Image Sequence Stimuli

Version: v1 (current)

Display multiple images one after another in a fixed or randomized order, with optional auto-advance timing.

Overview

The Image Sequence stimuli task shows multiple images one at a time in succession. It supports both self-paced advancement (click Next) and automatic timed advancement. This task is useful for rapid serial visual presentation (RSVP), sequential memory encoding, and any paradigm requiring ordered image presentation.

Common research uses include:

• RSVP paradigm: Rapid image streams for attentional research
• Attentional blink: Image-based attentional blink studies
• Sequential memory: Remember image order or specific items
• Dynamic scene perception: Show scene changes over time

Where to Configure

In the study editor, add a new task and choose Stimuli → Image sequence. Or add a base "Stimuli" task and set Type to "Images (sequence)".

Setup Steps

1. Click Upload images and select one or more images.
2. After at least one image is uploaded, a hint appears above the list reminding you that you can drag to reorder.
3. Arrange order by dragging items in the list. The first item shows first.
4. To remove an image, click the x on its row.
5. Optional: enable Randomize sequence order to shuffle the list for each participation session.
6. Optional: enable Auto-advance and set "Advance after (ms)". Even with auto-advance, the participant can still click Next to proceed.
7. Optional: when auto-advance is off, set "Minimum time before next (ms, manual advance)" to require each image to stay on screen for a minimum time before the participant can use Next or Back (0 turns this off).
8. Click Save.

Configuration Parameters

Sequence-Specific Parameters

Parameter	Param key	Type	Default	Description
Images	stimuli_media_urls	file upload	-	Upload one or more images to display in sequence
Randomize Sequence Order	images_sequence_randomize	boolean	false	Shuffle the image order for each participant session
Auto-advance	images_sequence_auto_advance	boolean	false	Automatically advance to the next image after a set duration
Advance After (ms)	images_sequence_auto_advance_ms	number	2000	Milliseconds to display each image before auto-advancing (minimum 100). Only stored when auto-advance is enabled.
Minimum Time Before Next (ms, manual advance)	images_sequence_min_time_before_next_ms	number	0	When auto-advance is off, the minimum time (in milliseconds) each image must be shown before the participant can use Next or Back. Default 0 turns this off. Only stored when greater than 0.
Allow Back	images_sequence_allow_back	boolean	false	Shows a Back button that lets the participant return to the previous image. Hidden on the first image. Revisiting an image adds to its total viewing time rather than creating a separate entry.
Show Mic Meter	images_sequence_show_mic_meter	boolean	false	Shows a cue-only microphone level meter (icon + level bars) while an image is displayed, as a visible sign that the microphone is active. Visual cue only — never records or transcribes; the session recording already captures audio.
Show Countdown	images_sequence_show_countdown	boolean	false	Shows a "Time remaining" countdown for the current image's auto-advance. Only shown when Auto-advance is enabled.
Show Index	images_sequence_show_index	boolean	false	Shows the current position as "N / total" while an image is displayed.

Beyond the parameters listed above, there are no other configurable options. The Next/Back button labels come from the shared task UI, and there is no per-task background-color option. Beyond the parameters above, the only stored config is the main and hint instruction text (rich-text editors).

Participant Flow

1. The participant sees one image at a time, centered on the page. If Show Index is enabled, the current position ("N / total") is shown above the image. If Show Mic Meter is enabled, a live microphone level indicator appears.
2. Clicking Next moves to the next image. On the last image, Next finishes the task.
3. If Allow Back is enabled, a Back button (hidden on the first image) lets the participant return to the previous image.
4. If Auto-advance is enabled, images also advance automatically after the configured interval (in milliseconds). If Show Countdown is also enabled, the remaining time is shown counting down.
5. If Auto-advance is off and Minimum time before next (ms, manual advance) is set, each image must stay on screen for that minimum time before the participant can use Next or Back.
6. If Randomize sequence order is enabled, the image order is shuffled when the session starts and stays fixed for that participant.

Design Recommendations

• Image quality: Use high-contrast images sized for screens; the app scales images to fit without cropping.
• Order: Keep the order simple and communicate expectations in the task instructions if needed.
• Encoding studies: Use fixed auto-advance durations (e.g., 2000 ms (2 s) per image) for consistency.
• RSVP: For rapid presentation, use very short advance times (200-500 ms per image).
• Practice stimuli: Use different images for practice than for the main task.
• Counterbalancing: Enable randomization to counterbalance order effects across participants.

