Article Figures & Data
Figures
- Figure 1.
Task design. In the fMRI scanner, participants viewed face pairs from different races (Black, White) and genders (women, men) and decided if the two faces belonged to the same individual. Participants saw each face for 600 ms and responded when the second face was on screen. Faces were presented with a random horizontal jitter to prevent low-level suppression effects. The design included three face pair conditions for each combination of race and gender. Participants saw (A) a face followed by a scrambled visual patch in the shape of a face in the single condition (i.e., baseline trials; we included this condition only in experiment 2), (B) a face followed by the same face in the repeated-face condition, and (C) a face followed by a different face (matched in gender and race) in the different-face condition. We report the behavioral results in Figure 2 (male targets) and Extended Data Figure 1-1 (female targets).
- Figure 2.
Reaction time and memory performance for male faces in experiments 1 and 2. All panels depict estimates computed by gLMMs, as detailed in Materials and Methods. A, In the face repetition task in experiment 1, participants responded faster to repeated faces (t = 11.33, p < 0.001). This effect was qualified by an interaction with race, such that participants responded faster to different White individuals compared with different Black individuals (for inferential statistics, see main text). B, In a two-alternative forced-choice test, participants in experiment 1 indicated their memory by selecting the individual they thought was presented in the face repetition task. All trials included one previously presented individual (“old”) and one never-before-seen individual (“new”). Participants remembered old White targets better than old Black targets (OR = 1.16, Wald’s z = 3.005, p = 0.003). We did not observe a significant effect of type of repetition on memory (OR = 1.07, Wald’s z = 1.48, p = 0.14) or of the interaction of repetition with race (OR = 1.05, Wald’s z = 1.09, p = 0.28). C, Experiment 2 included an additional condition, single faces, to facilitate comparison of repetition suppression to baseline neural activity for each race. Race did not affect reaction time in the single-face condition (t = 1.04, p = 0.300). When analyzing only face-pair trials (omitting the single face trials), participants responded faster to repeated faces (t = 2.46, p = 0.014), an effect that was qualified by an interaction, replicating the results of experiment 1 (interaction model comparison: χ(1) = 15.095, p < 0.001): participants were slower to respond to different Black faces compared with different White faces (t = 2.48, p = 0.013). Unexpectedly, participants in experiment 2 were also slower to respond to repeated White faces compared with repeated Black faces (t = 3.29, p < 0.001). Note that unlike experiment 1, the correct response key in experiment 2 was imbalanced between the conditions; we assigned the same key to single and different conditions to simplify the task, hence assigning the same correct response key to two thirds of the trials. This design choice probably slowed the responses to repeated trials, as participants had to use an infrequent key to respond correctly to these trials. This, in turn, might have made responses to repeated targets more difficult, a difficulty that manifested particularly strongly for White targets. Error bars indicate standard error of the mean.
- Figure 3.
Results of the dynamic face localizer task and repetition suppression parameter estimates extracted from the FFA. A, The spatial extent of the key ROIs of interest, the FFA, and the OFA, presented as degree of spatial overlap between participants in normalized space. We generated these ROIs with the group-constrained subject-specific (GcSS) approach (Julian et al., 2012) for the contrast of faces > other categories at the level of each individual participant. For a table listing the full ROI list, see Extended Data Figure 3-6. B, Repetition suppression parameter estimates in the FFA for different-face and repeated-face pairs for Black and White male faces. Upper panel: to present repetition suppression effects, we subtracted neural activity in response to single faces (baseline) from the neural response to the different conditions (differ, repeat), separately for each race (Black, White). Negative values indicate neural suppression compared with baseline. Across all figures, individual dots represent neural suppression for unique participants. Each figure also visualizes the mean of each condition (as a red dot), the median (solid horizontal line), and first and third quartiles (boxplot). Lower panel: mean effect size (the difference in suppression effect) and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. The results demonstrate more release from suppression (i.e., less negative values) for different White targets compared with different Black targets, but no difference in suppression for repeating Black and White targets. This pattern suggests that the FFA forms unique representations for different individuals, but only for members of one’s own racial group. We report the results of the parallel analysis in the OFA and visual cortex in Figure 4. Extended Data Figure Figures 3-1, 3-2, 3-3, 3-4 demonstrate the robustness of the effect to different analytic strategies. In Extended Data Figure 3-5, we report the results of the main analysis with female faces.
- Figure 4.
