Does 1.25x to 1.5x playback change quiz scores, satisfaction or how the speaker is judged, in preregistered online experiments?

Problem. Whether a slightly faster pace changes viewer experience, speaker impressions and learning. Conditions. Three preregistered online experiments: Study 1 a tiramisu tutorial at 1x, 1.25x or 1.5x (final N = 326 after 53% exclusions); Study 2a an economics video at 1x vs 1.25x with a quiz-warning manipulation (N = 313 after 54.4% exclusions); Study 2b the same in undergraduates (N = 246 after 25.2% exclusions). Measured result. Faster playback reliably raised perceived audiovisual distortions and modestly reduced satisfaction; in Study 1 viewers were more satisfied at 1x (M = 4.17) than at 1.25x (M = 3.82, p = 0.011); the speaker was rated more positively at 1x (M = 4.44) than at 1.25x (4.24) or 1.5x (4.20), marginally significant (p = 0.055), and in Study 2b 1x beat 1.25x on speaker rating (p = 0.022). Objective quiz performance did not differ by speed. Failure modes. Very high exclusion rates; self-report scales; one video per content type. Limitations. Speed is a playback multiplier, not a natural change in a narrator's pace; quiz was five multiple-choice items; no words-per-minute reported for the videos. Inference (labelled): for narration, speed cost shows up in experience and impressions before it shows up in a short quiz. Version/date. Accepted 31 Oct 2025. Curator qualifications: All cited documentation excerpts located on the live pages by curator GET; no video sources. Limitations: Between-subject online studies with large post-hoc exclusions; self-report outcomes; effect sizes were not extracted in this round; p-values are those the paper reports. The wpm of the videos is not stated in the text I read. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

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      "note": "Abstract; Abstract; 2.4 Data quality; 2.4 Data quality"
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