Left-brained or right-brained? What brain research actually shows about personality

You may have heard someone say, “I’m right-brained, so I go with my feelings; my friend is left-brained, so they’re logical.” In this picture a left-brained person is logical and methodical, and a right-brained person is creative and intuitive. The authors of a 2013 brain imaging study summed up how popular reports use “left-brained” and “right-brained” for both personality traits and ways of thinking (Nielsen et al., 2013).

The short answer is that the two halves of the brain do divide some of the work. In most people language relies mainly on the left hemisphere, while paying attention to the world around us and recognising faces lean on the right (Corballis, 2014; Badzakova-Trajkov et al., 2010). But a study that analysed brain scans of 1,011 people aged 7 to 29 concluded that these left–right differences are a local property of particular networks, and that the data do not fit the idea of “left-brained” or “right-brained” people whose whole brain leans one way (Nielsen et al., 2013).

That study had no measures of the participants’ personality (Nielsen et al., 2013), so it did not test the link with personality itself. What the studies in this guide show is closer to this: they give no grounds for sorting people into two types, left-brained and right-brained. mind.io has no left-brain/right-brain test. If you want to see your personality traits as scores, you can take the Big Five test or the MBTI test.

This guide covers what really differs between the hemispheres, how the idea spread from split-brain research, what the study of 1,011 brains found, common beliefs about creativity, logic and left-handedness, why so many people believe it, and how to read a left-brain/right-brain quiz. It is not meant to make fun of anyone who enjoys such quizzes.

Differences between the hemispheres are real. The best-known example is language: an estimated 95–99% of right-handers and about 70% of left-handers rely mainly on the left hemisphere for language (Corballis, 2014). In a study that measured brain blood flow with ultrasound while 326 healthy people thought of words, the share whose language was mainly on the right rose with left-handedness: 4% of strong right-handers, 15% of ambidextrous people and 27% of strong left-handers (from the abstract; Knecht et al., 2000).

A French study that deliberately recruited many left-handers (153 of 297 participants) found clear right-hemisphere dominance for producing sentences in only about 7% of the left-handers. Assuming 10% of people are left-handed, the authors estimated that such people make up less than 1% of the general population (Mazoyer et al., 2014).

Other tasks lean right. In a New Zealand fMRI study of 155 people, with left-handers over-represented (48), watching facial expressions, a task only 86 of them did, was right-dominant in 50 of 53 right-handers (94.3%) and 24 of 33 left-handers (72.7%), and a spatial attention task (judging whether a line is cut exactly in the middle) was right-dominant in 79.4% and 78.7% (Badzakova-Trajkov et al., 2010). In the study of 1,011 people, the right-lateralised hubs belonged to networks for attending to the outside world, and the authors pointed to lesion studies in which neglect of one side of space is much more common after right-hemisphere injury (Nielsen et al., 2013).

These differences do not move together like a single switch that makes one side dominant overall. In the same New Zealand study, there was some complementary relation (the more strongly language leaned left, the more the face and spatial tasks leaned right), but handedness scores and the left–right bias on the spatial task were essentially uncorrelated (r = .001), and while most people showed the typical pattern of language on the left and faces and space on the right, a few showed the full reverse and others had both kinds of task on the same side (Badzakova-Trajkov et al., 2010). A study of 300 adults at rest reported that brain asymmetries fall into four independent factors linked to language, vision, internal thought and attention (from the abstract; Liu et al., 2009; Corballis, 2014).

Nor do the hemispheres work alone. They are joined by hundreds of millions of nerve fibres, so each is constantly informed about what is happening in the other (Nobel Assembly, 1981), and Roger Sperry, who won a Nobel Prize for split-brain research, said that in the normal state the two hemispheres appear to work closely together as a unit, rather than one being turned on while the other idles (Sperry, 1981). Surveys of teachers’ brain knowledge score “the left and right hemispheres work together” as a correct statement (Dekker et al., 2012; Macdonald et al., 2017).

Interest in the two sides of the brain grew in the 1860s, when speech was found to depend mainly on the left hemisphere. Because the left hemisphere also controls the right hand, it came to be called the dominant or major hemisphere, and the right one the minor hemisphere (Corballis, 2014).