Common Issues and Solutions

Issue	Solution
Images don't load	Use absolute URLs; check CORS settings; test on the target browser
Participants skip too quickly	Use Auto-advance with a fixed duration; disable manual advancement if needed
Inconsistent display durations	Use Auto-advance for precise timing control
Image order matters but is randomized	Disable Randomize sequence order; arrange images manually in the editor

Data Output

Markers and Responses

The task records high-resolution timestamps in the markers collection and writes one accumulated response row per image at task completion (not a single end-of-task envelope), so the Scoring tab and export show one trial per image, matching the Timeline's per-image segments.

Markers (sequence_order):

{
  "type": "sequence_order",
  "ts": "2024-01-01T00:00:01.000Z",
  "hr": 1234.56,
  "data": {
    "order": ["image_a.jpg", "image_c.jpg", "image_b.jpg"],
    "randomized": true
  }
}

order uses each image's display name (the original filename you uploaded, or a readable name for bundled images), never a raw storage path.

Markers (stimulus_shown):

{
  "type": "stimulus_shown",
  "ts": "2024-01-01T00:00:01.100Z",
  "hr": 1334.56,
  "data": {
    "index": 0,
    "filename": "image_a.jpg",
    "url": "https://example.com/images/image_a.jpg"
  }
}

Emitted every time an image is shown, including when the participant uses Back to revisit an earlier image.

Markers (manual_next) -- when participant clicks Next:

{
  "type": "manual_next",
  "ts": "2024-01-01T00:00:03.500Z",
  "hr": 3734.56,
  "data": {
    "index": 0
  }
}

Markers (manual_prev) -- when participant clicks Back (only possible when Allow Back is enabled):

{
  "type": "manual_prev",
  "ts": "2024-01-01T00:00:04.200Z",
  "hr": 4434.56,
  "data": {
    "index": 1
  }
}

Markers (autoadvance_next) -- when auto-advance timer fires:

{
  "type": "autoadvance_next",
  "ts": "2024-01-01T00:00:03.000Z",
  "hr": 3234.56,
  "data": {
    "index": 0,
    "scheduled_offset_ms": 2000,
    "drift_ms": 3
  }
}

Markers (stimulus_hidden) -- emitted right before advancing away from an image (Next, Back, auto-advance, or moderator advance), bounding that image's display segment:

{
  "type": "stimulus_hidden",
  "ts": "2024-01-01T00:00:03.400Z",
  "hr": 3634.56,
  "data": {
    "index": 0
  }
}

Markers (stimulus_aoi) -- recorded after each image paints, capturing its viewport bounds for gaze joining:

{
  "type": "stimulus_aoi",
  "ts": "2024-01-01T00:00:01.150Z",
  "hr": 1384.56,
  "data": {
    "index": 0,
    "stimulus_bounds": { "x_pct": 25, "y_pct": 20, "width_pct": 50, "height_pct": 60 }
  }
}

No response_recorded marker is emitted for this task: the per-image stimulus_shown / stimulus_hidden markers already bound each image's Timeline segment.

Response Objects

One accumulated response row per distinct image, emitted at task completion:

{
  "type": "images_sequence",
  "trial_index": 1,
  "image_index": 0,
  "image_name": "image_a.jpg",
  "viewing_time_ms": 2000,
  "visit_count": 1,
  "source": "viewed"
}

• type: always "images_sequence".
• trial_index: 1-based trial number (equals image_index + 1).
• image_index: zero-based position of this image in the presented (possibly randomized) order.
• image_name: the image's display name (your original filename, or a readable name for bundled images) — never a raw storage path.
• viewing_time_ms: total time this image was displayed, added up across all visits. If Allow Back is enabled and the participant revisits an image, the time from each visit adds to this same total.
• visit_count: number of times this image was displayed — 1 with no back-navigation, higher if the participant returned to it.
• source: always "viewed".

Images are passively viewed, not responded to, so these rows have no responded field at all — this is intentional (not a missing value), since there is no participant response to a viewed image to judge as answered or not.

Per-Visit Export File

When Allow Back is enabled and used, the accumulated response row above tells you the total time spent on each image and how many times it was shown, but not the order of the back-and-forth. For that detail, the export bundle ("Download All" on the participation page) includes one image_sequence_visits_<n>.json file per Image Sequence task, listing every individual showing in order: which image, whether it continued forward or returned to an earlier image, and how long that one showing lasted. The Scoring tab shows the same detail in an expandable "Image sequence visits" section whenever a revisit occurred. See the Participation Dashboard guide for the full export-file catalog.

Summary Artifact

None. The image sequence 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.

See Also

• Image - Single image presentation
• Image Grid - Display multiple images simultaneously
• Text - Text content presentation