Repetition suppression results for repeated and different Black and White targets for the OFA and primary visual cortex (for additional details on analysis approach, see Materials and Methods). Similar to Figure 3B, negative values indicate neural suppression compared with baseline. The lower panel depicts effect size estimate (the difference in suppression effect) and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. A, The OFA demonstrated robust repetition suppression for repeated and different faces (F(1,28) = 245.88, MSE = 12.06, p < 0.001, η2p = 0.90 and F(1,28) = 247.03, MSE = 10.13, p < 0.001, η2p = 0.90 for repeated and different targets, respectively). The OFA showed some release from suppression for different faces (F(1,28) = 9.93, MSE = 1.98, p = 0.004, η2p = 0.26), but we found no indication for an effect of race on suppression for repeated or different targets (F(1,28) = 0.04, MSE = 3.88, p = 0.85, η2p = 0.001 and F(1,28) = 0.46, MSE = 3.62, p = 0.50, η2p = 0.02, respectively). Thus, the OFA was not sensitive to the group features of the different faces. B, Primary visual cortex (including V1) served as a control condition. No effects were observed in this region (all Fs < 1.4, all ps > 0.2).
Extended Data
Extended Data Figure 1-1
Reaction time and memory performance for female faces in experiments 1 and 2. All panels depict estimates computed by gLMMs, as detailed in Materials and Methods. A, Participants in experiment 1 were faster to respond to repeated faces than to different faces (t = 8.43, p < 0.001). However, unlike responses for male faces, there was no evidence for an effect of race (t = 0.34, p = 0.74) nor for an interaction of race with type of repetition (interaction model comparison: χ(1) = 1.93, p = 0.16, suggesting that a model with no interaction term provides a better fit to the data). This pattern hints that Black female faces were individuated to the same extent as White female faces. When we included all trials to test a full model of the data, with the fixed effects of race, repetition, and gender, we observed a significant three-way interaction (model comparison: χ(4) = 10.67, p = 0.031), confirming the difference in individuation between male and female faces. B, Unlike male faces, participants were not more likely to remember White female faces compared to Black female faces (OR = 1.004, Wald’s z = 0.09, p = 0.93). Participants were more likely to remember repeated faces compared to different faces (OR = 1.10, Wald’s z = 2.20, p = 0.028) with no interaction with race (OR = 1.02, Wald’s z = 0.456, p = 0.65). However, we did not observe a statistically significant three-way interaction effect for gender when it was inserted into the model (χ(4) = 6.88, p = 0.14). C, Similar to responses to male faces, participants in experiment 2 responded faster to single face trials (model comparison: χ(2) = 111.42, p < 0.001). However, unlike response times for male faces, we did not observe a robust effect of race (t = 1.97, p = 0.049) nor an interaction of race and repetition (model comparison: χ(2) = 1.03, p = 0.597; we obtained similar results when omitting the single condition from the analysis). As in experiment 1, when we included the fixed effects of race, repetition, and gender in the model, we observed a significant triple interaction (model comparison: χ(4) = 27.84, p < 0.001), once again confirming the difference in processing between male and female faces. Error bars indicate SEM. Download Figure 1-1, TIF file.
Extended Data Figure 3-1
Repetition suppression parameter estimates for the FFA, OFA, and primary visual cortex for analyses including participants we excluded in the main text (N = 32). Upper panel, Repetition effects for all individuals. Lower panel, Effect size estimate and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. Overall, results replicate with this sample (compare to Figs. 3B, 4). A, FFA results. Activation in FFA was suppressed to nearly an equivalent degree for both Black and White repeated targets [repetition effect: F(1,31) = 167.86, MSE = 5.32, p < 0.001, η2p = 0.84; interaction effect: F(1,31 = 1.50, MSE = 0.98, p = 0.23, η2p = 0.05; equivalence test for the two repetition effects (mean difference: 0.43): p = 0.056, equivalence interval (–1.02, 0.16)]. FFA also showed more release from suppression for White targets than for Black targets (F(1,31) = 11.96, MSE = 0.56, p = 0.002, η2p = 0.31; interaction between repeated and different faces: F(1,31) = 3.35, MSE = 0.57, p = 0.08, η2p = 0.10). And again, similar to the main findings, we observed statistically equivalent levels of repetition suppression for different and repeated Black targets [equivalence test (mean difference: 0.46): p = 0.005, (–0.80, –0.12)]. B, The OFA demonstrated robust repetition suppression for repeated and different faces (F(1,31) = 273.17, MSE = 11.83, p < 0.001, η2p = 0.90 and F(1,31) = 261.09, MSE = 10.37, p < 0.001, η2p = 0.89 for repeated and different trials, respectively). The OFA showed some release from suppression for different faces (F(1,31) = 12.43, MSE = 1.87, p = 0.001, η2p = 0.29), but no indication for an effect of race on any of these results (F(1,31) = 0.05, MSE = 3.59, p = 0.83, η2p = 0.002 and F(1,31) = 0.28, MSE = 3.39, p = 0.50, η2p = 0.009 for repeated and different targets, respectively). Thus, the OFA was not sensitive to the group features of the different faces. C, We did not observe any effects in the primary visual cortex, again replicating the principal analysis (all Fs < 2.02, all ps > 0.17). Download Figure 3-1, TIF file.
