Left Brain vs Right Brain: Definition, Theory, & Differences

By Kelsey Schultz, Ph.D. Candidate
​Reviewed by Tchiki Davis, M.A., Ph.D.
Our left brain and right brain perform different functions, but not in the way you might think. Keep reading to learn the truth about the left and right sides of the brain.
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You’re likely familiar with the idea that the left side of the brain performs different functions than the right side. A person who excels in logic and reasoning might be categorized as left-brained, and a creative, artistic person would be described as right-brained. Though it is true that there are some functions specific to each half of the brain, the left-brained/right-brained dichotomy as popularly understood is a mischaracterization. Let’s talk more about what science has to say when it comes to the differences between the left brain and the right brain.
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What Is Left Brain vs Right Brain? (A Definition)

The left brain and right brain refer to each of the two halves of the brain, also known as hemispheres. The two hemispheres are connected by a structure called the corpus callosum, which allows them to communicate with one another. While each hemisphere is nearly a mirror image of the other, they aren’t exactly the same. This is called hemispheric asymmetry. Part of hemispheric asymmetry includes different functions. That is, there are some functions that one hemisphere specializes in more than the other hemisphere.   
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The common understanding is that this hemispheric specialization is manifested in personality differences. For example, The American Heritage Dictionary (2008) defines left-brained and right-brained in the following way:

  • Left-brained adj: 1. Having the left brain dominant. 2. Of or relating to the thought processes, such as logic and calculation, generally associated with the left brain. 3. Of or relating to a person whose behavior is dominated by logic, analytical thinking and verbal communication, rather than emotion and creativity.
  • Right-brained adj: 1. Having the right brain dominant. 2. Of or relating to the thought processes involved in creativity and imagination, generally associated with the right brain. 3. Of or relating to a person whose behavior is dominated by emotion, creativity, intuition, nonverbal communication, and global reasoning rather than logic and analysis.
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While it is true that the two hemispheres of the brain do have some specialized functions, there is little evidence to support the popular understanding of hemispheric specialization. In reality, both hemispheres are highly interconnected, with different regions constantly communicating with one another and working together to carry out most cognitive tasks.

Left Brain vs Right Brain Theory

The theory of hemispheric specialization - or the idea that the left and right side of the brain performs different functions - has been around for a long time. The observation that most humans prefer to use their right over their left hand was one of the first clues.
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In the 1800’s a French physician named Pierre Paul Broca made a discovery that provided evidence that some brain functions are localized to distinct brain areas. Specifically, he found that people with damage to a particular region in the lower frontal cortex on the left side of the brain struggled to produce speech (Broca, 1863).

In the following century, substantial evidence supporting the localization of brain function has been accumulated. Some of the most compelling evidence came from studies involving patients who had their corpus callosum (the structure that connects the two hemispheres) severed. This aptly-named split-brain procedure was a clinical method for controlling epilepsy but also had the result of allowing researchers to study the functions of each hemisphere independently. We’ll get into more details about split-brain studies a little later on, but for now, it is just important to know that this research provided evidence supporting the theory that the left hemisphere was important for language and the right hemisphere was important for emotional and non-verbal functions (Corballis, 2014).

These and similar findings led to the extrapolation that the left hemisphere was responsible for logic and critical thinking and the right hemisphere was responsible for emotion and creativity (Corballis, 2014).

Is Left Brain vs Right Brain a Myth

As we now know, the idea that each hemisphere has specialized functions is valid. Interestingly, hemispheric functional asymmetry is something that is seen in all vertebrate species (Herve, et al., 2013). For example, about two-thirds of chimpanzees appear to be right-handed (Meguerditchian et al., 2010). However, the way that left-brain and right-brain behaviors are typically described in popular media tends to be oversimplified and exaggerated (Corballis, 2014).

Differences Between Left Brain and Right Brain

As mentioned earlier, the two hemispheres are nearly mirror images of each other, but there are some structural differences that are typically found. Below are a few examples of anatomical asymmetries in the brain (Kang, et al., 2015).
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  • Hippocampus: The hippocampus, a subcortical structure that is critical for memory formation, is commonly larger on the left.
  • Heschl's gyrus: Heschl's gyrus, which is a region of the brain involved in processing auditory information, is larger in the left hemisphere in most people.
  • Anterior Cingulate Cortex: The anterior cingulate cortex is thought to be involved in a number of processes including pain perception, emotion regulation, and cognitive control. This region is commonly larger in the right hemisphere. 
  • Planum temporale: The planum temporale, which is a region of the brain involved in processing language, is also larger in the left hemisphere in most people.

In addition to the anatomical differences between the left and right sides of the brain, there is also evidence that supports functional differences including language, visuospatial skills, and attention. 

Left Brain vs Right Brain Research
Some of this evidence comes from the split-brain research mentioned earlier. This research takes advantage of the fact that the left half of your visual field is processed in the right hemisphere and the right half of your visual field is processed in your left hemisphere. Thus, in split-brain patients who lack the corpus callosum, which unites the two hemispheres, it is possible to show something to one hemisphere of the brain without the other hemisphere knowing about it. That is, when some kind of stimulus is located strictly in the left visual field and not the right, the left hemisphere doesn’t have access to that information.