Modern split-brain research began in the 1960s. Reports on split-brain patients go back to the 1940s, and Sperry had been doing animal experiments since the early 1950s (de Haan et al., 2020; Nobel Assembly, 1981); in the 1960s, Roger Sperry, Joseph Bogen and Michael Gazzaniga began studying patients whose corpus callosum, the bundle of fibres joining the hemispheres, had been cut as a last resort against severe epilepsy that other treatment could not control (from the abstract; Gazzaniga, 2005; Sperry, 1981). Tests that showed information to one hemisphere at a time revealed that the right hemisphere, though largely unable to speak, was good at reading faces, fitting designs into larger patterns and perceiving wholes from their parts (Sperry, 1981). In 1981 Sperry received the Nobel Prize in Physiology or Medicine “for his discoveries concerning the functional specialization of the cerebral hemispheres” (Nobel Assembly, 1981).

The split-brain patients were a relatively small group. After surgery they were reported to behave in a socially ordinary way and to feel unchanged, although their behaviour outside experiments has not been observed in great detail, and the full operation is rare today (de Haan et al., 2020). Sperry wrote that after recovery such a person would as a rule go unnoticed in a first conversation or even a routine medical examination (Sperry, 1981).

As the findings reached the public, the idea grew. The 1981 Nobel press release said that the Russian physiologist Ivan Pavlov had divided humankind into thinkers and artists, and added: “Perhaps the left hemisphere is the dominant one in thinkers and the right hemisphere in artists” (Nobel Assembly, 1981). That line comes from the press release issued by the Nobel Assembly at Karolinska Institutet, not from Sperry himself. In his Nobel lecture the same year, Sperry presented research, notably by Jerre Levy, suggesting that the two hemispheres use different cognitive modes, yet said that some of the conclusions, along with the “growing wave of semipopular extrapolations” about the left brain and the right brain, called for caution, and described the left–right dichotomy as “an idea with which it is very easy to run wild” (Sperry, 1981).

Similar readings kept coming. The neuroscientist Michael Corballis judged most of the speculation that followed split-brain research to be exaggerated or ill-founded, and named Betty Edwards’s drawing book Drawing on the Right Side of the Brain, first published in 1979, as the classic example of the popular view that creativity comes from the right hemisphere (Corballis, 2014). Another review noted the many popular books offering a right-hemisphere solution to topics from drawing to money management (from the abstract; Lindell, 2011). Japanese researchers recorded their impression that the so-called “right-brain boom” Japan saw in the 1970s and 1980s was making a comeback (Hatta et al., 2010).

If there were left-brained and right-brained people, some people’s left-hemisphere connections would be stronger across the board, and others’ right-hemisphere connections would be. A team at the University of Utah set out to test this directly with publicly shared resting-state brain scans (fMRI) of 1,011 people aged 7 to 29, collected by research sites in several countries, among them Beijing in China, Oulu in Finland, Leiden in the Netherlands and New York in the US. They divided the grey matter into 7,266 regions and measured how far each connection leaned to one side by comparing connection strengths before and after flipping the images left to right (Nielsen et al., 2013).

They found 9 left-lateralised hubs, centres of many lateralised connections, and 11 right-lateralised hubs. The left hubs included language areas such as Broca’s and Wernicke’s areas, and parts of the default mode network, which is more active at rest and is thought to be involved in attending to inner experience; the right hubs belonged mostly to networks for attending to the outside world (Nielsen et al., 2013). In other words, networks that lean left or right do exist.

The key question came next: in a given person, do the left-leaning connections get stronger together? The connections that varied together were almost all ones that shared a hub (141 of 144 on the left, 314 of 329 on the right). Between left-hub and right-hub connections, only 20 of 1,620 comparisons (1.2%) showed a significant negative relationship and 16 (1.0%) a positive one. The authors concluded that lateralisation is a local rather than a whole-brain property, and that “an individual brain is not ‘left-brained’ or ‘right-brained’ as a global property” (Nielsen et al., 2013).

The study has limits. As the authors themselves state, the data included no behavioural or personality measures, and handedness information was lacking; the study measured only the strength of connections, not what information they carry, and the participants were aged 7 to 29 (Nielsen et al., 2013). So it is best read not as showing that personality is unrelated to the brain, but as a direct test of the premise behind left-brained and right-brained types, namely that some people’s whole brain leans one way, and that premise did not hold. One study does not settle everything, but it points the same way as the New Zealand study, where most people showed the typical pattern yet the lateralisation of different functions was to some degree independent (Badzakova-Trajkov et al., 2010).

Creativity and the right hemisphere is a topic on which studies disagree. A 2010 meta-analysis of studies of brain activity during creative thinking concluded that the right hemisphere is relatively more dominant (from the abstract; Mihov et al., 2010). A 2013 meta-analysis of 34 imaging studies, by contrast, reported that the regions shared by various creativity tasks were mainly in the left hemisphere (from the abstract; Gonen-Yaacovi et al., 2013). And a 2010 review of 72 experiments concluded that creative thinking does not depend critically on any single brain region and is “not especially associated with right brains” (from the abstract; Dietrich & Kanso, 2010).