Extended Data Figure 3-2
Repetition suppression parameter estimates for the FFA, OFA, and primary visual cortex for analyses excluding targets that participants incorrectly classified (preregistered complementary analysis; N = 29). Upper panel, Repetition effects for all individuals. Lower panel, Effect size estimate and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. As with the previous analysis, results replicate the main findings. A, FFA results. Activation in FFA was suppressed to nearly an equivalent degree for both Black and White repeated faces [repetition effect: F(1,28) = 180.11, MSE = 4.56, p < 0.001, η2p = 0.87; interaction effect: F(1,28) = 0.28, MSE = 1.60, p = 0.60, η2p = 0.01; equivalence test for the two repetition effects (mean difference: 0.25): p = 0.0598, equivalence interval (–1.05, 0.55)]. FFA also showed more release from suppression for White targets than for Black targets (F(1,28) = 6.94, MSE = 0.60, p = 0.01, η2p = 0.20; interaction between repeated and different faces: F(1,28) = 2.01, MSE = 0.94, p = 0.17, η2p = 0.07]. And again, similar to the main findings, we observed statistically equivalent levels of repetition suppression for different and repeated Black targets [equivalence test (mean difference: 0.47): p = 0.036, (–0.95, 0.02)]. B, The OFA demonstrated robust repetition suppression for repeated and different faces (F(1,28) = 233.52, MSE = 12.73, p < 0.001, η2p = 0.89 and F(1,28) = 267.83, MSE = 9.52, p < 0.001, η2p = 0.91 for repeated and different trials, respectively). The OFA showed some release from suppression for different faces (F(1,28) = 4.70, MSE = 3.46, p = 0.04, η2p = 0.14). As before, race did not interact with suppression for repeated or different faces (F(1,28) = 0.99, MSE = 7.52, p = 0.33, η2p = 0.03 and F(1,28) = 0.08, MSE = 4.51, p = 0.78, η2p = 0.003 for repeated and different targets, respectively). Thus, once again, the OFA was not sensitive to the group features of the different faces. C, We did not observe any effects in the primary visual cortex, again replicating the principal analysis (all Fs < 1.13, all ps > 0.30). Download Figure 3-2, TIF file.
Extended Data Figure 3-3
Parameter estimates for the FFA, OFA, and primary visual cortex for the original preregistered analysis, in which we erroneously modelled single target trials with variable durations based on participants’ reaction time to the scrambled image that followed the single face (N = 29). Upper panel, Repetition effects for all individuals. Lower panel, Effect size estimate and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. As in all previous analyses, we plot neural activity by subtracting the response to single faces (baseline) from the neural response to the different conditions (different, repeated), separately for each race (Black, White). Parameter estimates in this analysis are positive and no longer reflect suppression, as the baseline in this analysis reflects the neural activity in response to the scrambled image, rather than an actual face. This response was naturally weaker in face-sensitive regions. Nonetheless, overall pattern of results replicated the principal analysis. A, FFA results. Activation was different from baseline to an equivalent degree for Black and White repeated faces [repetition effect: F(1,28) = 51.79, MSE = 0.35, p < 0.001, η2p = 0.65; interaction effect: F(1,28) = 0.15, MSE = 0.50, p = 0.70, η2p = 0.005; equivalence test for the two repetition effects (mean difference: 0.10): p = 0.001, equivalence interval (–0.55, 0.34)]. FFA also showed more difference from baseline for White targets than for Black targets (F(1,28) = 6.74, MSE = 0.31, p = 0.01, η2p = 0.19; interaction between repeated and different faces: F(1,28) = 3.65, MSE = 0.38, p = 0.07, η2p = 0.12). And again, similar to the main findings, we observed statistically equivalent levels of difference from baseline for different and repeated Black targets [equivalence test (mean difference: 0.28): p < 0.001, (–0.55, –0.003)]. B, The OFA demonstrated difference from baseline only for different and not for repeated faces (F(1,28) = 2.48, MSE = 1.48, p = 0.13, η2p = 0.08 and F(1,28) = 28.66, MSE = 1.26, p < 0.001, η2p = 0.51 for repeated and different trials, respectively). The difference between OFA response to different and repeated faces was significant (F(1,28) = 8.67, MSE = 1.94, p = 0.006, η2p = 0.24). As before, race did not interact with difference from baseline for repeated or different faces (F(1,28) = 0.55, MSE = 1.42, p = 0.47, η2p = 0.02 and F(1,28) = 0.99, MSE = 1.26, p = 0.33, η2p = 0.03, respectively). Thus, the OFA was not sensitive to the group features of the different faces. C, We did not observe any effects of race or interaction with race in the primary visual cortex, again replicating the principal analysis (all Fs < 2.13, all ps > 0.16). Download Figure 3-3, TIF file.
