Study 1: simulated voting
In the first study, participants voted in a simulated election. Participants viewed grayscale pictures of 100 pairs of unfamiliar real politicians, one Republican and one Democrat, who competed in the 2006 U.S. midterm elections (A; see Methods for details). Participants saw the image of each of the two candidates in sequence, for only 1 s, separated by a blank screen, and after a delay were asked to cast their vote. All the data were collected before the 2006 election, ensuring that participants could not have been influenced in any way by the real election outcomes.
Fig. 1 Trial design of the two studies. Each experiment showed participants grayscale images of real politicians, one at a time, separated by a variable interstimulus interval. For both experiments, stimuli are depicted as they appeared on the screen. (A) Study (more ...)
In order to increase the sensitivity of our fMRI analyses, we limited our analyses to voxels within brain areas already known to be associated with the evaluation of facial appearance and affective processing. We produced region of interest (ROI) masks using the Automated Anatomical Labeling Toolbox for SPM (Tzourio-Mazoyer et al.
). These ROIs are as follows: (i) the bilateral temporal lobes, including the fusiform gyrus (associated with gaze and face processing; Kanwisher and Yovel, 2006
); (ii) the bilateral caudate (associated with positive evaluation of faces; Kim et al.
); (iii) the bilateral putamen (associated with reward-based processing; O’Doherty et al.
); (iv) the bilateral gyrus rectus (associated with positive evaluation of faces; Kim et al.
); (v) the bilateral orbitofrontal cortex (associated with positive evaluation of faces; Gottfried et al.
; Kim et al.
); (vi) the bilateral insula [associated with perception of lack of trustworthiness (Winston et al.
), and pain perception (Ploghaus et al.
; Salomons et al.
), but also with positive evaluation of faces (Kim et al.
)]; (vii) the bilateral amygdala (associated mostly with negative facial attribution; Winston et al.
); and (viii) the bilateral anterior cingulate (associated with social rejection; Eisenberger et al.
; Somerville et al.
). We report only those clusters surviving FWE correction at P
< 0.05, as determined by Monte Carlo simulation using AlphaSim in AFNI (Xiong et al.
; Cox, 1996
) (see Supporting Information).
We analyzed the fMRI data for this first study by using the voting data provided by the participants in our experiment. We estimated a general linear model in which the appearance of an individual candidate's image was modulated by its vote share in the simulated election, a variable that we refer to as lab vote share (see Methods for details). We found that positive lab vote share elicited no significant activation in any ROIs. In fact, positive lab vote share did not result in any significant activation anywhere, even with a whole-brain analysis. In contrast, negative lab vote share (i.e. election loss) elicited robust, statistically significant activations in bilateral insula [222 voxels (48, −3, −9), Z
= 3.81; 179 voxels (−45, 12, 9); Z
= 3.96; Supporting Information Table S1
; A], and bilateral anterior cingulate cortex [239 voxels (3, 33, 9), Z
= 3.73; Supporting Information Table S1
; A]. Thus, these regions are increasingly engaged by viewing candidates with larger margins of electoral loss.
Fig. 2 Activation in the insula/parainsula correlates with election loss in both studies. (A) Study 1: activation during the simulated voting study in bilateral insula [blue circles; left insula (−45, 12, 9) and right insula (48, −3, −9)] (more ...)
Fig. 3 Activation in ventral anterior cingulate cortex correlates with election loss in both studies. (A) Study 1: activation during the simulated voting study in bilateral anterior cingulate [blue circle; (3, 33, 9) and (−9, 21, 24)] was negatively (more ...)
The lack of any significant brain activations elicited by viewing winners in our simulated vote, coupled with the robust activations elicited by viewing losers, suggests that negative attributions from appearance may play a predominant role in mediating how appearance influences voting.
Study 2: candidate trait judgments
In our second study, we sought to further investigate the relative contributions to this effect made by positive and negative attributions (which might be either implicit or explicit), as well as the underlying neural structures we had found in the first study. In order to selectively enhance processing of one attribution over another, we asked participants to make overt judgments in the scanner. To best investigate the effects of candidate appearance alone, we maximized thin-slice conditions with a rapid stimulus presentation. We used a subset of the same images previously shown to elicit an association between real-electoral outcome and judgments of competence (Todorov et al.
Study participants made social judgments based on the images of real, but unfamiliar, political candidates who ran against one another in the 2000, 2002 and 2004 U.S. Congressional elections, mainly in the House of Representatives. Participants made binary judgments about 30 pairs of candidates, one Republican and one Democrat (in randomized order), on two putatively positive traits, attractiveness (Attr) and competence (Comp), and two putatively negative traits, public deceitfulness (Dect) and personal threat (Thrt), in four separate scanning sessions (see Methods). Each trial consisted of a protocol that has been previously used to investigate face preferences (Kim et al.
), in which the two images in a pair of candidates were presented sequentially, for only 30 ms each (unmasked), one alternating with the other, until the participant pushed a button to indicate which of the two faces showed more of the trait being judged (B).
As one would expect if participants made meaningful judgments, positive trait judgments were positively correlated (Attr and Comp, r = 0.39, P = 0.002), those for negative traits were positively correlated (Thrt and Dect, r = 0.61, P < 0.0001) and those between Comp and Thrt were negatively correlated (Comp and Thrt, r = −0.39, P = 0.002). No other statistically reliable relationships were seen in the behavioral data alone.
The relationship between our behavioral data regarding competence judgments and real-world electoral outcome was in line with the published findings we reviewed above (Todorov et al.