Another review found that the research it covered indicates greater right-hemisphere activity during creative tasks, but added that the interaction of many distant regions across both hemispheres is also a crucial part of creativity, concluding that creativity is better seen as a distributed than as a purely lateralised function (Lindell, 2011). More recent work focuses on large brain networks that can work against each other cooperating during creative thought (from the abstract; Beaty et al., 2016). Above all, these studies looked at brain activity during tasks; none of them showed that creative people are “right-brained”.

“Logic on the left, emotion on the right” is also too simple. The authors of the study of 1,011 people suggested that a schema more consistent with their results than logic versus creativity would link left-leaning connections with language and the perception of internal stimuli, and right-leaning ones with attention to the outside world (Nielsen et al., 2013). Some research does report a right-hemisphere bias for emotion: Corballis notes that a right-hemisphere dominance for emotion seems to be present in all primates studied so far (Corballis, 2014), and the New Zealand researchers describe right-hemisphere dominance for some nonverbal functions “such as spatial or emotional processing” (Badzakova-Trajkov et al., 2010). But Sperry observed that even in split-brain patients, emotional reactions arising on one side spread rapidly to both hemispheres, apparently through the undivided brain stem, and wrote that, unlike other cognitive functions, emotions “have never been readily confinable to one hemisphere” (Sperry, 1981). Emotion cannot simply be called the right hemisphere’s job.

Another common claim is that training the right brain builds creativity. When 485 Japanese university students were asked in 2010, 75.9% judged this statement correct, though the researchers surveyed it as an example of a scientifically false belief (Hatta et al., 2010). The statement that short bouts of coordination exercises can improve the integration of left and right hemisphere function was also classed as a neuromyth in a teacher survey, where 88% of the UK teachers and 82% of the Dutch teachers judged it correct (Dekker et al., 2012). None of the studies covered in this guide showed that training one hemisphere on its own makes people more creative.

Left-brained and right-brained types are a widespread idea in education too. In a survey of 137 teachers in the Dorset region of the UK and 105 teachers around Amsterdam in the Netherlands, 91% of the UK teachers and 86% of the Dutch teachers judged correct the statement that “differences in hemispheric dominance (left brain, right brain) can help explain individual differences amongst learners”. These were teachers who chose to take part out of an interest in the brain and learning (Dekker et al., 2012).

In a US online study of 3,877 people, the statement that some of us are “left-brained” and some are “right-brained”, and that this helps explain differences in learning, was judged true by 64% of the general participants, 49% of educators and 32% of people who had taken many neuroscience courses. All were volunteers with at least some college education, and the authors themselves noted that calling them the “general public” may be misleading (Macdonald et al., 2017).

Surveys in Korea and Japan also found the belief widespread (the groups and questions differ, so the figures cannot be compared directly). In a survey of 521 Korean pre-service teachers (269 elementary and 252 secondary education students), fewer than 10% answered the item about left-brained and right-brained students correctly (from the abstract; Park et al., 2016). According to a table in a later paper that cites that study, 94% of the Korean pre-service teachers agreed that differences in hemispheric dominance help explain individual differences among learners (Park et al., 2016, as cited in Chu, 2017). In a 2010 survey of 485 Japanese university students, 89.5% judged “there are left-brain types and right-brain types of people” correct, the highest share of the 20 statements (Hatta et al., 2010).

Why is it so widely believed? For one thing, it is not made up from nothing: it partly stems from real findings that some functions, such as language, lean to one hemisphere (Macdonald et al., 2017). Statements people had heard often were also more likely to be judged correct (Hatta et al., 2010). In one teacher survey, those with more general knowledge of the brain actually believed more neuromyths (Dekker et al., 2012), and in another study the group who had taken many neuroscience courses believed it less often (32%), but the belief had not disappeared (Macdonald et al., 2017). Japanese students who had heard in a lecture that the left-brain/right-brain split has no scientific basis rated the statement less correct than students at another university who had not (3.27 versus 3.82 on a five-point scale), but this compared different students, not the same students before and after the lecture, and the authors noted that the course was an elective that already interested students may have chosen (Hatta et al., 2010).

A two-type description is easy to remember, and when a result is made of sentences that fit almost anyone, it can feel like it is about you; the Barnum effect guide covers this in detail. Since teachers and university-educated adults believe it too, there is nothing embarrassing about having believed it. For how other systems such as blood types and zodiac signs compare, see MBTI, blood types, zodiac signs and saju. The related classroom idea that each person has a separate strongest intelligence is examined in the multiple intelligences guide.

