies show no evidence of a vast “silent” or unused cortex waiting to be activated. Instead, tasks typically recruit processing across the entire brain rather than isolating it to a single “base” region.
When parts of the brain are underused due to injury or disease, the tissue tends to degenerate or be taken over by adjacent areas. This contradicts the notion of a stable reserve of quiet brain tissue.
The interpretation of glial cells
While glial cells significantly outnumber neurons (with a neuron-to-glia ratio of approximately 10:1), their primary roles are support and housekeeping for neurons.
Glial cells do not function as a latent pool of cognitive power; neurons remain the primary agents of information processing.
Historical context and motives
The myth has a historical backdrop and persists because it offers a simple, enticing story that may promote self-improvement or creative thinking.
Despite its appeal, the myth completely lacks empirical scientific support.
Terri Schiavo Case: A Cautionary Example
The impact of severe brain damage
Terri Schiavo suffered severe oxygen deprivation after a cardiac arrest, which resulted in the destruction of roughly 50\% of her cerebrum.
The cerebrum is the brain region critically associated with conscious awareness, complex thought, and voluntary actions. The extensive damage to this region demonstrated that losing a substantial portion of the brain leads to profound and permanent loss of core cognitive functions, not that 50% was "unused" tissue. Her case exemplifies that far from having large unused portions, significant brain tissue loss has devastating consequences, underscoring the functional importance of most brain areas for consciousness and basic life functions.