; Ballew and Todorov, 2007
): we found that our participants were above chance in judging winners of real elections as more competent [55 ± 9%, t
(15) = 2.15, P
< 0.05], with the same average individual accuracy as seen in the prior studies. When we examined the majority group competence judgments, comparing candidates who were characterized as competent by a majority of our participants with those who had won elections, the association trended positively [55%, χ2
(1) = 1.00, P
> 0.1, against an expected 50%] but did not reach statistical significance. This is likely due to our fMRI-scale sample size, as sample sizes of 40 or more are generally required to achieve reliability on this particular measure for competence judgments (Todorov et al.
Consistent with the robust effect of election loss we found in our first study, a novel behavioral finding from the second study was that the strongest association between election outcome and trait judgments was seen for personal threat judgments. Majority group personal threat judgments corresponded to election loss 65% of the time [χ2(1) = 9.00, P < 0.05], and average individual accuracy was also above chance [57 ± 10%, t(15) = 2.65, P < 0.05]. In fact, the association between majority personal threat judgments and election outcome was stronger than that for competence [χ2(1) = 4.04, P < 0.05] and public deceitfulness [χ2(1) = 9.00, P < 0.05], although not reliably different from attractiveness [χ2(1) = 2.01, P > 0.1]. In addition, only the association between personal threat judgments and election loss survived in a multiple binomial regression model relating all four social judgments to the election outcomes (beta = 1.5, P = 0.03, r2 = 0.1, P = 0.01).
As previously reported (Todorov et al.
), the association between election outcome and attractiveness judgments was not statistically different from chance for the average individual [46 ± 10%, t
(15) = −1.46, P
> 0.1] or for majority group judgments [58% correspondence with election loss, χ2
(1) = 2.56, P
> 0.1]. Judgments of public deceitfulness across individuals [49 ± 9%, t
(15) = −0.34, P
> 0.1] and group majority judgments [50%, (χ2
(1) = 0, P
> 0.1] also did not differ from chance in associating with election outcome.
Our behavioral findings from the second study are, thus, consistent with what we inferred from our first study: there appears to be a primary role for negative attributions in mediating the effect of candidate appearance on election outcome. Interestingly, this may be especially the case for attributions that affect one's personal welfare (i.e. the personal threat judgments viewers made). Given these behavioral findings, and given that our first study revealed no activations for winners, we focus subsequent imaging analyses on the condition of personal threat (see Supporting Information for more detail). This allows us to determine if loser-elicited activations seen in our first study are also seen here for candidates who lost real elections, under conditions where we aimed to most enhance negative attribution (i.e. in judging personal threat from a smiling politician).
We analyzed the fMRI data from our second study by estimating a general linear model in which separate regressors were formed for the first onset of images based on whether those candidates had won or lost in real elections and on whether those candidates were the majority choice with respect to reflecting a particular trait (see Methods for details). We contrasted the parameter estimates obtained in response to the pictures of candidates who had won and those who had lost real elections. We report significant activations surviving FWE-corrected thresholding at P < 0.05 (see Supporting Information).
Again consistent with Study 1, we found no significant activations in our regions of interest for candidates who won real elections (see Supporting Information for complete details). Instead, we found that candidates who lost real elections, compared to those who won, elicited greater activation in the insula/parainsula [18 voxels (45, 0, −15), t = 4.80; B and C; Table S2B.] and in the ventral anterior cingulate cortex [24 voxels (15, 39, 0); t = 4.02; (9,45,6), t = 3.90; B; Table S2B.]. These locations are within the regions we found for Study 1 and further support the idea that negative attribution is primary in mediating the effects of candidate appearance on voter decisions, and itself is mediated by a network of structures that include the insula/parainsula and ventral anterior cingulate regions. Further evidence for this interpretation comes from the observation that losers elicited an increase in activation in the insula, while winners elicited a decrease (C).
To link our two studies directly, we first chose a region in the right insula from Study 1 (with simulated voting) and queried this region [a 10 mm radius sphere centered on the peak voxel (48, −3, −9)] with respect to the contrast effects seen in Study 2 (with real voting). Consistent with Study 1, we found in Study 2 that the contrast of loser > winner, under the condition of threat judgment, resulted in a significantly enhanced activation in this region [t(15) = 1.87, P < 0.05; D]. However, we found no significant effect under any of the other judgment conditions (P > 0.1). Similarly, we chose a region in the right anterior cingulate from Study 1 and queried this region [a 10 mm radius sphere centered on the peak voxel (3, 33, 9)] with respect to the contrast effects seen in Study 2. Again, we found that the contrast of loser > winner resulted in a significantly enhanced activation in the region, for threat judgment only [t(15) = 1.98, P < 0.05; C; all other conditions, P > 0.1, except for attractiveness, which shows a near-significant effect of winner > loser, t(15) = 1.71, P = 0.054]. Thus, brain regions identified in Study 1 showing a differential sensitivity for images of election losers, compared to winners, show this same sensitivity in Study 2 under conditions in which negative attributions are putatively enhanced, and this time for real election outcomes. This is further evidence that negative attributions are primary in mediating the effect of appearance on voting.
While analyses in Study 2 focused primarily on the threat judgment condition, it is important to note that we observed activations under the other three conditions also (see Supporting Information for details). The direction of the significant election contrasts (loser > winner, or winner > loser) was in line with what one would expect given the valence of the social judgment condition. Thus, both threat and deceit conditions produced activations primarily for loser > winner, whereas attractiveness and competence conditions produced activations primarily for winner > loser. We interpret these data to show that either positive or negative attributions can be enhanced with a sufficiently valenced social judgment context, while negative attributions are primary under the context of voting, particularly when there is a lack of other information about the candidates.