The authors have declared that no competing interests exist.
Conceived and designed the experiments: AM KJ MF WS AG IS. Performed the experiments: MF IS AM. Analyzed the data: AM KJ MF. Wrote the paper: AM KJ IS.
Deception has always been a part of human communication as it helps to promote self-presentation. Although both men and women are equally prone to try to manage their appearance, their strategies, motivation and eagerness may be different. Here, we asked if lying could be influenced by gender on both the behavioral and neural levels. To test whether the hypothesized gender differences in brain activity related to deceptive responses were caused by differential socialization in men and women, we administered the Gender Identity Inventory probing the participants’ subjective social sex role. In an fMRI session, participants were instructed either to lie or to tell the truth while answering a questionnaire focusing on general and personal information. Only for personal information, we found differences in neural responses during instructed deception in men and women. The women vs. men direct contrast revealed no significant differences in areas of activation, but men showed higher BOLD signal compared to women in the left middle frontal gyrus (MFG). Moreover, this effect remained unchanged when self-reported psychological gender was controlled for. Thus, our study showed that gender differences in the neural processes engaged during falsifying personal information might be independent from socialization.
The broadest definition describes deception as social behavior in which one person attempts to persuade another to accept as true what the deceiver believes to be untrue
One may question, however, the motivation behind lying and whether this motivation is the same for both sexes. Psychological studies claim that both men and women are equally prone to try to manage their appearance
Functional magnetic resonance imaging (fMRI) can allow researchers to link brain activity patterns directly to the cognitive or affective processes and behaviors they produce, including human deceptive behavior. Deception-related behavior was found to be associated with increased demands on the executive control system, such as allocating mental resources to processing task-relevant information (i.e., working memory – keeping truth in mind while lying), inhibitory control (i.e., suppressing truth), and guiding behavior in situations involving response conflict (i.e., task switching between truthful and deceptive responses; e.g.
From the neural perspective, lying thus seems to be a complex cognitive process and, as such, is likely to be influenced by gender, as a number of recent studies have shown sex differences in various cognitive tasks. Though numerous papers have revealed sex differences in behavioral studies (e.g.,
Gender differences in inhibitory control, the other component of deception, have been researched more often. Studies have provided ample behavioral evidence for greater impulsivity in men than in women. For instance, men use illicit substances more frequently and in greater quantities than women
We hypothesize that if women have an advantage in inhibitory control, as certain studies imply
Furthermore, it was demonstrated that brain regions which regulate cognitive control were more active during falsifying autobiographical information compared to nonautobiographical. Personal information is highly practiced and readily accessible, making it more difficult to suppress prepotent truthful responses
The second issue we tested was whether the postulated gender differences were a consequence of biological sex (and thus connected more to genetic code and evolutionary selection) or whether the differences were a result of an interaction between sex and various socialization factors, which may be reflected in psychological sex roles (e.g.,
We analysed mean accuracy rates (AR) and reaction times (RT) using two separate repeated-measures ANOVAs with within-subject factors: Instruction (lie vs. tell the truth), Content (general vs. personal), and between-subjects factor: Gender (women vs. men).
The analysis of AR revealed the main effect of Instruction (F(1,27) = 57.26; p<0.001) and Content (F(1,27) = 36.33; p<0.001) as well as the interaction of these two factors (F(1,27) = 7,94; p = 0.009). Subjects were less accurate when they had to lie (87.7%) in comparison to telling the truth (96.5%). They were also less accurate when replying to questions concerning personal (89.8%) compared to general information (94.4%). Neither Gender nor any interaction with this factor reached significance (see
Error bars represent standard error of the mean. No between-gender effect reached significance.
The analysis of RT revealed the main effect of Instruction (F(1,27) = 135.2; p<0.001) and Content (F(1,27) = 4.51; p = 0.043). Subjects answered significantly slower when they had to lie (2301 ms) in comparison to telling the truth (2021 ms). They were also slower when answering questions related to personal (2146 ms) compared to general (2177 ms) information. Again, neither Gender nor any interaction with this factor reached statistical significance (see
For RT additional analyses were conducted on differential RT i.e. RT when subjects’ had to lie minus RT when subjects’ had to tell the truth. We considered a within-subject factor of Content (general vs. personal) and between-subjects factor of Gender (women vs. men). Although the interaction Content×Gender did not reach significance (F(1,27) = 2.84; p = 0.103), in men differential RT for personal information were significantly longer (357 ms) than for general information (250 ms) (F(1,27) = 6.58; p = 0.016). No such differences were observed in women. However, differences between men and women in either personal or general content did not reach significance (see
Error bars represent standard error of the mean. In men, differential RT for personal information were significantly longer than for general information, whereas in women no such differences were observed.