A widely shared “left-brain/right-brain test” online is the spinning dancer, the silhouette of a woman turning on one foot. Published online in 2003 by the Japanese Flash designer Nobuyuki Kayahara, it is an illusion that can be seen turning either clockwise or anticlockwise. Canadian researchers looked into it after it spread as a “test” to distinguish “right-brainers” from “left-brainers” (Troje & McAdam, 2010).

In a 2008 online poll that the researchers cite, about two thirds of some 1,600 respondents saw it turning clockwise. The researchers explained this bias not by brain type but by the visual system’s preference for interpreting objects as seen from above rather than from below. They also re-created a silhouette like the original in 12 versions, varying the camera height (3 or 10 degrees above or below) and the rotation speed, and showed each version once, for four minutes, to each of 24 people: the direction they saw flipped 3.68 times a minute on average, and across these evenly mixed camera angles they saw it turning clockwise 50.8% of the time (Troje & McAdam, 2010). Since the direction keeps flipping even for the same person, the first direction you see cannot sort brains into types.

There are also quizzes that read your brain type from which thumb ends up on top when you clasp your hands, or which arm is on top when you fold them. The two studies of these postures covered here looked only at their link with handedness, and even that is inconsistent: one study found hand clasping, arm folding and handedness to be independent of one another (from the abstract; Ogah et al., 2012), while a study of two large Central European samples (7,658 and 5,062 people) reported links with handedness (from the abstract; Tran et al., 2014). Neither measured brain type or personality.

Left-brain/right-brain questions that ask whether you follow your gut or a plan record how you describe the way you think and work, not which hemisphere is more active. The company behind the Herrmann Brain Dominance Instrument (HBDI), a thinking-preference questionnaire built on a four-part map of the brain, itself says that the model is a metaphor for how we think, that the HBDI does not measure activity in specific areas of the brain, and that the model does not categorise people as right- or left-brained (Herrmann International website). Results like these can be enjoyed as a self-description and a conversation starter.

Whatever the quiz, try reading it this way. First, remember that the result sums up the preferences you reported; it is not a picture of your brain. Second, ask whether the sentences would fit a friend just as well; if many would fit anyone, the Barnum effect can make the result feel more accurate than it is. Third, if you want your traits as scores, try the Big Five test, which reports five traits, and if you would like to sum yourself up in a type, the MBTI test; its limits are covered in MBTI accuracy. These suggestions are drawn from the research in this guide rather than methods tested in studies.

Q. Are left-handed people right-brained? A. Not in that sense. Roughly one person in ten is left-handed: a meta-analysis put the best overall estimate at 10.6% (9.3% to 18.1% depending on the criterion) (from the abstract; Papadatou-Pastou et al., 2020). Yet about 70% of left-handers, like right-handers, rely mainly on the left hemisphere for language (Corballis, 2014). In a study of 662 young adults in New Zealand, left- and right-handers did not differ on any of the Big Five traits, though mixed-handers were more introverted than either group; in a second study in the same paper, both left- and right-handers believed that left-handers are more introverted and more open to experience (from the abstract; Grimshaw & Wilson, 2013).

Q. Does training the right brain boost creativity? A. We found no evidence that it does. Creative thinking is described as the work of many regions and networks across both hemispheres rather than of the right hemisphere alone (Lindell, 2011; Beaty et al., 2016), and “training the right brain builds creativity” was surveyed in a Japanese study as an example of a false belief (Hatta et al., 2010).

Q. If the spinning dancer turns clockwise for me, am I right-brained? A. No. The direction is biased by the visual system’s tendency to assume a view from above, and in the lab it flipped 3.68 times a minute on average for the same viewers (Troje & McAdam, 2010).

Q. My left-brain/right-brain quiz result fits me perfectly. A. A result made of sentences that fit almost anyone easily feels accurate (see the Barnum effect). These quizzes also sum up the thinking and working preferences you reported, so the result may describe your preferences well; that still does not show which hemisphere is dominant.

Q. So do the two hemispheres do the same things? A. No. In most people language leans to the left hemisphere, and face processing and spatial attention to the right (Corballis, 2014; Badzakova-Trajkov et al., 2010). What has no support is using these differences to sort whole people into left-brained and right-brained types (Nielsen et al., 2013).

Q. Do people who have had split-brain surgery act like two people? A. In the lab, when information is shown to one hemisphere only, the two hemispheres can respond separately, but in everyday life the patients were reported to get along in a socially ordinary way and to feel unchanged. Whether consciousness itself is split is still an open question among researchers (de Haan et al., 2020).

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