The Mirror neuron is perhaps the most fascinating neuron, allowing us to touch other brains, establishing a connection beyond words.
Before diving into the multiverse of mirror neurons we need to clear up some central concepts and provide a background. Mirror neurons were discovered in a landmark study where specific neurons in the brain of monkeys were discovered to become activated both when they carried out specific actions but also when observing someone else carryout those actions (1). Mirror neurons have since then been shown to be involved in autism, development of language and empathy. It has even been speculated that they have enabled humankind to cheat evolution jumping generations further in development then should be possible by pure Darwinism.
We all have and use the ability to ‘mind read’ on a daily basis. Mind reading is underpinned by two simple concepts which explain the principles of mirror neuron workings: theory-theory (TT) and simulation theory (ST). Theory- theory put very simply is a scientific method to deduce the underlying motives/behaviour behind someone’s actions (2). This is like an algebraic equation where x, the underlying reasoning for actions, is deduced using the information available to us. Simulation theory however involves placing yourself in someone else’s shoes and coming to a solution to a problem as that person would.
These two forms of mind reading can be understood in a thought experiment. Kahneman and Tversky (3) asked one cohort of individuals to imagine being in the place of someone who had missed their flight by 5 min. They also were asked to visualise being a second person in the same situation but the plane in this scenario departed at the correct time. Which individual do you think was more distressed in these two scenarios? It was striking that 97% thought that the first individual would be the most distressed. Theoretically, this is because of a common mechanism deployed by our brains to come to the same verdict. This involves using existing mechanisms in the mind to imitate and therefore predict what mental processes are occurring in another individual’s brain. We can already appreciate how these neurons enable empathy and even survival. On the other hand, simulation theory would reach the same conclusion, but this mechanism is based on the person putting themselves in the other person’s situation, thereby showing we all, for the most part, react to situations in a very similar way.
It is important to note that mirror neurons alone cannot decipher the difference between observing an action vs carrying out an action. To a motor neurone these both equally result in their activation. (This concept is described eloquently and simply by V.S Ramachandran on the impact theory podcast for those interested in further exploration.)
We can further explore this concept with a more interesting scenario. Synthesias are connections within the brain that lead to different senses being triggered synonymously (4). An example would be seeing colour when hearing sounds. Mirror touch synthesia is an example of a malfunction of mirror neurone functioning that results in a tactile sensation being elicited by observing another person being touched. It has been purposed that abnormally higher levels of activation of mirror neurons to be the culprit of this condition. Mirror neurons therefore in normal circumstances allow us to feel empathy when their actions are regulated in the context of the multitude of other signals entering the brain. An experiment on lovers shows the activation of mirror neurons in response to pain - a shock to a female subject and her partner (5). The response showed a remarkably similar activation of the pain response in the brain of the female being shocked and observing her partner being shocked, which shows that the ability to empathise is deeply rooted into us by mirror neurons. It is important to note that the shock used didn’t cause significant pain.
Perhaps mirror neurons can explain our empathy. By evoking similar neuron firing patterns to the observations we see, mirror neurons reflect the internal brain state of those external to us - allowing us to truly read minds.
Looking at wider evolution V.S Ramachandran proposes that a refinement in mirror neurone function in our ancestral history enabled humans to make dramatic advances in evolution (6). This conceptually makes a lot of sense. Imagine you are part of a tribe and its the monsoon season. It would be very difficult to survive very long hiding under trees and not knowing where to find food. Additionally, it would take an extremely long time, many generations, to develop adaptations to deal successfully with the monsoon season. We can however learn through mirror neurons via the aforementioned TT and ST theories, understanding why individuals are carrying out activities giving us the reasoning to do the same. We can learn how to build huts by observing how other members of our clan do this and we can also learn from other members where food can be found. Furthermore, we can ‘mind read’ as mentioned previously by observing facial expressions and observing other’s actions to determine if they are going to reveal themselves as a foe. It is absolutely fascinating that all these steps are facilitated by mirror neurons which clearly exhibits their significance to survival. It should be mentioned that this is a theory and other mechanisms too will be at play.
To finish of mirror neurons are essential in establishing social ties and is absolutely important in its functioning in everyday activities. Where function is disrupted this can manifest as autism. Following from the aforementioned theory- theory model, a child with Autism spectrum disorder ASD will be unable to deduce mental states due to the lack of activity of the mirror neurons. The attributes of determining mental states develop at an early stage. Mirror neurons are one of many factors that inform how we behave socially, and this is clearly relevant to ‘mind reading’ via TT. Children with ASD are unable to develop this social awareness and therefore don’t understand why people behave the way they do- they so lack social communication skills such as maintaining eye contact and recognising social cues. It should be noted that autism is a very complex condition and there are multiple facets to its development though recognising its association to broken mirror neurons helps with treatment. This entails increased engagement with children at an earlier stage of development that can help buffer against the lacking functionality of their mirror neurons so that they grow to have some social awareness. This discovery is very important as we can help such autistic individuals in their personal and professional development through targeted therapy (7).
In conclusion mirror neurons only exist because humans have evolved as social animals, this has resulted in common mechanisms in all brains to establish a human connection. Mirror neurons have stood the test of time and evolution revealing that social attributes of humans are not only nice to have but have been absolutely necessary to our survival. In light of this information, and given the times, it is interesting to appreciate how social interactions have been so intrinsic in a plethora of circumstances that effect all of us.
1) Winerman, L. The mind's mirror. Monitor on Psychology, 36(9). (2005, October).
2) Ratcliffe, M. "Folk Psychology is not folk psychology". Phenomenology and the Cognitive Sciences. 5 (1): 31–52. (2006).
3) Kahneman, D. and Tversky, A. The simulation heuristic, in Judgment Under Uncertainty (Kahneman, D., Slovic, P. and Tversky, A.,eds), pp. 201–208, Cambridge University Press (1982)
4) Globally Altered Structural Brain Network Topology in Grapheme-Color Synesthesia, Jürgen Hänggi, Diana Wotruba, Lutz Jäncke, Journal of Neuroscience 13, 31 (15) 5816 5828; (April 2011)
5) Linkovski O, Katzin N, Salti M. Mirror Neurons and Mirror-Touch Synesthesia. The Neuroscientist.23(2):103-108. (2017)
6) Edge (Internet), V.S. Ramachandran. MIRROR NEURONS and imitation learning as the driving force behind "the great leap forward" in human evolution. [6.1.2000] (cited 08/02/2021) Available from: https://www.edge.org/3rd_culture/ramachandran/ramachandran_index.html
7) Khalil R, Tindle R, Boraud T, Moustafa AA, Karim AA. Social decision making in autism: On the impact of mirror neurons, motor control, and imitative behaviors. CNS Neurosci Ther.24(8):669-676. (2018 Aug).