In reference to previous studies showing brain areas involved in deception, we performed a “lie vs. truth” direct contrast comparison for general and personal information together. T-test contrast based analysis revealed brain regions involved in both lie conditions compared to the truth conditions: the insula bilaterally, the middle temporal gyrus (BA 21, 22) bilaterally; the left supplementary motor area (SMA, BA 6), the left occipital gyrus (BA 18), the left supramarginal gyrus (BA 40), the right inferior frontal gyrus (BA 47), the right middle frontal gyrus (BA10/46), and the right cerebellum (see
The activations are superimposed on a Colin27 template image in the MNI space. The colored bar represents t-values; L – left side; R- right side.
Brain Region | BA | MNI coordinates | Z-score | Clustersize | ||
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x | y | z | |||
L Insula | 13 | −33 | 24 | 0 | 7.2 | 3980 |
L SMA | 6 | −3 | 18 | 51 | 6.6 | |
R Inferior Frontal Gyrus | 47 | 48 | 21 | −3 | 6.5 | 771 |
R Insula | 13 | 39 | 18 | −3 | 5.9 | |
R Cerebellum | 30 | −63 | −27 | 5.7 | 2284 | |
L Occipital Gyrus | 18 | −24 | −102 | 0 | 5.7 | |
R Cerebellum | 6 | −57 | −12 | 5.6 | ||
R Middle Frontal Gyrus | 10/46 | 36 | 51 | 9 | 4.7 | 132 |
L Middle Temporal Gyrus | 21 | −60 | −39 | −3 | 4.4 | 99 |
R Middle Temporal Gyrus | 21 | 51 | −36 | −3 | 4.3 | 85 |
R Superior Frontal Gyrus | 6 | 33 | −6 | 63 | 4.1 | 34 |
L SupraMarginal Gyrus | 40 | −54 | −51 | 27 | 4.0 | 67 |
L Middle Temporal Gyrus | 22 | −60 | −54 | 18 | 3.7 | 59 |
All of the listed brain regions were cluster corrected at 10 contiguous voxels and met the significance threshold of p<0.05 (FWE). The x, y, z coordinates are the MNI coordinates. BA is the abbreviation for the approximate Brodmann’s areas; L is left; R is right; SMA is the supplementary motor area. Cluster size is the number of voxels activated in the regional cluster. Only the main peaks of activation within each cluster and their corresponding brain structures are reported.
Brain Region | BA | MNI coordinates | Z-score | Clustersize | ||
General Information | x | Y | z | |||
L Cerebellum | −3 | −75 | −27 | 5.92 | 170 | |
R Cerebellum | 9 | −72 | −36 | 3.83 | ||
R Caudate | 9 | 6 | 15 | 5.37 | 82 | |
R Thalamus | 15 | −15 | 0 | 3.97 | ||
L Inferior Frontal Gyrus | 45/47 | −39 | 27 | 0 | 5.18 | 1087 |
L Insula | 13 | −33 | 21 | −9 | 4.70 | |
R Inferior Frontal Gyrus | 46/47 | 48 | 21 | 0 | 5.09 | 404 |
R Middle Frontal Gyrus | 45/46 | 33 | 15 | 36 | 4.48 | |
R SMA | 6 | 6 | 12 | 57 | 4.96 | 503 |
L SMA | 6 | −3 | 18 | 51 | 4.66 | |
L Occipital Gyrus | 17 | −15 | −96 | −3 | 4.67 | 171 |
R Cerebellum | 30 | −63 | −27 | 4.15 | 82 | |
L Cerebellum | −30 | −63 | −30 | 4.03 | 59 | |
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R Inferior Frontal Gyrus | 46/47 | 36 | 33 | 0 | 5.72 | 424 |
R Insula | 47 | 39 | 18 | −6 | 5.31 | |
L SMA/Superior FrontalGyrus | 6 | −9 | 15 | 60 | 5.38 | 694 |
R SMA/Superior FrontalGyrus | 6 | 9 | 9 | 63 | 5.07 | |
R Cerebellum | 3 | −63 | −15 | 5.30 | 324 | |
L Inferior Frontal Gyrus | 45/47 | −36 | 21 | −9 | 5.14 | 783 |
