The human brain seems to be wired for forward-looking optimism.  In 2007, Tali Sharot and a team of scientists at University College London showed that people who were asked to imagine positive and negative future events consistently felt like the positive events are closer in time; the positive future events also felt closer than events in the past, whether positive or negative.  More recently, Dr. Sharot has turned her attention to the “good news/bad news effect”, our tendency to update our beliefs to reflect good news more than bad news.  Over the last few years, she and her team have identified the part of the brain responsible for this behaviour and even shown how to disrupt it.

In her research, Dr. Sharot measures the strength of the good news/bad news effect by checking the difference in how likely volunteers guess a negative event is before and after they are told the actual likelihood for someone in their circumstances.  Those who receive good news (i.e., the negative event is less likely than they thought) adjust their estimates more than those who receive the bad news that the event is more likely.  This is true for everything from mild events (like missing a flight) to more significant cases such as being subjected to violence or diagnosed with a serious medical condition.  Other factors, including how rare an event is or whether volunteers have had personal experience with it, also don’t affect this tendency — good news gets preferentially incorporated into our beliefs, having twice as much impact as bad news in one of the studies.

To identify the regions of the brain that might be mediating this effect, Dr. Sharot and her team used functional magnetic resonance imaging (fMRI) to measure the volunteers’ brain activity while they were being subjected to the test.  By recording the flow of oxygen-rich blood in the brain, fMRI gives researchers an idea of which regions are active.  Three different areas lit up when people were adjusting their beliefs based on good news: the left inferior frontal gyrus (IFG), the medial frontal cortex/superior front gyrus (MFC/SFG), and the right cerebellum.  When volunteers heard bad news, the IFG lit up again but this time on the right side; the right side of the IFG also had a weaker response in people who scored higher on a test of optimism.

The next step was to interfere with these regions and measure the effect on people’s behaviour.  Dr. Sharot and her team decided to focus on the IFG, using transcranial magnetic stimulation to influence the left and right IFG independently.  By generating a magnetic field near these regions, the team could temporarily inhibit their activity while testing volunteers’ bias towards good news.  Once again, the participants were more likely to assimilate information that provided an optimistic update, but only if the right IFG was interfered with. Participants who had their left IFG inhibited no longer showed a preference for good news, being equally likely to incorporate bad news into their outlook. Since reducing the activity of the left IFG weakens the good news/bad news effect by allowing bad news to have the same weight as good news, Dr. Sharot concluded that the normal activity of the left IFG somehow generates a bias by blocking the incorporation of bad news.  While there’s still more work to be done in understanding exactly how this happens, these two studies have taken an important step by defining the neural basis for our bias towards good news.

Our tendency to discount bad news may actually be a good thing, since it encourages explorative behaviour and reduces stress and anxiety; as Dr. Sharot points out, depression tends to be associated with the absence of the good news/bad news effect, suggesting it may play an important role in our well-being.  Nevertheless, understanding the mechanism behind this behaviour is important, if only because it enhances our understanding of ourselves.  I also can’t help but think that this might somehow be linked with confirmation bias and to behaviours like gambling.  If that’s true, then a better idea of what’s happening in the brain of a gambler might be useful in finding ways to help them.

Refs
Sharot, T., Riccardi, A., Raio, C., & Phelps, E. (2007). Neural mechanisms mediating optimism bias Nature, 450 (7166), 102-105 DOI: 10.1038/nature06280

Sharot, T., Korn, C., & Dolan, R. (2011). How unrealistic optimism is maintained in the face of reality Nature Neuroscience, 14 (11), 1475-1479 DOI: 10.1038/nn.2949

Sharot, T., Kanai, R., Marston, D., Korn, C., Rees, G., & Dolan, R. (2012). Selectively altering belief formation in the human brain Proceedings of the National Academy of Sciences, 109 (42), 17058-17062 DOI: 10.1073/pnas.1205828109