Patricia noticed it first during her morning commute. As she walked down the familiar path to the subway, her hand automatically reached into her tote bag for the MetroCard—except she had switched to the Metro company’s new digital wallet App.
Her fingers closed around the air, and for about 300 milliseconds, she petrified. “Am I still on Earth?” Her inner sci-fi writer mode activated before her prefrontal cortex. After a few seconds, she remembered the switch and tapped her phone against the turnstile.
Brain, the Prediction Machine
More than a habit or procedural memory (a.k.a., “muscle memory”, although it neither stores in muscle, nor is strictly related to motor skills). What Patricia experienced may be her built-in fortune teller at work.
The leading theory explaining the predictive brain is “predictive coding.” The theory can be traced back to as early as Hermann von Helmholtz’s 1860 concept of “unconscious inference,” which described perception as the brain’s use of prior knowledge to interpret sensory input.
In 1999, a further formalization for cortical processing was developed by Rajesh Rao and Dana Ballard, proposing that the brain constantly predicts sensory inputs and updates its interpretation based on errors.
A 2021 meta-analysis provides the database for this theory, illustrating that the human brain is constantly engaged in predicting its upcoming states and refining these predictions through error signals.
Other modalities currently attracting research interest include active inference and effective inference, among others. Recent literature underscores both their potential and the challenges they present. A 2023 review assessed how well these modalities perform in practice, while another 2023 review offered a broader introduction.
How Does Prediction Work, Exactly?
Cut back to the metro. What happened to Patricia was that the predictive process worked through “hierarchical message passing.”
Imagine our brain has different levels, like floors in a building. The higher floors, areas that process complex, abstract information, are constantly sending messages down to lower floors that handle basic sensory input. These downward messages are predictions: “Based on everything I know, here’s what I expect to happen next.” Meanwhile, the lower floors send messages back up, but only when something doesn’t match the prediction. These are called “prediction errors.”
This process happens through specific neural mechanisms. Neurons that carry predictions downward use different neurotransmitters and connection patterns than those carrying error signals upward. The predictions tend to flow through deeper layers of brain tissue, while errors travel through more superficial layers, creating a two-way neural highway that’s constantly negotiating between expectation and reality.
At the macro level, we’re constantly running longer-term predictions: anticipating career changes, planning for retirement, predicting how technological shifts might affect our industries. These extended predictions engage different brain regions and involve higher function.
Motor cortex imagery studies have also shown that musicians and athletes activate the same brain circuits during mental rehearsal as they do during actual performance. When a pianist imagines playing a complex passage or a gymnast visualizes a routine, their prediction systems are literally running the motor programs, strengthening the neural pathways that will be used during real performance.
Do We Have a Different Reality?
We’ve all shared Patricia’s experience at one time or another. But do we all predict in the same way? Predictive theories suggest that the brain constantly weaves past knowledge together with new information to anticipate what comes next. Yet because each person’s “predicted reality” is filtered through their own history and perspective, it can sometimes feel as if we’re living in different universes.
To trace these differences across the lifespan, a recent study examined how predictions differ between age groups through the lens of language comprehension. Older adults may not rely on prediction as consistently as younger adults, instead drawing on predictive strategies only in certain contexts.
Similar variability appears in childhood as well: An interesting study in 2022 investigated children’s drawings and showed that individual differences may reflect different developmental trajectories in these predictive processes, suggesting a unified predictive coding framework for both general and individual drawing development.
Besides age and development, individual confidence may shape predictions as well. A 2024 study suggests that confidence may shape predictions; the more confident participants felt, the stronger their brains reacted when faced with the unexpected.
In the study, the activity levels in key brain regions, such as the ventral visual stream and anterior cingulate, shifted depending on both the predictability of the sequence and the participant’s confidence. That was because humans naturally learn patterns from sensory input and, based on which, anticipate what comes next.
So, given that we receive sensory information at a 1 billion bits per second rate across all eight senses, are we living in a constant forecast?
