Plasticity: It’s Time to Rethink the Notion That Intelligence Is Fixed

Revealing Studies Demonstrate Our Brain's Plasticity

By Richard Restak, MD, The George Washington University School of Medicine and Health Sciences
Edited by Kate Findley and proofread by Angela Shoemaker, Wondrium Daily

You may have grown up believing that intelligence was fixed—something we’re born with, like eye color. But there has been a revolutionary transformation in our thinking: Intelligence is not a fixed trait, but can be modified over a lifespan. Richard Restak, Clinical Professor of Neurology at The George Washington University School of Medicine and Health Sciences, shared the latest research on brain plasticity with us at The Great Courses.  

Digital brain concpet image with vague digits and dark background
Brain research shows that one of the aspects of plasticity includes the ability to add new nerve cells, creating alternative circuits to compensate for lost or injured areas. Photo by Wangbar / Shutterstock

Plasticity and Abstract Thinking

Some of our earliest evidence of plasticity comes from research conducted by James Flynn.

Flynn, an intelligence researcher at the University of Otago in Dunedin, New Zealand, demonstrated that from 1947 to 2002, Americans improved their IQ scores by 24 points on testing for similarities. In the similarities section, subjects are given two items (for instance, milk and orange juice) and asked to describe what these items have in common. 

This change in IQ arises because we’re using our intelligence in different ways. 

In agrarian and hunter societies, intelligence was practical and literal. But thanks to urbanization, education, and the permeation of scientific thinking into our everyday lives, we now can move beyond thinking only about the “here and now.” Instead, we can work with concepts that involve abstraction.

Intelligence today involves the ability to think outside the bounds of personal observation and experience. Proverbs are good examples of this. 

“A rolling stone gathers no moss” is not really about stones or moss; it’s conveying the idea that one has to keep moving in order to do well in life. “People in glass houses shouldn’t throw stones” means that you shouldn’t criticize people for things that actually refer to yourself as well. 

Some researchers proposed that the change from literal to abstract thinking was influenced by genetics. However, Flynn thought genetic changes could not account for the increase; there simply wasn’t enough time.

Instead, he proposed that intelligence is related to cultural forces. He demonstrated how twin studies favoring genetics are flawed.  

What Twin Studies Revealed about Intelligence

Flynn uses an interesting analogy taken from basketball. In this example, two twins separated at birth are both very tall and have no initial interest in basketball, but get encouraged to play the sport because of their height. Eventually, they both end up in the NBA. 

Some people might erroneously conclude that they followed the same life path solely because of their similar genetics, when in fact, external factors were at play. As Flynn illustrates, “There is a strong tendency for a genetic advantage (such as tallness) to get more and more matched to a corresponding environment.” 

Flynn concluded that the environment plays a great role in enhancing our cognitive powers. It is important for us to seek challenging cognitive environments.

We can increase our intelligence by solving math problems, interpreting literature, finding on-the-spot solutions, assimilating the scientific worldview, and practicing wisdom. 

Science of Plasticity

Brain research was revolutionized by the discovery of plasticity. Plasticity refers to all of the changes in the structure and function of the brain such as neurogenesis, which is the brain’s ability to add new nerve cells. 

The science of plasticity is simple: 

(1) When you exercise your brain, you release natural growth factors and influence neurotransmitters, which enhance your brain’s level of performance. 

(2) The efficiency of cell-to-cell communication via chemical messengers increases. 

(3) There is a remapping of the functional connections among neurons, as new things are learned, new maps are created, or old maps altered. 

(4) Alternative circuits can be established to compensate for lost or injured areas. 

How Environment Impacts Plasticity

Much of what we’ve learned about plasticity comes from animal research in enriched environments. William Greenough of the University of Illinois at Champaign-Urbana worked in the 1970s with two groups of rats. 

One group of rats was isolated from other rats and didn’t receive any stimulating activities all day long. The second group was in what Greenough called the rat equivalent of Disneyland: They had toys, wheels, and interactions with other rats. They were more socially and physically active. 

Under the microscope, 25 percent more synapses per neuron were found in the second group of rats. They had a greater brain volume and improved learning. Best of all, this correlation continued across the lifespan. 

Although rats are obviously not the same as humans, other studies have shown that an enriched environment does indeed lead to enhancement in the human brain.

The Bucharest Early Intervention Project compared abandoned children reared in institutions to abandoned children moved from the institutions to be raised in foster care. Their cognitive development was tracked over 54 months. 

The cognitive development of children who remained in institutions remained far below that of children moved to foster care. The younger the child when placed in foster care, the better the result. The latter demonstrates how during the first two years of life, the brain has a high degree of plasticity and will be shaped according to experience.

Can Dyslexia Be Improved?

However, the effects of environmental enrichment on the brain are not limited to infancy, as a recent study on dyslexia indicates. 

In 2009, Marcel Just and Tim Keller of Carnegie Mellon carried out a research project involving dyslexic children between ages eight and ten. They introduced a reading remediation program lasting only six months, but it led to an increase in white matter in the areas of the brain responsible for language. 

Thirty-seven struggling readers received remedial instruction, while 12 did not. The white matter changes occurred only in the remedial group. 

Anatomical changes coincided with the improvements in reading. This is what’s called a brain-behavior correlation, where a change in brain structure or function corresponds to a behavioral change.

Even modest modifications in white matter may enable major changes in cognitive ability, as Just and Keller claim in their paper documenting results from the study, which was published in the journal Neuron. According to Dr. Just, this study provided evidence that repeated cognitive exercises can alter the connectivity of the human brain. 

These studies illustrate a fundamental principle: We sculpt our brains according to our life experiences. 

This article was edited by Kate Findley, Writer for Wondrium Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for Wondrium Daily.
Dr. Richard Restak is Clinical Professor of Neurology at The George Washington University School of Medicine and Health Sciences. He earned his MD from Georgetown University School of Medicine. Professor Restak also maintains an active private practice in neurology and neuropsychiatry in Washington, D.C.