My last post about this paper summarized the results. I want to talk briefly about the science behind it. I am not going into serious detail, but just to present an idea. So forgive any oversimplifications for those of you who know a lot about neuroscience.
When we make something up - not just lies or exaggerations but also daydreams and that kind of stuff - we use mirror neurons. Mirror neurons are a place where we can create simulations that do not become part of our long term memories. But they are of course connected because we need to use our basic cell assemblies to construct the simulations. It is in this connection that we get into trouble.
Over time, our brain is not able to differentiate which of these connections was part of a simulation and which ones were real. The simulations are weaker, so they have less of an effect on long term memory construction than real memories. But they still have the effect and over time can build up if you exaggerate (or lie, or daydream) a lot.
And knowing that this is happening doesn't help. We can't access the specific neuronal connections and delete them. Unfortunately, we can't control our brains to this level of detail. So our long term memories are stuck with the bad data.
And in order to be convincing in our exaggeration, we create supporting arguments. Even though we know these to be exaggerations too (otherwise, the exaggeration wouldn't be an exaggeration), we have multiplied the strength of the mirror neuron structure many times over. So whatever impact it has on long term memory is multiplied.
Another factor that makes this work is called cognitive dissonance. This is when two thoughts that we have are in conflict. For example, when we exaggerate we know that it is dishonest. And we don't like to think of ourselves as dishonest. So unconsciously, our brains try to convince ourselves that the exaggeration is really true. We feel better as a result. But then, the mirror neuron schema is treated more like a real one and has an even stronger impact on long term memory. The problem just gets worse.