Monday: normal brain. Tuesday: still normal. Wednesday: everything changed. Not because you discovered a hidden genius mode, sadly, but because scientists found a sharper way to watch a decision unfold - not as one blurry "I choose the left button" moment, but as a five-step relay race where everyone pretends this was the plan all along.
The paper, by Gabriel Weindel, Jelmer Borst, and Leendert van Maanen in eLife, asks a deceptively pub-quiz question: when you make a quick visual decision, what actually fills the time between seeing the thing and pressing the button? The obvious answer is "thinking." Which is like answering "weather" when someone asks why a tornado relocated your patio furniture.
The Usual Problem: EEG Is a Crowd at Last Call
Electroencephalography, or EEG, records electrical activity from the scalp. It is fast, noninvasive, and gloriously messy. Imagine trying to identify one conversation in a packed bar while every table debates fantasy football, mortgage rates, and whether tomatoes belong in fruit salad. That is EEG.
Traditionally, researchers average many trials together to find event-related potentials, brain responses linked to a stimulus, thought, or movement. Averaging is useful, but it can flatten individual weirdness. If one decision takes 400 milliseconds and another takes 800, lining them up too neatly can turn real timing into neurological mashed potatoes.
Weindel and colleagues used hidden multivariate pattern analysis, or HMP, which looks for repeating EEG patterns that occur in sequence but can shift from trial to trial. Think of a jigsaw puzzle where the pieces keep arriving late, but always in the same order. Rude puzzle, good science.
Five Tiny Plot Points
The team had people perform a visual decision task while EEG recorded the action. Then they modeled each trial as a sequence of hidden events. The result: five recurring events.
Two looked like visual encoding steps - the brain registering the stimulus, then processing what it saw. The next three lined up with attention orientation, decision commitment, and motor execution. So your brain does not simply see-choose-move. It does a "receive the clue, squint at the clue, point the mental flashlight, commit, hit the buzzer" routine. Very trivia night.
The clever bit is that the researchers changed stimulus contrast. Dimmer stimuli should slow early sensory processing. And they did. The timing between encoding and attention followed Piéron's law, a classic rule saying reaction time drops as stimulus intensity rises. Later, the interval from attention to decision followed Fechner's law, which links perceived intensity to physical intensity. Translation: early brain handles raw signal strength, while later decision machinery deals with perceived evidence. The brain is apparently doing both electrical engineering and vibes.
The Parietal Ramp Enters, Looking Suspiciously Like a Decision
The final decision-related event showed up as a ramping signal over parietal areas. Ramping matters because decision neuroscience often describes choices as evidence accumulation: the brain gathers noisy clues until one option has enough points to win. Like Scrabble, but the tiles are photons.
That ramp was not decorative brain confetti. Its timing, amplitude, and build-up predicted accuracy. Faster or stronger ramping gave clues about whether participants would get the decision right. This fits broader work showing that EEG and related methods can track decision formation in humans with finer timing than older approaches allowed.
It also speaks to a current headache: separating perception, attention, decision, and movement. Reaction time is one number, but it hides several processes. If someone responds slowly, did they see poorly, attend late, deliberate longer, or move slowly? Reaction time is a scoreboard with no box score.
Why This Could Matter Outside the Lab
If this approach holds up across tasks, groups, and messier real-world conditions, it could help researchers pinpoint which stage of decision-making goes sideways. That matters for aging, attention disorders, neurological disease, fatigue, and testing where "slow response" is too blunt a label. Two people can take the same extra 200 milliseconds for different reasons. One brain may encode slowly; another may encode fine but delay commitment. Same stopwatch, different culprit.
This does not mean EEG is about to read your mind at the grocery store and judge your cereal choices. Please relax, Captain Crunch remains between you and your conscience. But it does suggest that noninvasive brain recordings can reveal the moving parts of a decision with more precision than a single reaction-time number ever could.
A "decision" feels instant from the inside, but from the outside it looks staged. Vision sets the props. Attention turns on the spotlight. Evidence piles up. Motor systems get ready. Then you press a button and tell yourself, with magnificent confidence, that you simply chose.
References
Weindel G, Borst JP, van Maanen L. Decision-making components and times revealed by the single-trial electroencephalogram. eLife. 2025;14:RP108049. https://doi.org/10.7554/eLife.108049. PMCID: PMC12755882.
O'Connell RG, Kelly SP. Neurophysiology of Human Perceptual Decision-Making. Annual Review of Neuroscience. 2021;44:495-516. https://doi.org/10.1146/annurev-neuro-092019-100200.
Duffy JS, Bellgrove MA, Murphy PR, O'Connell RG. Disentangling sources of variability in decision-making. Nature Reviews Neuroscience. 2025;26:247-262. https://doi.org/10.1038/s41583-025-00916-3.
Balsdon T, Verdonck S, Loossens T, Philiastides MG. Secondary motor integration as a final arbiter in sensorimotor decision-making. PLOS Biology. 2023;21:e3002200. https://doi.org/10.1371/journal.pbio.3002200. PMCID: PMC10393169.
Weindel G, Borst JP, van Maanen L. Trial-by-trial detection of cognitive events in neural time-series. Imaging Neuroscience. 2024. https://doi.org/10.1162/imag_a_00400. PMCID: PMC12315731.
Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.