Why Do I Confuse Left and Right?
Scientific insights into the annoying everyday problem of left-right confusion.
Posted Mar 09, 2019
Left, right, what?
Almost anyone who has ever gone to a yoga class knows the situation: Everyone eagerly follows the instructions of the yoga teacher, but in the end, there are usually one or two people in class who stretch out the opposite arm or leg than everyone else — and this has been me more than once!
Left-right confusion is actually quite frequent in everyday life and happens to lots of people whenever a task requires them to differentiate between the two sides, and particularly under time pressure, such as when giving someone directions to turn left or right while sitting in the passenger seat of a fast-moving car.
So why do we confuse left and right all the time, but we have absolutely no problem distinguishing up from down or front from back? It turns out there might be two reasons for this.
On the one hand, differentiating between left and right is more complicated than differentiating between up and down, as what is left and what is right changes depending on the vantage point. Most of the time, we distinguish left and right from our own perspective, but if we have to distinguish them from the perspective of a person facing us, the side of our left arm is the side of their right arm — confusing, isn’t it?
On the other hand, differentiating between left and right is more complicated than differentiating between up and down, as the distinction is completely arbitrary, and there are no physical laws underlying it. You want to know what is up and what is down? Pick up an apple, and then drop it. Where it lands is usually down. Left and right? Not so easy.
How many people confuse left and right more or less regularly?
A surprising number of people experience issues with telling left from right in their daily lives, so if this ever happens to you, you are in good company. The first large study on the topic was published in the 1970s and investigated a sample of doctors and their spouses (Wolf, 1973). The result? About 9 percent of men and 17 percent of women stated that they frequently experienced left-right confusion in their daily lives. Some more recent studies estimate the numbers to be even higher. For example, an Australian study from 1990 found that about one-third of people at least sometimes experienced frustration with everyday situations that involve the discrimination of left and right (McMonnies, 1990).
Isn’t left-right confusion mostly harmless? Why do scientists need to research it?
While most left-right confusions in everyday life are harmless, there are certain jobs in which you really do not want to confuse left and right — surgeon probably comes to mind first. Disturbingly, left-right confusions in a medical setting still happen more often than one might think. For example, in January 2000, two doctors at a hospital in South Wales accidentally removed the functioning left kidney instead of the right kidney, which eventually led to the patient’s death (Dyer, 2004).
While left-right differentiation in itself is not necessarily a complicated task, medical professionals are often under enormous time pressure, which could enhance the chance of left-right confusions and other errors. Indeed, medical students often report insecurities in telling left from right (Gormley et al., 2019).
Therefore, it has been advised to use side marking before surgery, identifying clearly for the surgeon whether the left or the right limb or organ should be removed. The importance of this measure was revealed in a 2014 study of eye surgeons from Israel (Pikkel et al., 2014).
In this study, surgeons were asked to recognize the side of the operation by the patient’s name and by looking at the patient’s face from a 2-meter distance. Surgeons were able to correctly identify the side of the eye that was to be operated on in only 73 percent of cases based on the patient’s name, and in 83 percent of cases by looking at the patient’s face. The number of errors increased the longer the time between pre-operative examination and surgery was. Thus, if the doctors had indeed performed the surgery without the information from side markings on the patients, the probability for surgery on the wrong eye, at least in a few patients, was quite high.
What happens in the brain when we confuse left and right?
So why do we confuse left and right? Patient studies have shown that in particular the angular gyrus in the parietal lobe of the brain is highly important for discriminating between left and right. Damage in this brain area can lead to the so-called Gerstmann Syndrome (Gold et al., 1995), a rare neurological condition in which patients show four key syndromes:
- Finger agnosia (inability to name or distinguish the fingers)
- Agraphia (inability to write)
- Acalculia (difficulties in performing even simple mathematical tasks)
- Right-left confusion
Neuroscientists have used different techniques to investigate whether the angular gyrus also affects left-right confusion in healthy people and not only in patients with Gerstmann syndrome. For example, a group of scientists from the University of Durham in the UK used a technique called repetitive transcranial magnetic stimulation (rTMS) to investigate the role of the angular gyrus for left-right confusion (Hirnstein et al., 2011). rTMS uses a magnetic coil to induce a small electric current that stimulates specific brain areas which can either inhibit or excite their function. The researchers found that after rTMS of the left angular gyrus, participants performed worse in left-right discrimination than in a control condition without rTMS. Thus, disturbing the proper functioning of this brain area leads to more left-right confusion.
Some years later, a group of Norwegian scientists used a technique called functional magnetic resonance imaging (fMRI) to investigate left-right discrimination (Hjelmervik et al., 2015). fMRI uses magnetic resonance to identify brain areas that are active and therefore receive lots of oxygen from the blood during a given task. Participants had to lay in an fMRI scanner in a hospital and were looking at pictures of hands that pointed in various directions. Their task was to identify whether a hand was a left or a right hand. Analysis of the data revealed that there was indeed activation in the right angular gyrus and surrounding regions in the parietal lobe during this left-right discrimination task.
So what does the angular gyrus actually do? A lot, it turns out. Studies have shown that it is involved in language-related processes, like sematic processing and word reading, but also in memory and spatial cognition (Seghier, 2013). It seems to work like a cross-modal hub that integrates these different processes to guide our actions. This also explains why it is so relevant for left-right confusion: Differentiating left and right requires verbal processes (the words left and right need to be applied to objects in the environment), memory (you have to remember which is left, and which is right), and spatial processing (you have to process whether objects around you are on the left or the right side). If the integration of these different processes fails, left-right confusion might happen.
What can I do to protect against left-right confusion?
Left-right confusion seems to happen more often when we are under stress or time pressure, so slowing down a bit is probably a good idea. Also, when you are in doubt as to which side is which, an old trick is to make an L shape with the thumb and the index finger of each hand. The one that actually looks like the letter L is the left hand.
Dyer O. (2004). Doctors suspended for removing wrong kidney. BMJ, 328, 246.
Gold M, Adair JC, Jacobs DH, Heilman KM. (1995). Right-left confusion in Gerstmann's syndrome: a model of body centered spatial orientation. Cortex, 31, 267-283.
Gormley GJ, Brennan C, Dempster M. (2019). 'What … you can't tell left from right?' Medical students' experiences in making laterality decisions. Med Educ, in press.
Hirnstein M, Bayer U, Ellison A, Hausmann M. (2011). TMS over the left angular gyrus impairs the ability to discriminate left from right. Neuropsychologia, 49, 29-33.
Hjelmervik H, Westerhausen R, Hirnstein M, Specht K, Hausmann M. (2015). The neural correlates of sex differences in left-right confusion. Neuroimage, 113, 196-206.
McMonnies, C.W. (1990). Left‐right discrimination in adults. Clinical and Experimental optometry, 73, 155-158.
Pikkel D, Sharabi-Nov A, Pikkel J. (2014). "It is the left eye, right?". Risk Manag Healthc Policy, 7, 77-80.
Seghier ML. (2013). The angular gyrus: multiple functions and multiple subdivisions. Neuroscientist, 19, 43-61.
Wolf SM. (1973). Difficulties in right-left discrimination in a normal population. Arch Neurol, 29, 128-129.