Your Brain Hates Not Knowing

Why can not knowing what will happen often feel worse than knowing that something bad has already taken place? This is not to say that uncertainty is always worse than bad news; this is where neuroscience comes into play. Uncertainty can be particularly difficult because it prevents the brain from knowing the ‘what, where, when, and how’ of any possible threat, making it harder to decide how to prepare.

Waiting for an exam result is a weight we have all dealt with. Not knowing what weeks of sleepless nights have earned you on a twenty-point scale can feel worse, for some, than being told you scraped a seven or worse. The brain does not necessarily prefer bad news, but it struggles with the inability to predict what comes next.

Our brains are constantly trying to predict the future. From anticipating the ground beneath our feet to predicting how someone will respond to a message, we use our previous experiences to build expectations. When reality differs from these expectations, the brain registers a prediction error and updates its model of what is happening. Uncertainty makes this process harder because less information is available to make an accurate prediction. Instead of knowing which outcome to prepare for, the brain has to keep several possibilities open, increasing attention as it searches for information to resolve the uncertainty. In this sense, uncertainty is not just a lack of knowledge but an ongoing problem for the brain: what is going to happen, and how should I prepare for it?

Unpredictability can take several forms: risk when possible outcomes and their probabilities are known; ambiguity when there is insufficient information to estimate those possibilities; and threat anticipation when we are waiting for a potentially negative outcome. A 2019 meta-analysis of 87 functional magnetic resonance imaging (fMRI) studies examined how not knowing is processed across threat and reward, decision-making, and associative learning. Despite these different contexts, the bilateral anterior insula (located deep within the brain’s lateral grooves) was consistently involved, suggesting a broader role in monitoring unpredictable outcomes. Other regions, including the amygdala and anterior cingulate cortex, were recruited depending on the context. The amygdala was particularly involved when uncertainty carried emotional or potentially threatening significance. Rather than having a single ‘uncertainty centre,’ the brain therefore appears to rely on a network that monitors the environment, evaluates possible outcomes, and helps adapt behaviour when predictions are unreliable.

The unknown itself is not inherently negative. Not knowing what will happen can also drive curiosity, exploration, and learning. The problem arises when uncertainty is paired with the possibility of a threat, particularly when the situation feels important or uncontrollable. In these circumstances, the brain’s monitoring systems can become more vigilant, explaining why waiting for an important result can become mentally exhausting.

When uncertainty involves a possible threat, it can also trigger the brain’s stress response. The amygdala can signal the hypothalamus to activate the Hypothalamic-Pituitary-Adrenal (HPA) axis, eventually leading to cortisol release, which increases alertness and helps the body respond to a challenge. In the short term, this is adaptive: heightened alertness can help us notice new information and prepare to act. But unlike a clear threat, uncertainty has no definite endpoint. The brain may therefore remain prepared for something that has not happened — and may never happen. This could explain why simply waiting can leave us tense, restless, or physically anxious, even in the absence of an actual threat.

Maybe the worst part is not bad news — it’s waiting for it. While nothing has happened, your brain is already preparing for everything that could. Uncertainty leaves the story unfinished — and your brain hates an unfinished story.

Image from Wikimedia Commons