Questioning the evidence

(The outline of McGilchrist’s thesis is here: https://jotsandscribbles.blog/2023/11/07/introduction-to-the-master-and-his-emissary/)

McGilchrist presents hundreds of studies to support his thesis of the divided brain. https://jotsandscribbles.blog/2023/11/18/dpes-mcgilchrist-provide-good-scientific-evidence-for-the-thesis-in-the-master-and-his-emissary/ But other scientists have raised questions and objections, especially on the discussion here: Full article: Engaging Iain McGilchrist: Ascetical practice, brain lateralization, and philosophy of mind (tandfonline.com)

Bottom up or top down?

A number of objections are about the generalisations McGilchrist makes. McGilchrist thinks these objections are a symptom of a scientific approach that is already left hemisphere dominated:  

Ultimately if the left hemisphere is the hemisphere of ‘what’, the right hemisphere, with its preoccupation with context, the relational aspects experienced, emotion and the nuances of expression, could be said to be the hemisphere of ‘how’. This perhaps explains why conventional neuroscience, being itself largely a manifestation of left hemisphere activity, has focused so much on what the brain is doing in which hemisphere, not in what way it does it in each hemisphere, thus, in my view, missing the significance of what it is trying to understand.

McGilchrist argues that asking the questions, ‘Why are there two separated hemispheres? and ‘How does each hemisphere function differently?’ are valid questions that yield useful answers even if they are not the questions that bottom up science working from neurons to areas to functional circuits would ask.

While I think this is true, the challenge is what would falsify the divided brain hypothesis. If there is no study that can be done showing cross hemisphere circuits or functional areas smaller than the hemisphere, then is this really a scientific theory?

Lesions or imaging?

Several people in the discussion Full article: Engaging Iain McGilchrist: Ascetical practice, brain lateralization, and philosophy of mind (tandfonline.com) brought forward evidence from more modern fine detailed imaging. This imaging shows circuits of activity that might have been missed by older imaging. It could also be argued that we cannot always read off normal function by examining how the brain functions with parts of it damaged. Particularly the argument about the divided brain suffers if we only get lopsided when one half is missing, but normally the two halves keep each other functioning normally.

Nonetheless, imaging has its own problems. Not all brain processing shows up as increases in overall activity. A “switch” in which the half of neurons in an area that were active were deactivated and the inactive half were activated might show no change in imaging. Increased activity might be a sign of general inhibition.

The objections raised are helpful in highlighting (what McGilchrist would acknowledge) that the “divided brain” is not fully divided, and that they do normally work together. The question is whether that evidence means that there is no evidence to helpfully consider the hemisphere’s distinctly, rather than simply focus on functional systems within the cortex.

Can the philosophical and cultural insights stand without the neuroscience?

If you find that McGilchrist’s approach the mind, and what it might say about culture, helpful, it may stand even if the science is less clear cut than he presents. No doubt the science will continue to be debated and progress will be made. But while there may be helpful insights into the human mind and society without evidence of the hemisphere differences, it is the rooting of these insights in neuroscience that gives them especial weight, and greater explanatory power.

In so far as I understand the evidence, I think McGilchrist’s thesis has a core of good scientific evidence. But further research may certainly change that (this is a fast developing area of research). And it seems likely that at points McGilchrist has simplified or over-applied things.

So I plan to think about implications for church and discipleship on the assumption that there is a helpful and true core to what McGilchrist is saying to prompt us to think further about what we do. But I will be tentative about most of my conclusions, recognising that “the science” I am applying is still under discussion. And underlying all of that, I assume the Bible is the true insight into the world to test all other insights by.