L Insula | 13 | −30 | 24 | 3 | 5.08 | |
L Cerebellum | −33 | −54 | −33 | 4.69 | 67 | |
L Caudate | −15 | −6 | 21 | 4.38 | 63 | |
L Thalamus | −12 | −6 | 9 | 4.20 | ||
R Caudate | 15 | −9 | 21 | 4.36 | 64 | |
R Middle Cingulate Gyrus | 21 | −3 | 36 | 3.89 | ||
L Precuneus | 7 | −6 | −63 | 54 | 3.95 | 72 |
R Precuneus | 7 | 6 | −60 | 60 | 3.66 | 59 |
R Postcentral Gyrus | 5 | 15 | −48 | 72 | 3.44 |
No brain regions were significantly active when comparing “general” vs “personal” within lie condition, whereas “personal” vs ”general” comparison revealed significant activations in the superior and medial frontal regions, the posterior cingulate, precuneus, middle temporal and angular gyri (see
The activations are superimposed on a Colin27 template image in the MNI space. The colored bar represents t-values; L – left side; R- right side.
Brain Region | BA | MNI coordinates | Z-score | Clustersize | ||
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x | y | z | |||
L Precuneus | 7 | −3 | −54 | 36 | 5.29 | 432 |
R Posterior Cingulate Cortex | 31 | 3 | −51 | 27 | 5.05 | |
L Superior Medial Gyrus | 31 | 0 | 57 | 21 | 5.00 | 800 |
R Anterior Cingulate Cortex | 10 | 12 | 48 | 12 | 4.61 | |
R Middle Temporal Gyrus | 21 | 60 | −9 | −21 | 4.18 | 49 |
L Angular Gyrus | 39 | −54 | −63 | 27 | 4.13 | 172 |
R Angular Gyrus | 39 | 57 | −63 | 30 | 4.12 | 70 |
R Middle Temporal Gyrus | 45/46 | 57 | −54 | 18 | 3.17 | |
L Middle Temporal Gyrus | 45/46 | −57 | 0 | −18 | 3.86 | 60 |
To address the question which brain structures are related to deceptive responses in the two sexes, we examined the contrasts: “lie vs. truth” separately in men and women focusing on general information, personal information, and both types of information together.
For both general and personal information, in the two sexes, significant increases in BOLD signal intensity were found in the right inferior frontal gyrus, bilateral caudate, the left thalamus and the right cerebellum. In women, significant activations were additionally found in the right insula and three frontal regions: the left superior frontal gyrus, the left superior medial gyrus, and the right middle frontal gyrus. In men, significant activations were also revealed in the left insula, the right thalamus, and in several frontal, parietal, temporal, and occipital cortical areas including the superior frontal gyrus and the precuneus in the right hemisphere, as well as the middle occipital gyrus, the middle temporal gyrus, the parahippocampal gyrus, the supramarginal gyrus and the precuneus in the left hemisphere (see
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R Superior Frontal Gyrus | 6 | 3 | 12 | 60 | 6.21 | 2606 |
L Inferior Frontal Gyrus | 47 | −39 | 27 | 0 | 5.92 | |
R Cerebelum | 33 | −57 | −33 | 6.00 | 1868 | |
Left Middle Occipital Gyrus | −18 | −96 | 0 | 5.31 | ||
R Inferior Frontal Gyrus | 47 | 39 | 18 | −3 | 5.49 | 406 |
L Middle Temporal Gyrus | 21 | −57 | −39 | −6 | 4.73 | 100 |
L Parahippocampal Gyrus | 19 | −39 | −45 | −3 | 3.21 | |
R Thalamus | 15 | −12 | 15 | 4.52 | 46 | |
R Caudate | 21 | −15 | 27 | 3.72 | ||