Much split-brain research - especially the early studies pioneered by Roger Sperry, Michael Gazzaniga, and Joseph Bogen in the 1960s - involved presenting patients with an image that was only visible in one-half of their visual field. The patient would then be asked to point to the picture and describe what it was. 

When presented in the right half of the visual field (so only the left hemisphere has access to it) patients were able to point to the image with their right hand and were able to describe what it was. When the image was presented in the left half of the visual field (to the right hemisphere), patients were able to point to the image with their left hand but would state that they didn’t see any image (Gazzaniga, 1962; Sperry, 1968). The observation that patients were unable to say what they saw when an image was presented to the right hemisphere but were able to when the image was presented to the left hemisphere was further evidence that language is a product of the left hemisphere.

Studies using this same methodology also demonstrated that the right hemisphere is better at visual-spatial judgments. For example, one study asked split-brain patients to perform a task in which they were shown two simple images of shapes in one half of their visual field. The second image was either identical to the first or varied in a spatial dimension (size, orientation, location) or a non-spatial dimension (brightness; Corballis et al., 2001).

The researchers found that both hemispheres were able to determine whether the two images were the same brightness or not, but the right hemisphere was significantly better at spatial judgments than the left hemisphere.

Left Brain vs Right Brain and Language

As we now know, the left brain is the master of language. The discovery of the importance of the left hemisphere for language is typically attributed to Paul Broca, who found that people with damage to a frontal region in the left hemisphere had the same speech deficits. These speech deficits, now known as Broca’s aphasia, include the following symptoms (Acharya & Wroten, 2017):
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  • The poor or absent grammatical structure of sentences
  • Difficulty forming complete sentences
  • The tendency to omit prepositions, small linking words, and conjunctions
  • Difficulty using verbs
  • Impaired ability to repeat phrases
  • Difficulty with reading and writing

A contemporary of Broca’s, Carl Wernicke, also discovered a region in the left hemisphere that was important for a different aspect of language, now known as Wernicke’s area. Whereas Broca’s area is largely important for speech production or expression, Wernicke’s area is important for speech comprehension. Damage to this area causes a language deficit called Wernicke’s aphasia. People with this deficit are able to speak just fine, but the content of their speech is difficult to understand and can sometimes be unintelligible. Interestingly, unlike Broca’s aphasia, people with Wernicke’s aphasia are not aware of their deficits (Acharya & Wroten, 2022).

Left Brain vs Right Brain and Thinking

Although we’ve talked quite a bit about hemispheric asymmetry and the localization of some functions to one hemisphere or the other, it is important to remember that, in general, both hemispheres are important for the vast majority of cognitive functions. Thinking and reasoning are two examples of functions that are typically associated with the left brain, but these require communication between many regions of the brain on both sides.

Left Brain vs Right Brain and Learning Styles

Learning styles refer to the different ways in which people prefer to learn and process information. There are various models of learning styles, but the most common ones include:

Visual learners​
These individuals prefer to learn by seeing and observing. They tend to prefer visual aids such as diagrams, graphs, and videos.

Auditory learners
These individuals learn best through listening and hearing. They tend to prefer lectures, discussions, and podcasts.

Kinesthetic learners
These individuals prefer to learn through physical activity and hands-on experiences. They tend to prefer activities such as experiments, role-plays, and games.

Reading/writing learners
These individuals prefer to learn through reading and writing. They tend to prefer textbooks, notes, and written instructions.

Although people commonly prefer some learning styles over others, there isn’t great evidence to support the idea that processing information in the modality of your preferred learning style will actually improve educational outcomes (Pashler et al., 2008). 
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Learning style preference, however, may be influenced by the personality characteristics that are ascribed to left-brain vs right-brain dominance. For example, a “left-brained” person might prefer to learn by reading and writing whereas a “right-brained” person might prefer visual aids.

Left Brain vs Right Brain and Art

The connection between the right brain and art is thought to have arisen from its dominance in visual-spatial processing. The logic is that art and creativity rely on this kind of processing and because the right hemisphere is the major player the right hemisphere must be the artistic side (Corballis, 2014). 
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This isn’t necessarily a wild leap in logic, but it is an extrapolation that hasn’t found much support. In fact, imaging research shows the involvement of both hemispheres in creative processes (Ellamil et al., 2012). Other studies have shown that creativity is actually associated with less lateralization (Lindell, 2011). That is, greater creativity is associated with more communication between the two hemispheres rather than more activity in the right hemisphere.

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Final Thoughts on Left Brain vs Right Brain

The distinction between left brain functions and right brain functions isn’t necessarily wrong. There are some functions, such as language and visual-spatial processing, that tend to be predominantly produced by one hemisphere or the other. However, the common understanding of the left brain vs right brain is an exaggeration and oversimplification of hemispheric asymmetry. Nevertheless, thinking of yourself as left-brained or right-brained, or categorizing activities as engaging your left brain or your right brain may still be useful as a descriptive tool, regardless of its literal accuracy. For more about the left brain vs right brain, check out this excellent video from TED-ed:

Video: The left brain vs. right brain myth

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