The brain science behind storytelling – Part 1

Pedro Almeida | October 26, 2017

Our friends from Unilever have invited us for a session on the brain science behind storytelling, along with a showcase of part of the pilot we did with them. In the upcoming two posts I’ll be telling about the stuff I showed them. Although the link was not immediately evident, it turned out as a great opportunity to present some nice research on why we, as humans, build stories, and connect it with what we do at MindProber. Being a session on storytelling, we shared some stories from Cognitive Neuroscience and Social Psychology, with the overall message that actually building narratives results from a multifaceted set of skills that have conferred humans adaptive fitness on many levels throughout evolution. Some of the reasons why this is so may be both surprising and humbling. So these were the stories, along with the lessons, I told them:

Brain lesions

Split Brain Patients

The first story was about brain lesions. I shared the cases of split brain patients, famously described by Michael Gazzaniga. These are patients whose corpus callosum (the main group of white fibers that connect both brain hemispheres) have been severed as a therapy for particularly serious cases of epilepsy, back in the old days. The curious thing about these patients is that, due to the particular neuroanatomy of visual pathways, it is possible to show isolated visual stimuli to the right and left hemispheres. Since the corpus callosum is severed, the processing of the stimulus is limited to each hemisphere.


Gazzaniga-slit-brainFollowing the footsteps of Nobel laureate Roger Sperry, Gazzaniga has shown several interesting things in these patients. With some exceptions, the left hemisphere (in right-handed people) can consciously understand written words and talk about whatever stimulus is being visualized, while the right hemisphere can’t. However, the right hemisphere can follow procedures if instructed, even if the patient is not aware why. For instance, if I show the word “face” to the left hemisphere the patient and ask him to read he will be able to answer “face” but if I show the same word to the right hemisphere the patient won’t report seeing anything. However, if I instruct him to draw what he sees with the left hand (which is controlled by the right hemisphere) he’ll draw a face, or, if I ask him to press a button with the left hand every time “face” appears, he will do so, even without being consciously aware of it.

The insightful element for storytelling comes from the observation that even if the individual is not aware of why he is performing a given behavior since he has been instructed through his right hemisphere, his left hemisphere confabulates, building a narrative that justifies his actions (Gazzaniga calls this the interpreter theory). On a widely known case, Gazzaniga and his team presented a split-brain patient with different words in each visual field and instructed him to choose an image that would fit what he saw from among a group of pictures. For example, when flashed the words “Music” to the left hemisphere and “Bell” to the right hemisphere, the patient would be aware of the word “Music” but not “Bell”.

However, when asked to choose from a group of pictures related to music, the patient would choose a bell tower. The cool thing is that, when asked to justify, the patient answered “Music – last time I heard any music was from the bells outside here, banging away” (see all the beautiful experiments here).

So, this was the first lesson: our left brain builds narratives to make sense of the world and our actions (even if the narratives are confabulated).

Primary visual cortex lesions

The second group of enlightening cases is about patients with lesions in the primary visual cortex. These patients have a condition known as cortical blindness: they are blind due to a brain lesion. A nice group of studies from Beatrice de Gelder’s labs suggest that these people process visual affective stimuli anyway. For instance, although these patients are not aware of the stimulus being shown to them, they are able to “guess” the emotional tone of the stimuli above chance level and show physiological emotional responses to the stimuli.

These results have been interpreted at the light of the dual-route model for emotional vision, popularized by Joseph LeDoux, where it is suggested that there are at least 2 visual pathways: one cortical, slower and that usually results in visual awareness, and another subcortical, faster and that does not result in visual awareness. (This brought me back to my academic work, were we were looking at emotional processing through each of these pathways in psychopathy).

So, lesson number two: effective information is processed at a subconscious level and exerts impact on our responses. 