Left SupraMarginal Gyrus | 40 | −54 | −48 | 27 | 4.37 | 92 |
L Precuneus | 7 | −6 | −69 | 48 | 4.33 | 60 |
R Precuneus | 7 | 6 | −75 | 57 | 3.90 | |
L Caudate | −15 | −6 | 21 | 4.13 | 47 | |
L Insula | −30 | −6 | 24 | 3.54 | ||
L Thalamus | −3 | −12 | 15 | 4.27 | 72 | |
R Thalamus | 3 | −18 | 12 | 4.26 | ||
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−33 | 24 | 0 | 5.25 | 368 | |
R Inferior Frontal Gyrus | 47 | 33 | 30 | 0 | 5.22 | 209 |
R Caudate | 15 | −9 | 21 | 4.57 | 84 | |
L Superior Frontal Gyrus | 6 | −9 | 21 | 60 | 4.41 | 296 |
L Superior Medial Gyrus | 8 | −3 | 18 | 51 | 4.23 | |
L Thalamus | −12 | −3 | 12 | 4.36 | 61 | |
L Caudate | −15 | 3 | 18 | 4.14 | ||
R Cerebelum | 3 | −60 | −9 | 4.15 | 52 | |
R Middle Frontal Gyrus | 46 | 48 | 27 | 27 | 3.99 | 73 |
For general information, several brain regions were activated in both men and women: the left inferior frontal gyrus, the left insula, the left SMA, the left inferior frontal gyrus, the left superior medial gyrus, and the right cerebellum. Four additional regions were activated in women: the right SMA, the right inferior frontal gyrus, the left occipital gyrus, and the left cerebellum. In men, significant activations were additionally found in four brain areas: the left precentral gyrus, the left middle frontal gyrus, the left middle occipital gyrus, and the right insula. To directly analyze the gender differences in brain activity regarding deception, we compared the contrast “lie vs. truth” between men and women. Neither the comparison of “women vs. men” nor the comparison of “men vs. women” revealed significant suprathreshold clusters (see
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L Insula | 13 | −36 | 21 | 3 | 5.6 | 582.0 |
L Inferior Fronatal Gyrus | 44 | −42 | 12 | 9 | 4.4 | |
L SMA | 6 | 0 | 12 | 57 | 4.3 | 209.0 |
L Cingulate Cortex/Superior Fronatl Gyrus | 32 | −3 | 30 | 33 | 4.3 | |
L Superior Medial Gyrus/Superior Fronatl Gyrus | 32 | −9 | 21 | 42 | 4.1 | |
R Insula | 13 | 42 | 18 | 0 | 4.3 | 74.0 |
L Precentral Gyrus | 6 | −36 | 0 | 51 | 4.2 | 119.0 |
R Cerebellum | 33 | −54 | −33 | 4.2 | 68.0 | |
L Middle Frontal Gyrus | 45/46 | −45 | 18 | 36 | 4.0 | 64.0 |
L Inferior Frontal Gyrus | 46/47 | −45 | 6 | 24 | 3.7 | |
L Middle Occipital Gyrus | 18 | −27 | −99 | −3 | 3.7 | 42.0 |
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R Cerebellum | −3 | −75 | −27 | 4.78 | 80 | |
L Cerebellum | −15 | −72 | −33 | 4.38 | ||
R SMA | 6 | 9 | 12 | 66 | 4.74 | 82 |
L SMA | 6 | −3 | 18 | 60 | 4.07 | |
L Inferior Fronatal Gyrus | −39 | 27 | −3 | 3.37 | ||
L Insula | 13 | −30 | 18 | −12 | 3.25 | |
L Occipital Gyrus | 46/47 | −12 | −96 | −6 | 4.15 | 60 |
R Inferior Frontal Gyrus | 45/46 | 48 | 27 | 30 | 4.09 | 70 |
L Superior Medial Gyrus | 8 | −3 | 27 | 45 | 4.01 | 44 |
R Cingulate Cortex | 32 | 6 | 21 | 39 | 3.14 | |
L Inferior Frontal Gyrus | 45/46 | −39 | 12 | 24 | 3.87 | 57 |
For personal information,
The bar chart represents the mean contrast value of the cluster. The activation is superimposed on a Colin27 template image in the MNI space. The colored bar represents t-values; L – left side; R- right side.
