Most of us assume the brain can clearly separate what is real from what is imagined. Fact seems stable and objective, while fiction seems invented, distant, and unreal. But the brain does not work with reality in such a simple way. Whether we are seeing the world, imagining an image, or becoming absorbed in a story, the brain is still creating an experience from the information it receives. This makes the boundary between fact and fiction less obvious than we often think.
The reason imagination can feel so real is that the brain may not process it as something completely separate from perception. Studies led by Joel Pearson at the University of New South Wales suggest that the same brain pathways code for both imagination and perception, with imagination acting like a weaker form of perception (1, 2, 3). This makes sense when we consider vision. Around 70% of the information we receive comes through sight: visual information enters through the retina, travels to the occipital lobe at the back of our head, and is decoded by the brain into a complete image. But imagined images are also formed inside the brain, even though they have no external input. One begins in the outside world; the other begins internally. Yet both are reconstructed by the brain, and both exist as images within it. The question becomes less about whether imagination is ‘fake’, and more about whether the brain can always recognise that difference. This is why a dream can feel real right until we wake up, or why imagining a situation can make us nervous before anything has actually happened (1, 4). The brain may only realise the difference once reality interrupts it. Until then, imagination is still an experience the brain has to respond to.
The placebo effect shows that the brain does not simply dismiss something because it is not physically real. The word placebo comes from the Latin meaning “I please”, and in medicine, it refers to a ‘fake’ treatment given without an active drug ingredient. At first, this seems like a purely psychological trick: the patient believes they are receiving treatment, so they feel better. However, research by Jon-Kar Zubieta, published in The Journal of Neuroscience, challenged this assumption. His study found that when patients were given a painkiller placebo, their brains released natural pain-relieving chemicals, known as endorphins. Studies on placebo analgesia have shown that this belief in treatment can itself activate endogenous opioid systems in the brain (5, 6). This overturned the idea that the placebo effect was only a matter of belief or imagination; the placebo did not work because the medicine was real, but because the brain responded as if it was.
If the brain struggles to separate fact from fiction unless it is clearly corrected, then imagination becomes something we can use, not just something we experience. We can use this to mentally simulate nerve-wracking situations before facing them, or even to picture ourselves achieving future goals so they feel more possible and familiar (1, 4).
The same idea also applies to perception. The famous blue-and-black or white-and-gold dress showed that even vision is not just a direct copy of reality. The dress was physically blue and black, and the same light from the dress entered people’s retinas. But the brain does not stop at the retina. It has to interpret the visual information it receives, including assumptions about light and shadow (7). On one hand, people who saw blue and black interpreted the dress as being lit from the front, so their brains kept the darker colours. On the other hand, people who saw white and gold interpreted the dress as being in shadow, with light coming from behind it, so their brains ‘corrected’ the image differently. This means they were not seeing a different object; their brains were making different predictions about the same object.
The same problem appears beyond visual perception. People often believe they are seeing issues objectively, when their brains are already filtering information through unconscious bias. Psychologist Emily Pronin describes this as a “bias blind spot”: people can recognise bias in others more easily than in themselves (8). This helps explain why people can look at the same evidence but walk away with completely different conclusions. Their brains are not just receiving facts; they are selecting and interpreting them in ways that fit existing beliefs.
This has serious consequences beyond optical illusions. If perception is already filtered through assumptions, then memory and judgement are also less objective than we like to believe. Eyewitness accounts, for example, can feel completely sincere while still being inaccurate, because the brain does not record events like a camera. It reconstructs them, filling in gaps with expectation, emotion, and later information (9). The same pattern helps explain why misinformation spreads so easily (10). When people encounter complex or uncertain information, the brain often shortcuts the process by relying on what feels familiar, emotionally convincing, or consistent with what they already believe. In this way, false information does not always persuade us because it is carefully reasoned; it often works because it fits neatly into a mental story the brain has already begun building.
Neuropsychologist and neurobiologist Roger Sperry once said, “Before brains, there was no colour or sound in the universe, nor was there any flavour or aroma and probably little sense and no feeling or emotion” (11). Reality may exist outside us, but experience is made inside the brain. So if our brains are constantly interpreting, imagining, and filling in gaps, then fiction is not meaningless at all. It is one of the ways the brain practises, believes, and builds reality.
References
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Sperry RW. Problems outstanding in the evolution of brain function. James Arthur Lecture on the Evolution of the Human Brain. 1964. https://people.uncw.edu/puente/sperry/sperrypapers/60s/107-1964.pdf
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