When Predictions Go Wild
These predictions are fundamental operations of consciousness, as part of our brain’s default factory setting. A 2021 study found that predictive processing is deeply embodied and affective, meaning our brain actively predicts, based on real-time sensations, emotions, environmental factors, and beyond.
However, just like any other high-functioning machinery, the precision of the system also makes it vulnerable to error.
Prediction error occurs when the brain’s expectations do not match incoming sensory information, creating a ‘surprise’ signal that draws attention and triggers learning. They can also contribute to habitual, inaccurate patterns of thinking that skew perception negatively and cause us to see the world with more biases. An interesting 2024 article has explored how prediction errors could impact our memories and revealed that the magnitude of prediction error determines whether we update existing memories or create entirely new ones.
Small prediction errors help the brain update existing knowledge by integrating new information into established memory structures. In contrast, large prediction errors suggest a fundamentally different situation, prompting the brain to create a separate memory rather than altering the previous one. As a result, our memory organization depends not only on what we experience, but also on how surprising those experiences are compared to our expectations.
Yet beyond shaping memories, the errors also constitute cognitive distortion. In a 2023 article about CBT (Cognitive Behavior Therapy), the term “fortune-telling” is used to identify a cognitive distortion when analyzing patients’ thoughts.
Moving further in the context of mental health, the prediction errors may be even more insidious. A 2024 neuroimaging study found that negative cognitive biases in depression relate to altered learning from prediction errors, with increased neural tracking of negative prediction errors in the insula, demonstrating how prediction errors can lead to maladaptive belief updating
Language and Social Life
While prediction errors can trap us in cycles of negative thinking, the predictive system itself (when functioning well) powers some of our most human capabilities. A 2024 review has shown that prediction is crucial for language comprehension. When you read this sentence, your brain is constantly predicting what word comes next based on context and your knowledge of grammar and meaning. The ease with which you understand language depends on how well your predictive system has learned these patterns.
In social situations, predictive processing shapes how we perceive others. A recent review has shown that the hierarchical predictive processing, especially, provides a powerful framework that explains how prior expectations and social knowledge shape intergroup perception and cognition.
Do Furry Friends Also Predict?
Patritia went back home after working, and as usual, her stress melted at the front door as her beloved (and cheesy) Luna meowed to celebrate her triumphant return from hunting. Luna expects treats and petting right after Patricia changes into her apartment clothes. So, does she also live in a world of constant forecasting?
Watch a cat stalking a toy mouse. The cat’s brain is constantly forecasting where the toy will be next, predicting the optimal moment to pounce. Dogs also anticipate their owners’ routines, heading to the door before the human has even consciously decided to go for a walk.
Current literature generally supports associative learning and conditioning to explain most of their routine. But why can some pets seem to predict weather changes, natural disasters, and human illness? While there is no definite proof, animals do have highly evolved sensitivity to sensory input–sounds, smells, lights, electromagnetic fields, atmospheric pressure…
That said, they may experience the world quite differently. For example, cats can hear frequencies from around 45 Hz up to about 64,000–85,000 Hz, and dogs hear from about 67 Hz to 45,000–60,000 Hz; we humans, in contrast, can hear from around 20 Hz up to 20,000–23,000 Hz. They hear high frequencies that signal changes or dangers and adapt accordingly for survival, while we interpret it as folklore about their forecasting abilities.
Editor: Uhm… Where Is My Tarot Cards?
To decide the next topic, I pull out my tarot, and voila, a six of wands, what does that mean…
Cut back to reality, we all want to predict the future so we can be less anxious and actually embrace the uncertainties (if anyone can do that), but our predictions reflect who we are through that “sensory input + experience” formula more than the objective truth. Thus, our behaviors, shaped by the prediction, shape our reality and further enhance who we are.
Although human cognitive abilities may surpass those of animals, recent animal studies continue to reveal surprising insights. Remain humble and respect our animal counterparts; we will continue to share the Earth with them for a while.
