4.1.2. Design

We manipulated Video Version between subjects, showing each subject one of three versions of the event. In addition, subjects assigned themselves into one of three Political Affiliation categories.

#### 4.1.3. Materials and Procedure

As a cover story, we told subjects the study was examining visual and verbal learning styles. Then, we asked subjects to watch a brief video of an interaction between a journalist and a White House intern during a press conference, randomly assigning them to see one of three versions of this event. We collected these data approximately six months after the event occurred. Subjects then made several ratings related to the depicted interaction, to gauge how they interpreted the journalist's behavior.

**Video Versions.** The video versions were as follows. The "altered" version of the video is that tweeted by the then-Press Secretary. It is a 15 s clip with no audio that loops the brief interaction between the journalist and the White House intern a total of six times; on the second loop, and again on the third loop, the video zooms in and it remains zoomed in thereafter. From the original CSPAN footage, we created two additional versions, each 15 s long with the audio removed. Our "looped" version of the video consists of the brief interaction, looped. The "original" version of the video consists of the interaction itself, as well as approximately 6 s of footage preceding the interaction and 6 s of footage following it. Links to all three videos are available at https://osf.io/h6qen/ (accessed on 27 September 2021).

**Ratings Items.** Subjects made four key ratings related to the interaction they had just seen. Specifically, subjects first rated the harmfulness of the journalist's behavior toward the intern (1 = entirely harmless, 4 = entirely harmful), then the reasonableness of the journalist's behavior toward the intern (1 = entirely unreasonable, 4 = entirely reasonable; reverse scored). Next, we told subjects that as a result of the interaction, the White House took away the journalist's press pass, meaning he was banned from the White House. Subjects then rated the White House's response (1 = entirely unreasonable, 4 = entirely reasonable). We then told subjects that a federal judge later ruled that taking away the journalist's press pass was a violation of his right to a fair and transparent process, ordering that the ban be lifted. Subjects then rated the judge's ruling (1 = entirely unreasonable, 4 = entirely reasonable; reverse scored).

Following these ratings, subjects provided information about their political affiliation and basic demographics, as in the previous experiments. We also administered several exploratory measures, asking subjects to rate how familiar they were with the events shown in the video, prior to the study (1 = entirely unfamiliar, 4 = entirely familiar), as well as questions variously addressing their prior familiarity with specific pieces of information related to the event and its aftermath, characteristics of the video version they observed, if they had looked up any related information during the study, and the purpose of the study; we do not report results for most of these measures here. The data are available at https://osf.io/h6qen/ (accessed on 27 September 2021).

#### *4.2. Results and Discussion*

We analyzed only the data from subjects who gave complete responses, and we did not exclude subjects on any other basis, contrary to our preregistration. Most subjects did not look up any related information (97%).

Of the 300 subjects, 80 identified as Republicans, 133 as Democrats, and 87 as Other (or none). Distributions of the political leaning variable were consistent with these data: The modal selection was "somewhat conservative" for Republicans, "somewhat liberal" for Democrats, and "Moderate" for Other.

Recall that our primary question was: To what extent does political affiliation influence how people interpret video footage of a real-world news event? To answer that question, we first calculated, for each subject, an average of their ratings across the four key items. We preregistered to conduct multivariate analyses across these four ratings, but because they were highly correlated (*r*s = 0.58–0.69; Cronbach's α = 0.87) we chose instead to combine them for univariate analysis (but conducting the preregistered analyses leads to similar results and conclusions; see Supplementary Material). Higher scores on this composite measure reflect more negative interpretations of the journalist's behavior. Table 1 shows the mean composite rating for each condition.

We then examined subjects' composite rating as a function of the video version they observed and their political affiliation. A two-way ANOVA revealed only a main effect of political affiliation, suggesting that when it came to how negatively people interpreted the journalist's behavior, only political affiliation mattered *F*(2, 291) = 28.95, *p* < 0.01, η2 p = 0.166. More specifically, Tukey-corrected post hoc comparisons revealed that Republicans rated the journalist's behavior more negatively than did Democrats ( *M*Diff = 0.92, 95% CI [0.64, 1.21], *p* < 0.01) and Others ( *M*Diff = 0.68, 95% CI [0.37, 0.99], *p* < 0.01).

We also included age as a covariate in an additional exploratory RM-ANCOVA and found that each year of aging was associated with a shift in judgment about the journalist's behavior, but the direction and strength of this shift depended on political affiliation, *<sup>F</sup>*Age x Political Affiliation(2, 292) = 4.48, *p* = 0.01, η2 p = 0.030. More specifically, for Democrats only, each year of aging was associated with a statistically significant shift toward a more positive interpretation of the journalist's behavior, *B* = −0.015, *t*(130) = 2.34, *p* = 0.02.

These findings indicate that concerns over the suggestive nature of the altered video may have been unwarranted. What, then—if not the video—drives the observed differences across the political spectrum? One possibility is prior familiarity with the event itself. To explore this possibility, we split subjects into two groups classified according to their ratings of prior familiarity with the event: Subjects who reported they were entirely or somewhat unfamiliar with the event were classified as "unfamiliar" (*n* = 146), while subjects who reported they were somewhat or entirely familiar with the event were classified as "familiar" (*n* = 154). We then re-ran the two-way ANOVA for each of these groups in turn. Although exploratory, the results sugges<sup>t</sup> that familiarity mattered: The only statistically significant factor was political affiliation—with the same pattern of means as above—and only among those who were already familiar with the event (Familiar: *p* < 0.01; Unfamiliar: *p* = 0.08).

We conducted Experiment 2b to replicate these findings with a simplified design and a slightly larger sample.

## **5. Experiment 2b**

The preregistration for this experiment is available at https://aspredicted.org/437a8 .pdf (accessed on 27 September 2021). The data were collected between 18 September and 21 November 2019.
