Brain signals can reveal when a person is preparing to lie before they say a word. Recent research published in journals neuroimage Explore how the brain primes us to communicate falsehoods. This finding suggests that just predicting a lie requires a distinct mental effort that the sensor can detect.
The science of lie detection has a long and difficult history. Traditional methods of measuring physical signs of stress, such as polygraphs, have been widely criticized for being unreliable. In recent years, researchers have increasingly turned to brain imaging techniques in search of more objective indicators of deception.
Most of this previous research focused on the brain activity that occurs during the act of lying itself. However, in everyday situations, people often give off subtle warning signs before lying. The question begins, prompting the brain to prepare a deceptive response before a word is even spoken. This preparatory step has received little scientific attention.
The researchers set out to determine whether preparing to lie leaves a discernible trace in brain activity. They wanted to know whether these signals could ultimately contribute to new approaches to deception detection. The researchers also sought to create a more realistic experimental scenario than many previous studies by investigating lies about personal information rather than arbitrary topics such as furniture.
A research team led by Emily Volz of the University of Bonn recruited 32 participants for the experiment. While completing the deception task, participants wore a hat fitted with a sensor that recorded their brain’s electrical activity. They were shown clue words such as “place of birth” and “address” that indicated the category of the upcoming personal question.
Each participant was assigned one category in which they were instructed to lie and answer honestly for the other categories. For example, a participant assigned the category “Country of Origin” might see the statement “Country of Origin = Germany?” You are expected to answer “yes” even if the statement is false. The cue appeared two and a half seconds before the question, allowing time to prepare a deceptive response. Across the two blocks of trials, a quarter of the prompts required a lie and the rest required telling the truth.
The researchers found that cues announcing an upcoming lie caused clear and measurable differences in brain activity before the question appeared. Several neural markers related to attention and preparation became more prominent after the lie cue. Brain signals associated with shifting attention, deeper cognitive processing, and anticipating events all increased.
At the same time, alpha power, a pattern of brain activity often associated with neural idleness, decreased. This decline suggests that the brain was mobilizing cognitive resources to cope with the greater mental demands of deception. The authors concluded that these findings indicate “enhanced mobilization of cognitive resources in the period leading up to deception” and highlight the potential benefits of studying the preparatory phase rather than the mere act of lying.
The researchers also investigated whether these neural signals could identify which categories of personal information each participant lied to. The researchers combined the three most informative measures to accurately identify the lie category in 24 of the 32 participants. Seven cases were inconclusive, and the system misclassified only one. This suggests that preparatory brain signals contain meaningful information that may support future lie detection approaches.
Several limitations should be considered when interpreting these results. For example, rather than voluntarily choosing to lie, participants were instructed when to lie. This setting makes the task less representative of real-world deception, where people decide for themselves whether to tell the truth.
The paper, “(Don’t take it personally: Brain wave markers that prime you to lie about autobiographical questions”), was authored by Emily Volz, Jonas Schmuck, Robert Schnurch, and Henning Gibbons.