I followed on this lesson with a story on the power of affective processing, by highlighting the research tradition on both implicit and explicit evaluative conditioning. These effects were first popularized by studies on suboptimal affective priming by Robert Zajonc. He showed that if he paired positive and negative stimuli with neutral images, those would contaminate the judgment of the neutral pictures (in other words, participants report liking more the pictures paired with the positive stimuli and less the images paired with the negative stimuli). These effects happen both when the effective pictures are presented consciously or unconsciously.

Then, I showed that emotional information also affects moral judgment, by highlighting Joshua Greene’s work on the neural bases moral reasoning using an ethical thought experiment known as the Trolley Problem. Back in the 60’s Philippa Foot introduced the modern version of a classical thought experiment in ethics that goes along these lines:

“There is a runaway trolley barreling down the railway tracks. Ahead, on the tracks, there are five people tied up and unable to move. The trolley is headed straight for them. You are standing some distance off in the train yard, next to a lever. If you pull this lever, the trolley will switch to a different set of tracks. However, you notice that there is one person on the side track. You have two options: Do nothing, and the trolley kills the five people on the main track. Pull the lever, diverting the trolley onto the side track where it will kill one person.  Which is the most ethical choice?”

Judith Thomson, in her turn, produced multiple versions of this problem. One of them, “The fat man” reads like:

“As before, a trolley is hurtling down a track towards five people. You are on a bridge under which it will pass, and you can stop it by putting something very heavy in front of it. As it happens, there is a very fat man next to you – your only way to stop the trolley is to push him over the bridge and onto the track, killing him to save five. Should you proceed?”

It has been shown that participants typically say they would change the train track on scenario 1, but wouldn’t push the fat man in scenario 2. Why is this, given that the utilitarian outcome of the situation is the same?

Greene showed that actually scenario 2 (and similar others where directly harming others is imagined) activates brain areas usually involved in emotional processing and this biases moral judgements (we could also mention the amazing work on moral dumbfounding by Jonathan Haidt where, among other things, it is shown that people produce strong intuition-driven moral responses that sometimes can’t justify when challenged, or the great work on the dependence of moral reasoning on brain regions typically related to emotional and social cognition by Jorge Moll, but had no time to).

So, the third lesson was: effective information shapes our attitudes and moral judgments, even if we’re not aware of it.

I guess the most shocking lesson came from Benjamin Libet’s controversial work. In a ground-breaking seminal experiment he asked subjects wearing an EEG cap to move a finger while looking at a clock, and then to signal on the clock when they had decided to move the finger. The amazing result was that a brain response (termed Readiness Potential) could be detected hundreds of milliseconds before subjects reported having the intention.

The fourth and most brutal lesson was: we build narratives to justify our actions, to build a story that places our intentions as the causes of our actions, when in fact “we” don’t cause them (whatever “we” is).

After these stories, the question then became “why?”. Why do we need to tell stories and what do we, as a species, gain from doing so? This is clearly not the full story, but I mentioned that building narratives can be a highly adaptive by-product of a great trick we as humans do: describe physical motion using what Daniel Dennett has termed the intentional stance. I showed Heider and Simmel’s stimuli, from an experiment back from the 1940’s where they showed that people would automatically attribute intentional states to a bunch of moving triangles, squares and circles (and mentioned that actually autistic patients fail to do this), and highlighted the advantages such a trick confers: if we treat the other as an agent with intentional states, then we can make sense of their behaviour, we can simulate their intentional state, and this is a powerful weapon if you happen to be trying to cooperate with him, or cheat him, or prevent being cheated. And this is a neat trick when you’re a highly social species as we are. And if you do that to others, why not do that to yourself, by building narratives that explain your actions on intentional terms?

Of course, as I mentioned, this is not the full story, and storytelling should confer other adaptive advantages, such as the ability to transmit adaptive memes (as defined by Richard Dawkins, not Facebook or Reddit), through the creation and transmission of legends.

The final lesson then was: we like narratives that involve others.

This gave me the moto to the second part of the presentation, one that includes MindProber, and that I’ll share in another post.

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Pedro Almeida
Pedro Almeida

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