The science of lying: How human minds behave during the act of deception

People judge honesty or deception in the moment it happens, and the brain makes that determination very quickly. A new study shows that split-second patterns shared across two brains can flag when one person will accept a lie from the other.

Lead researcher Yingjie Liu, North China University of Science and Technology (NCUT), and colleagues examined how closeness and context shape these decisions.

They focused on whether messages framed as gains or losses sway us, and whether it matters if the sender is a friend or a stranger.

The team reports their results in a paper that monitored 66 adult pairs using a method called hyperscanning. They measured brain activity from both people at once while they exchanged information on networked screens.

Daily life, deception, and the brain

Most lab studies on lying isolate individuals, but daily life is social. This project looks at deception as it unfolds between two people who are sharing a task, and it tests how prior relationships change the calculation.

It also tracks interpersonal neural synchrony (INS) across the pair. INS is the moment by moment alignment of brain activity between two people.

Pairs sat face to face and relayed information through computers while the system recorded surface-level brain signals.

When the shared outcome of a choice helped both partners, the trial counted as a gain; when it harmed both, it counted as a loss.

The researchers then asked whether the receiver would accept the sender’s statement and how often acceptance depended on friendship or context. Across trials, people believed messages more in gain settings than in loss settings.

Brain signals in deception

The method used was functional near infrared spectroscopy (fNIRS), which tracks oxygenated blood changes near the cortex.

The analysis zeroed in on regions tied to evaluating risk, processing reward, and grasping another person’s intent.

The dorsolateral prefrontal cortex (DLPFC) helps weigh choices when risk is on the table.

Causal stimulation studies show it shapes the computation of subjective value under risk, as demonstrated in a recent study. Signals there related to careful evaluation matched the loss context.

The orbitofrontal cortex (OFC) contributes to assigning reward value and updating expectations during learning.

Its role in representing reward and non-reward has been mapped across species in a comprehensive review, and in this work OFC coupling tracked better with gain contexts.

A third area, the frontal pole, supports understanding intentions and long range planning. Together, these systems formed a network whose coupling differed by context and by whether the dyad contained friends or strangers.

Role of friendship

Friendship increased shared brain activity in task relevant regions. In gain settings, friends showed more coupling in the OFC, and in loss settings they showed more coupling in the DLPFC.

This coupling did not just mirror the context, it carried predictive power. Trial by trial, higher synchrony in the relevant region aligned with a higher chance the receiver would accept the sender’s statement, even when the statement was deceptive.

Related work with romantic partners offers a useful comparison point.

In deception tasks, couples show stronger brain-to-brain synchronization and lower rates of deceptive success compared with strangers, highlighting how relationship closeness reshapes vigilance.

Early signs of deception

One practical result stands out. The model based on shared neural activity predicted successful deception at the level of a single trial, and it did so from early moments in the exchange.

That fits with prior work arguing that the neuroscience of deception involves rapid control processes layered over memory and valuation. In other words, much of the outcome is decided before long deliberation kicks in.

Impact of deception on daily life

The pattern suggests two forces pulling in opposite directions. Gains invite trust, and closeness invites alignment, which can ease coordination but can also lower caution when caution is warranted.

This is not a claim that friends lie more or that friendship is unsafe.

It is a reminder that when a message promises upside and comes from a familiar face, the brain shifts its weighting toward reward signals and relationship cues, which may bias truth checks.

For science, detecting deception is not the end goal. The goal is to understand how people process social information so that we can improve training, design safer systems, and reduce harm in settings like finance, healthcare, and online platforms.

Future studies will need to test whether simple behavioral prompts can nudge evaluation back toward balance in tempting gain contexts.

They will also need to probe whether synchrony measures generalize beyond lab tasks to natural conversations, and how they interplay with culture and age.

The study is published in JNeurosci.

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