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R SMA/Superior Frontal Gyrus | 6 | 9 | 9 | 63 | 5.14 | 561 |
L SMA/Superior Frontal Gyrus | 6 | −6 | 12 | 51 | 4.75 | |
L Middle Frontal Gyrus | 45/46 | −36 | 39 | 18 | 5.08 | 721 |
L Inferior Frontal Gyrus | 45 | −51 | 15 | 3 | 4.89 | |
R Inferior Frontal Gyrus | 47 | 39 | 33 | 0 | 5.06 | 291 |
R Insula | 13 | 39 | 18 | −3 | 4.72 | |
R Cerebellum | 6 | −5 | −12 | 4.97 | 583 | |
L Caudate | −21 | −9 | 27 | 4.80 | 36 | |
R Middle Frontal Gyrus | 46 | 30 | 39 | 21 | 4.60 | 70 |
L Superior Frontal Gyrus | 6 | −27 | −3 | 66 | 3.97 | 57 |
L Precentral Gyrus | 6 | −36 | −3 | 66 | 3.47 | |
L Thalamus | −3 | −2 | 12 | 3.88 | 38 | |
L Calcarine Sulcus | 17 | −12 | −7 | 9 | 3.51 | 44 |
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R Inferior Frontal Gyrus | 47 | 36 | 33 | 0 | 4.38 | 55 |
R Insula | 13 | 27 | 24 | −3 | 4.14 | |
L Inferior Frontal Gyrus | 47/45 | −36 | 24 | −12 | 3.99 | 109 |
In the present study, we aimed to investigate whether men and women differ when falsifying general (self-irrelevant) and personal (self-relevant) information. As for the behavioral performance, men and women did not differ when it came to accuracy or RTs. The only difference was observed in differential RTs (i.e., the differences between lying and truth telling). In men, differential RTs for personal information were significantly longer than for general information. No such differences were observed in women. This may potentially suggest that for men lying about personal information is more difficult and produces a more significant interference effect than does lying about general information, whereas for women both types of lying have similar levels of difficulty. In agreement with this hypothesis, we found differences in neural correlates underlying deceptive responses between men and women significant only in case of personal information.
In line with previous studies, both groups showed deception-related activations in a number of regions. We found both common and unique neural correlates that underlied falsifying self-irrelevant and self-relevant information. A functional overlap between these two types of lying (including the bilateral prefrontal areas of the inferior frontal gyrus and the superior frontal gyrus/supplementary motor area, as well as bilateral cerebellum, the left insula and the right caudate) bears resemblance to brain areas that generally contribute to executive control (e.g.
In men and women falsifying non-autobiographical responses recruited similar brain areas. A direct between group contrast revealed no areas of activity that would differ between men and women. In contrast, when the two sexes were directly compared for activations during falsifying autobiographical information, women revealed no areas of significantly higher activation than men, whereas men showed higher BOLD signal compared to women in the left middle frontal gyrus (MFG). Changes in the activity of the left MFG were shown to be associated with the generation of deceptive responses in healthy individuals
Finally, we examined the relationship between the sex related brain activity differences and subjective scores of masculinity and femininity from the Gender Identity Inventory and found no such association. If we assume that the Gender Identity Inventory measures how well one can fit into the traditional gender roles, the sex differences in brain activation as found in the present study are unlikely to be influenced by differential socialization in men and women.
In conclusion, to our knowledge, this is the first fMRI study that reports gender differences in the neural correlates of deception. We provide evidence that despite comparable performance and brain activity on the deception task related to general information, there are sex differences in brain activity when falsifying personal information. We observed overall enhanced activation in men, particularly in the left middle frontal gyrus. This may suggest that men found the personal deception task more difficult to perform, probably due to less efficient mechanisms for selecting relevant information in the pursuit of a behavioral goal. Therefore, the results support the idea of studying men and women as distinct groups in functional imaging studies on deception. However, the interpretation of this study is limited by the low ecological validity of the experimental paradigm. The participants were instructed to make deceptive responses, which may not be equivalent to deception during real life conditions or even in computerized games (see
The Bioethics Committee of Warsaw Medical University approved the experimental protocol, and informed written consent was obtained from all subjects prior to the study.