Extended Data Figure 3-4
Parameter estimates in the (A) FFA and (B) OFA for the three experimental conditions for Black and White male faces (without correcting for differences in baseline activity). Upper panels, Neural activity in response to the different conditions (single, different, repeated), separately for each race (Black, White). Individual dots represent neural activity for unique participants. Vertical lines (presented in parallel to the scatter plot) depict the mean and SD for each condition. Lower panel, Mean effect size (the repetition suppression effect) and the bootstrapped 95% confidence intervals for the comparison between type of repetition and single-face targets for each race. For statistical analyses, see Figure 3 and main text. Download Figure 3-4, TIF file.
Extended Data Figure 3-5
Repetition suppression results for female targets for the FFA, OFA, and primary visual cortex using the analysis reported in the main manuscript (compare to results for male targets in Figs. 3B, 4). We subtracted neural activity in response to single faces (baseline) from the neural response to the different conditions (different, repeated), separately for each race (Black, White; upper panel). The lower panel depicts effect size estimate (the difference in suppression effect) and the bootstrapped 95% confidence intervals for the comparison between Black and White targets in each condition. A, The FFA demonstrated robust repetition suppression for repeated and different faces (F(1,28) = 392.66, MSE = 2.48, p < 0.001, η2p = 0.93 and F(1,28) = 290.91, MSE = 2.66, p < 0.001, η2p = 0.91 for repeated and different trials, respectively). The FFA also demonstrated release from suppression for different faces (F(1,28) = 14.66, MSE = 0.78, p < 0.001, η2p = 0.34), an effect that was qualified by an interaction with race (F(1,28) = 6.76, MSE = 0.38, p = 0.01, η2p = 0.19). However, the FFA did not show significant simple effects (i.e., differences in suppression) between Black and White female targets (F(1,28) = 2.41, MSE = 1.58, p = 0.13, η2p = 0.08 and F(1,28) = 0.08, MSE = 1.51, p = 0.77, η2p = 0.003 for repeated and different faces, respectively). As we did not have an a priori hypothesis for female targets, we cannot offer a reliable interpretation of these results. B, Much like for male targets, the OFA demonstrated robust repetition suppression for repeated and different faces (F(1,28) = 517.23, MSE = 6.92, p < 0.001, η2p = 0.95 and F(1,28) = 371.93, MSE = 8.28, p < 0.001, η2p = 0.93 for repeated and different trials, respectively). The OFA showed some release from suppression for different faces (F(1,28) = 6.70, MSE = 2.79, p = 0.02, η2p = 0.19), but no indication of an effect of race on any of these results (F(1,28) = 3.25, MSE = 4.84, p = 0.08, η2p = 0.10 and F(1,28) = 2.08, MSE = 4.71, p = 0.16, η2p = 0.07 for repeated and different targets). Thus, as for male targets, the OFA was not sensitive to the group features of the different female faces. C, Primary visual cortex (including V1) results. No effects were observed in this region (all Fs < 1.2, all ps > 0.2). Overall, we did not observe any neural evidence for the outgroup homogeneity effect for female targets, paralleling the behavioral results. Download Figure 3-5, TIF file.
Extended Data Figure 3-6
Results from the main functional ROI analysis [group-constrained subject-specific (GcSS); see Materials and Methods]. For each ROI, the GcSS algorithm defines a parcel to intersect with activation for each individual participant, thus reliably identifying the same functional ROIs in all participants. We conducted the GcSS analyses with the contrast of faces > other categories in independent localizer scans. A priori ROIs are presented in italics. Download Figure 3-6, DOCX file.
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