Video Stimuli
Version: v1 (current)
Play video content to participants for attention, emotion, or instructional research.
Overview
The Video stimuli task presents dynamic video content using the HTML5 video player. It supports auto-play, playback controls, and can require participants to watch the full video before advancing.
Common research uses include:
- Social cognition: View social interactions or scenarios
- Emotion recognition: Watch dynamic facial expressions
- Instructional videos: Demonstrate procedures before tasks
- Stimuli with temporal dynamics: Present time-varying content
Where to Configure
Study form → Tasks → Stimuli tasks → Video → Configure.
Configuration Parameters
Video-Specific Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Media URL | string | '' | URL of the video file (MP4 recommended) |
| Auto Play | boolean | true | Start playing automatically when displayed |
| Show Controls | boolean | false | Show video player controls (play, pause, seek) |
| Loop | boolean | false | Repeat the video continuously |
| Mute | boolean | false | Start with audio muted |
| Require Full Playback | boolean | true | Participant must watch to the end before advancing |
| Advance On End | boolean | true | Automatically advance when the video finishes |
Common Stimuli Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Button Text | string | 'Continue' | Text for advancement button |
| Background Color (hex) | string | 'FFFFFF' | Background color |
Participant Flow
- The video begins playing (automatically if Auto Play is on, or the participant clicks play).
- If controls are shown, the participant can pause, seek, or adjust volume.
- If Require Full Playback is enabled, the Continue button is disabled until the video ends.
- After the video finishes, the task advances automatically or the participant clicks Continue.
Design Recommendations
- Format: Use MP4 with H.264 encoding for maximum browser compatibility.
- Resolution: 720p minimum; test buffering with your target audience's connection speed.
- Length: Keep clips short and consistent across conditions; long videos risk participant disengagement.
- Captions: Consider adding captions for accessibility.
- Controls: Hide controls when you need participants to watch passively; show controls when self-paced viewing is acceptable.
- Full playback: Enable Require Full Playback for critical stimuli to ensure complete exposure.
Common Issues and Solutions
| Issue | Solution |
|---|---|
| Video doesn't play | Check the URL; ensure the video format is MP4/H.264; test on the target browser |
| Video buffering delays | Preload the video; reduce quality; use a CDN; allow time for loading |
| Audio not playing | Check browser autoplay policies; some browsers block autoplay with sound. Consider starting muted |
| Participants skip the video | Enable Require Full Playback; disable the Continue button until playback completes |
Data Output
Markers and Responses
Markers (stimulus_shown):
{
"type": "stimulus_shown",
"ts": "2024-01-01T00:00:01.000Z",
"hr": 1234.56,
"data": {
"type": "video",
"url": "https://example.com/videos/clip.mp4"
}
}
Markers (response_recorded):
{
"type": "response_recorded",
"ts": "2024-01-01T00:00:30.000Z",
"hr": 30234.56
}
Response Data:
{
"type": "video"
}
Summary Artifact
None. The video stimulus task does not generate a summary artifact.
References
- Bradley, M. M., & Lang, P. J. (2007). The International Affective Picture System (IAPS) in the study of emotion and attention. In J. A. Coan & J. J. B. Allen (Eds.), Handbook of Emotion Elicitation and Assessment (pp. 29-46). Oxford University Press.