Twenty-nine right-handed and healthy volunteers (15 female and 14 male) between the ages of 21 and 28 participated in this study (female mean age = 23.7; SD = 2, male mean age = 24.9; SD = 2.3). Study groups were balanced in years and type of education (female mean years of education = 16.07; SD = 1.64, male mean years of education = 16.73; SD = 1.85; mostly biology and psychology students or graduates). Right-handedness was confirmed using the Edinburgh Inventory
All subjects underwent the same experimental procedure. First, they completed a paper-pencil questionnaire concerning personal information and general knowledge. On the following day, they underwent an fMRI scan during which they answered questions that were prepared based on the information obtained from the questionnaire. There were 120 questions in total: 60 personal and 60 general. Out of each 60 questions 30 were presented with the instruction to give a false reply and 30 with the instruction to tell the truth. Two types of answers were possible for each category of questions: 15 were supposed to be answered with a “Yes” and 15 with a “No”. All experimental conditions were fully counterbalanced with respect to the instruction, type of question and type of answer. The questions were presented in a pseudo random order identical for every subject. The questions were kept as simple and as short as possible. The average length (5.2 words) was also matched across conditions.
Each trial started with a centrally presented fixation point with the instruction (to lie or to tell the truth) being presented above the fixation which, after 2 seconds, was followed by a question being displayed for 3 seconds at the center of the fixation point. The instruction was displayed throughout the entire duration of the trial (
The instruction was presented above the fixation point and, after 2 seconds, was followed by a question that appeared below the fixation point for 3 seconds. The inter-stimulus interval was varied from 8–12 s (for details see text).
As the motivation to lie is rather low in laboratory studies, we sought to increase the subjects’ motivation as follows: (1) Our recent studies have shown that monetary rewards motivated healthy subjects to perform better
Whole brain imaging was performed with a 1.5-Tesla MRI scanner (Magnetom Avanto; Siemens, Erlangen, Germany) equipped with 32-channel phased array head coil. Head movements were minimized with cushions placed around the participants’ heads. A T2*-weighted echo planar imaging (EPI) sequence was used for functional imaging with the following parameters: time repetition = 2000 ms; time echo = 50 ms; flip angle = 90 deg; inplane resolution = 2.5×2.5 mm; field of view = 240 mm; and 23 axial slices, with 6 mm slice thickness and no gap between slices. For each subject, the functional run consisted of 915 volumes lasting 30 minutes and 30 seconds. Detailed anatomical data of the brain were acquired with sagittal T1-weighted (time repetition = 1720 ms; time echo = 2.92 ms) and T2-weighted (TR = 3200 ms; TE = 381 ms) MPRAGE sequences with isotropic voxel size (1×1×1 mm).
Statistical Parametric Mapping (SPM8, Wellcome Trust Center for Neuroimaging, London, UK) running on MATLAB 7.9 (The Math-Works Inc. Natick, MA, USA) was used for data processing and statistical analyses. Images were corrected for head movement (spatial realignment). Slice acquisition time was corrected by taking the middle slice in time as a reference. Both anatomical scans were coregistered with the mean of realigned functional images. The upgraded implementation of unified segmentation (“New Segment”) was used to segment anatomical images into grey matter, white matter and other tissues. Data from both the T1- and T2-weighted scans of the same subject were used to obtain more accurate results. High-dimensional Diffeomorphic Anatomical Registration Through Exponentiated Lie Algebra (DARTEL,
In the first-level statistical analysis, experimental stimuli were split into separate regressors based on the instruction-answer scheme. Misses and incorrect responses were entered as a separate regressor and excluded from further analysis. Head movement parameters were also entered as covariates into the design matrix. Each stimulus was modeled as an event of 3 s duration, starting when the question was presented and ending when it disappeared from the screen. All stimulus functions were convolved with the canonical HRF basis function. In a second-level group random effects analysis, linear contrasts of the parameter estimates were subjected to one-sample t-tests. Anatomical labels were assigned to functional activations using a probabilistic cytoarchitectonic map
We are grateful to Richard Stanislaus Frackowiak for his helpful comments on the paper. and to Małgorzata Zarzycka and Dagmara Bartczak for subject recruitment.