One of the most well-known examples of plasticity in psychology is the London taxi driver study, which showed that years of navigating complex city streets physically enlarged a specific part of drivers’ brains. But this is just one illustration of a broader principle: the brain continuously reshapes itself in response to experience, injury, and learning throughout life. Plasticity shows up in dozens of real-world scenarios, from recovering speech after a stroke to learning a musical instrument as a child.
What Plasticity Means in Psychology
Plasticity refers to the brain’s ability to change its structure and function in response to experience or damage. It operates through two main mechanisms. The first is structural change, where neurons form new connections, strengthen existing ones, or even generate entirely new cells. The second is functional reorganization, where undamaged parts of the brain take over jobs that were handled by damaged regions.
These aren’t rare, dramatic events. Plasticity is happening constantly. Every time you learn a new skill, memorize a fact, or adjust to a change in your environment, your brain is physically rewiring itself at the level of individual synapses, the tiny gaps where neurons communicate with each other.
The London Taxi Driver Study
The most frequently cited example of plasticity comes from a study published in the Proceedings of the National Academy of Sciences. Researchers scanned the brains of London taxi drivers and compared them to control subjects. The posterior hippocampus, a brain region critical for spatial memory and navigation, was significantly larger in taxi drivers than in people who didn’t navigate for a living.
What made this finding especially compelling was the dose-response relationship. The longer someone had worked as a taxi driver, the larger their right posterior hippocampus became, with a clear positive correlation (r = 0.6). At the same time, a more anterior section of the hippocampus actually shrank with experience, suggesting the brain was reallocating resources rather than simply growing overall. Total hippocampal volume was roughly the same between groups. The brain wasn’t getting bigger; it was reshaping itself to meet the demands placed on it.
How the Brain Rewires After a Stroke
Stroke recovery provides one of the most dramatic examples of functional reorganization. When a stroke destroys part of the primary motor cortex, the region that controls voluntary movement, other brain areas can step in. Secondary motor areas like the supplementary motor area and premotor cortex have their own direct connections to the spinal cord, giving them the raw infrastructure to control movement even though that wasn’t their primary role.
Brain imaging studies show a consistent pattern. In the weeks after a stroke, the undamaged hemisphere of the brain becomes unusually active during movements of the affected side of the body. People with more severe strokes recruit these backup areas more heavily. Over time, as recovery progresses, the brain gradually shifts control back toward the damaged hemisphere and reduces its reliance on secondary areas. In one study, extra brain regions recruited 10 to 14 days after stroke had gone quiet by the three-month follow-up.
This doesn’t mean recovery is guaranteed or complete, but it illustrates how the brain actively reorganizes to compensate for lost tissue.
Blind Braille Readers Use Their Visual Cortex
In people who lost their sight early in life, the visual cortex doesn’t simply go dark. Brain scans of blind Braille readers revealed that their primary visual cortex, the region normally dedicated to processing what the eyes see, activated strongly during tactile discrimination tasks like reading Braille. Sighted control subjects showed the opposite pattern: their visual cortex actually deactivated during the same touch-based tasks.
Importantly, a simple touch that didn’t require any discrimination produced no visual cortex activation in either group. The brain wasn’t just passively responding to touch. It was actively recruiting unused visual processing areas to handle a complex sensory task. This is a textbook case of vicariation, where a brain region takes on a function it was never originally designed for.
Musical Training Reshapes the Brain
Learning to play an instrument, especially during childhood, triggers widespread structural changes. Musicians show altered cortical thickness in motor areas on both sides of the brain, along with changes in the corpus callosum (the bridge connecting the two hemispheres) and the primary auditory region. The changes extend well beyond areas you might expect: frontal regions involved in planning and decision-making also show measurable differences.
The timing of training matters. Childhood practice correlates with increased white matter integrity in pathways connecting motor and sensory areas. Adolescent practice strengthens connections between the hemispheres through different parts of the corpus callosum. Adult practice correlates with changes in yet another set of fiber bundles. The brain doesn’t just change once; it continues to reshape itself based on when and how much you practice, with different structures responding at different life stages.
Plasticity at the Cellular Level
Behind all these large-scale examples is a molecular process. When you learn something, the connections between neurons either strengthen or weaken. Strengthening, called long-term potentiation, happens when two neurons fire together repeatedly. The receiving neuron responds by inserting more receptor proteins into its surface, making it more sensitive to future signals from that same partner. The reverse process, long-term depression, weakens connections through low-frequency activity and removes those same receptors. Together, these two mechanisms are thought to be the cellular foundation of memory formation.
The adult brain also produces new neurons, though in a limited way. Research using a clever technique that measured carbon-14 from Cold War nuclear testing in human brain cells estimated that roughly 700 new neurons are added to each hippocampus every day in adults, replacing about 1.75% of the neurons in that region each year. This adult neurogenesis is modest compared to what happens during development, but it provides a continuous source of fresh cells in the brain’s primary memory hub.
Developmental Plasticity in Children
The brain is most plastic during childhood, and one reason is sheer abundance. Synaptic density in the cerebral cortex increases rapidly after birth, peaking around age 1 to 2 at roughly 50% above adult levels. From there, unused connections are selectively eliminated through adolescence, a process called synaptic pruning that refines coarse neural maps into efficient, mature circuits.
This is why children recover from brain injuries far more effectively than adults. The 19th-century neurologist Pierre Paul Broca observed that children who suffered damage to their left hemisphere could relearn speech much more readily than adults with the same injury. The developing brain has enough redundancy and flexibility that the opposite hemisphere can take over lost functions, a capacity that diminishes as circuits become specialized with age.
When Plasticity Works Against You
Not all plasticity is beneficial. After an amputation, the brain region that previously received input from the missing limb doesn’t stay idle. Neighboring regions expand into that territory, and this cortical remapping is closely correlated with phantom limb pain, the sensation of pain in a limb that no longer exists. The more extensive the remapping, the worse the pain tends to be.
The mechanisms behind this maladaptive plasticity include a loss of inhibitory signaling, changes in how neurons strengthen their connections, and physical sprouting of new axon branches. People who experienced chronic pain before the amputation tend to have more severe phantom pain afterward, suggesting the brain had already begun maladaptive rewiring before the limb was lost. Similar processes are thought to contribute to chronic pain conditions and tinnitus, where the brain essentially learns to generate a sensation that has no external source.
Bilingualism and Cognitive Reserve
Speaking two languages throughout life places constant demands on the brain’s executive function system. Every time a bilingual person speaks, their brain must select the correct language and suppress interference from the other. This lifelong mental exercise appears to build what researchers call cognitive reserve, a buffer against age-related cognitive decline.
Young adult bilinguals generally have greater grey matter volume than monolinguals. As bilinguals age, their brain structure actually deteriorates faster than that of monolinguals, yet their cognitive performance remains comparable. In studies of patients with Alzheimer’s disease, bilingual patients matched to monolinguals on clinical impairment showed significantly more brain atrophy and poorer metabolic activity on brain scans. In other words, their brains were in worse physical shape, but they were functioning at the same level. The years of managing two languages had built a neural reserve that allowed them to tolerate more damage before symptoms appeared.