Detecting spontaneous deception in the brain

Abstract

Deception detection can be of great value during the juristic investigation. Although the neural signatures of deception have been widely documented, most prior studies were biased by difficulty levels. That is, deceptive behavior typically required more effort, making deception detection possibly effort detection. Furthermore, no study has examined the generalizability across instructed and spontaneous responses and across participants. To explore these issues, we used a dual-task paradigm, where the difficulty level was balanced between truth-telling and lying, and the instructed and spontaneous truth-telling and lying were collected independently. Using Multivoxel pattern analysis, we were able to decode truth-telling versus lying with a balanced difficulty level. Results showed that the angular gyrus (AG), inferior frontal gyrus (IFG), and postcentral gyrus could differentiate lying from truth-telling. Critically, linear classifiers trained to distinguish instructed truthful and deceptive responses could correctly differentiate spontaneous truthful and deceptive responses in AG and IFG with above-chance accuracy. In addition, with a leave-one-participant-out analysis, multivoxel neural patterns from AG could classify if the left-out participant was lying or not in a trial. These results indicate the commonality of neural responses subserved instructed and spontaneous deceptive behavior as well as the feasibility of cross-participant deception validation.

Keywords: angular gyrus; deception detection; inferior frontal gyrus; lying; multivoxel pattern analysis.

FIGURE 1

(a) An illustration of used visual stimuli in Task1. (b) An illustration of the material database created for Task2

FIGURE 2

An illustration of the run and trial procedure. (a) Each run consisted of four blocks, three designed for Task1 and one for Task2 (in a pseudo‐randomized order). (b) In each block, a probe specifying upcoming task was presented from 8 to 12 s. Next, in each trial, four phases were presented successively (i.e., the presentation of instruction, visual stimuli, statement, and feedback). In both T1Te and T1L conditions, simple statements were utilized. Whereas in the T1Td condition, simple statements were replaced with complex statements. (c) During Task2, participants were free to tell the truth or lie on specific trials. The used statement was modified according to task requirements. The timeline for each phase was identical to other conditions from Task1. Abbreviations: T1L, lying condition from Task1; T1Te, truth‐telling‐easy condition from Task1; T1Td, truth‐telling‐difficult condition from Task1; T2L, lying condition from Task2; T2T, truth‐telling condition from Task2

FIGURE 3

(a) In the within‐participant cross‐task analysis, the classifiers were trained with T1Td and T1L and then used to distinguish T2T from T2L for each participant. The performances of the within‐participant crosstask classifiers were examined on the average accuracy across 21 participants. (b) Cross‐participant crosstask analysis was conducted based on the leave‐one‐participant‐out (LOPO) scheme, resulting in 21 folds. For each fold, classifiers were trained with T1Td and T1L collected from 20 participants and then used to distinguish T2T from T2L in another participant who was left out for testing. The performance of the crossparticipant cross‐task classifiers was attested to the average accuracy across 21 folds

FIGURE 4

The accuracy of each condition in Task1. The accuracy rate from T1Te was significantly higher than both T1Td and T1L. There was no significant difference between T1Td and T1Te

FIGURE 5

(a) Within‐participant cross‐task validation was conducted in three functional ROIs, namely the right angular gyrus (AG), right inferior frontal gyrus (IFG), and left postcentral gyrus (PoCG). Results showed that accuracy rates in classifying T2T and T2L from the right angular (AG), right inferior frontal gyrus (IFG) but not left postcentral gyrus (PoCG) were significantly higher than chance level (50%). (b) Cross‐participant cross‐task validation was conducted in three 8‐mm spherical regions, centered on the coordinates of the prior functional ROIs. Results showed that accuracy rates in classifying T2T and T2L from the right angular gyrus (AG) but not right inferior frontal gyrus (IFG) and left postcentral gyrus (PoCG) was significantly higher than the chance level (50%)