An important problem in psychological research is how to use findings from basic cognitive neuroscience to form an idea about what goes on in an individual. This step from cognitive experimental research to individual differences has been described as uncharted territory decades ago [1], and not enough intervening methodological work has been dedicated to working out how to connect the two fields. In fact, in recent years researchers have even concluded that these two areas of psychology, cognitive and differential, aim for different levels of explanation, examine different statistical features of the data, and that these differences in approach may be irreconcilable [2].
At the same time, interest in using cognitive experiments to find biomarkers has been growing. More research, more funding, and more general interest has been invested in this direction than in other areas of psychology, but with very little to show for it. Three decades of searching for mental health biomarkers has left us with a minefield of null results. Some interpret this to mean that we need better neural data or better statistical tools [3], others question whether it makes sense to think about mental health problems as disorders of the nervous system [4], while yet others question the accuracy of the diagnostic systems that we are mapping neural data onto [5]. All these points have merit. Here, I wanted to discuss a more basic problem, a misunderstanding that has to do with something as mundane as how we interpret t-tests.
In the clinical literature, for example, we might read about the notion of ‘right brain to right brain communication’. This refers to communication that is non-verbal, unconscious, and based around emotional signals [6]. The notion of such communication in uncontroversial, as we all continuously read subtle social cues from our surroundings and adapt to them without conscious effort. The idea that this is based on my right brain communicating with your right brain, however, rests on experiments that show that emotional stimuli lead to a bigger boost in the neural signal than non-emotional stimuli, and that this difference in boosts is more reliably observed in the right hemisphere than in the left [7]. In the clinical literature, this is sometimes assumed to mean that it is a general truth that emotions are processed in the right brain in all people, and that in any one person, information processing in the right brain will increase in the presence of more emotion. Neither of these conclusions follow from the findings.
To understand what a significant t-test implies, we can think about an intuitive fact that can also be t-tested: men are taller than women. We easily understand that this means that the statistical representation of the average man is taller than the statistical representation of the average woman. If we were to repeatedly draw random samples from the population, we would find that the average male height will almost always be larger than the average female height. But when we say that the right brain processes emotion more than the left brain, we lose sight of what the t-test means.
It does not mean that the right brain processes emotion while the left brain is dedicated to non-emotional material. That would be like concluding that, because men are taller than women, women don’t have height. Further, it does not mean that the right brain processes emotion more than the left brain in all people. That would be like concluding that all men are taller than all women. It does not mean that in any one person the right brain always processes emotion more than the left brain across all emotional compared to non-emotional situations. That would be similar to expecting that if we drew tiny male and female samples, consisting of a few people each, each mini-group of men will always have an advantage in height relative to the women. And it especially does not mean that the more emotional a situation is, the more my right brain will be active. That would be like expecting that the more a man engages in manly behaviour, the taller he gets. These all might be true statements about the left and right brain. They could be. But they do not follow from the data. They are leaps of faith.
Cognitive scientists are no better placed to unravel this mismatch between data and conclusions. In fact, it is part of their philosophical approach to assume that a difference between conditions reflects a general law, and that any observed variance between people is due to experimental error. In other words, everyone really shows this effect, but in some people we don’t observe it due to noise in the signal, which is why distributions tend to overlap. If we could extract a pure measure of emotions processing, they would no longer overlap. This is like understanding that height overlaps between men and women, but expecting that some biological measure of pure masculinity would always contain more genes for tallness than a biological measure of pure femininity. A leap of faith.
A cognitive experiment is suited to a statistical approach that involves means and variance, but a cognitive scientist applies a theoretical approach that interprets only the means. Brain lateralisation findings could easily be described in an entirely different way: of the 30 participants in the experiment, 18 showed stronger neural activation to emotional stimuli in the right hemisphere than in the left, 8 participants showed no effect of hemisphere, and 4 participants showed an effect in the opposite direction. Therefore, if we were to apply the same experiment to the next randomly selected individual, our confidence that their neural activity to emotional stimuli would be right-lateralised is about 60%. The statistical representation of entire sample taken together, shows evidence of right-lateralisation. The variance did not get lost in translation by the clinicians, it got dropped at the outset by the cognitive psychologists.
For the picker of nits aficionados, I will mention, just for fun, that visual attention is also known to be right-lateralised [8]. Attention is also known to increase the neural signal. Therefore, any difference between conditions might get a little boost on the right side, making the lateralised effect of attention appear like a lateralised effect of our chosen experimental factors, in this case emotion. But that’s not all. In some cases, objectively measured lateralisation does not stem from neural or cognitive effects at all. In auditory neuroscience, for example, responses to pure tones measured by magnetoencephalography tend to be right-lateralised due to a small but persistent asymmetry in cortical folding. This asymmetry means that we can measure the same neural signal a bit better when it’s on the right side than on the left, as we get a better view of the pyramidal neurons along Heschl’s gyrus [9]. Lateralisation is deliciously complicated.
In the end, the popularity of right-brain communication in the literature might stem from a need to prove that emotional attunement is somehow more real if it can be localised to a brain area. This, to my mind, is a sad consequence of a lack of scientific investment in the less biological aspects of what makes us tick. Leaps of faith are good, but only after a careful examination of the translation from statistical to theoretical concepts. Only then can we hope to translate findings from functioning in experiments to functioning in our day to day lives.
References
[1] Cronbach, L. J. (1957). The two disciplines of scientific psychology. American psychologist, 12(11), 671.
[2] Borsboom, D., Kievit, R. A., Cervone, D., & Hood, S. B. (2009). The two disciplines of scientific psychology, or: The disunity of psychology as a working hypothesis. Dynamic process methodology in the social and developmental sciences, 67-97.
[3] Woo, C. W., Chang, L. J., Lindquist, M. A., & Wager, T. D. (2017). Building better biomarkers: brain models in translational neuroimaging. Nature neuroscience, 20(3), 365-377.
[4] Johnstone, L., & Boyle, M. (2018). The power threat meaning framework: An alternative nondiagnostic conceptual system. Journal of Humanistic Psychology, 0022167818793289.
[5] Frances, A. (2013). One manual shouldn’t dictate US mental health research. New Scientist, 5.
[6] Schore, A. N. (2014). The right brain is dominant in psychotherapy. Psychotherapy, 51(3), 388.
[7] Silberman, E. K., & Weingartner, H. (1986). Hemispheric lateralization of functions related to emotion. Brain and cognition, 5(3), 322-353.
[8] Bartolomeo, P., & Malkinson, T. S. (2019). Hemispheric lateralization of attention processes in the human brain. Current opinion in psychology, 29, 90-96.
[9] Shaw, M. E., Hämäläinen, M. S., & Gutschalk, A. (2013). How anatomical asymmetry of human auditory cortex can lead to a rightward bias in auditory evoked fields. Neuroimage, 74, 22-29.
To cite this blog post, please use: Todorovic, Ana. "Problems in translation in right brain communication". Web blog post. NeuroAnaTody.com, published March 2023. Web.