Metric Timeline

A Metric Timeline shows how an eye-tracking metric changes over the course of a stimulus. The metric is computed in a moving time window, for example the average fixation duration in each 1000 ms window, stepped forward every 100 ms. Each participant’s values are drawn either as one row of a color-coded heatmap or as one line in a line chart, so trends, patterns, and fluctuations in visual attention and processing load become visible over time.

Scope	One stimulus, any participant selection
Input	Fixations on the stimulus, within the time range and AOI selection
Metric Library	One windowed scalar metric, computed per participant (see Metrics)

When to Use It

• Track cognitive processing load: An increase in average fixation duration over a timeline segment can indicate areas of high visual complexity or cognitive load.
• Observe search trends: Track when participants are scanning rapidly (low fixation duration, high count) vs. processing deeply (high fixation duration).
• Compare participants with the group: In the Overlay view, each participant’s line runs against the mean line and the band between the 25th and 75th percentiles.

Reading the Plot

• Horizontal axis: elapsed time in milliseconds. The axis title names the window and the step, for example 1000 ms window, 100 ms step. Each value is placed at the middle of its window.
• Heatmap view: one row per participant. Cell color is the metric value in that window; the color bar below the plot is titled with the metric’s label and unit. Gray cells are windows with no value, such as a window without fixations or one past the end of a recording.
• Overlay view: the vertical axis is the metric value. Every participant is a faint line, the red line is the mean across participants, and the red shaded band spans the 25th to 75th percentile.

Add a Metric Timeline

1. Load your data: drop the files anywhere on the page, or use Import. See Uploading Data for the supported formats.
2. In the rail on the left, click Add Visualization, then Per participant > Metric Timeline. When another plot is selected, the new one opens on its stimulus and participants.
3. The pane on the right opens with the plot’s settings. Pick the Stimulus first, then the Metric.

To move, resize, duplicate, or remove the card, see Plot Manipulation.

Settings

Select the card to open its settings in the Pane (a bottom sheet on mobile). The sections, in pane order:

Stimulus

Choose the stimulus to analyze. Gaze data will be filtered and binned along this stimulus’s recorded timeline.

• Edit stimuli & selections: Opens the Stimuli Library to manage stimulus files and build stimulus selections.

Participants

Filter the analysis by participant selection.

• Participant selection: All or a saved participant selection. Hide participants without data leaves out those with no recording on the stimulus.
• Edit participants & selections: Opens the Participant Library to rename, merge, and build participant selections.

Metric

Configure the windowed scalar metric to track. The metric must compute a single value per window (output shape scalar, windowing required); for how raw metric shapes become windowed scalar projections, see the Metrics Library Overview and its category pages.

• Select metric: A dropdown of all metric instances in the library that satisfy the windowed scalar contract:
  • Average fixation duration (avgFixationDuration-any-windowed): Computes the mean duration of fixations landing within each moving window (see Durations). This is the default.
  • Fixation count (fixationCount-any-windowed): Tracks the frequency of fixations per window (see Counts & Latency).
• Edit metric library: Opens the Metric Library modal where you can customize window parameters (window size and step size, e.g. 1000ms window with 100ms step) or define custom windowed scalar metrics.

Visualization

Configure the visual presentation. The view decides which further controls appear; they are listed under the view that reveals them.

• Select view:
  • Heatmap: Renders a grid where rows represent participants and columns represent time windows. Cell color represents the metric value. This is the default.
    • Color scale picker: Minimum, middle, and maximum colors of the heatmap intensity gradient.
  • Overlay: Renders a line graph where the horizontal axis is time and the vertical axis is the metric value, with one line per participant, the mean line, and the 25th to 75th percentile band.

Time range

Filter the temporal range.

• Start / ms: Limit the minimum time boundary.
• End / ms (0 = Auto): Limit the maximum time boundary, or leave at 0 for automatic duration matching.

Areas of Interest

Filters which Areas of Interest (AOIs) are active for the metric calculation. No fixations are dropped, and whole-stimulus metrics (the -any instances) are unaffected.

• AOI selection: A dropdown containing All and saved AOI selections; AOIs outside the picked selection count as no-AOI in this plot.
• Edit AOIs & selections: Opens the AOI Library to customize names, colors, merges, and selections.

Export

Located at the bottom of the Pane:

• Download plot: Opens the Figure Export dialog to save the timeline plot as a PNG or JPG.
• Download data: Opens the Metric Data export preset to this plot’s metrics, stimulus, participant selection, time range and AOI selection.

Interactivity

• Window under the pointer: Hovering marks the window and step at the pointer; in the Overlay view, the hovered participant’s line is emphasised. The tooltip shows the Participant, the Window (start to end in ms), and the value under the metric’s axis label, or No data.
• Linked hovering: The hovered moment and participant are marked in the other plots of the workspace, and moments and participants hovered elsewhere are marked here, see Linked Hovering Across Plots.

Related

• AOI Timeline: how attention is split between AOIs over time, instead of one metric.
• Scarf Plot: the raw AOI sequence behind the windowed values.
• Metric Matrix: one whole-recording value per participant and stimulus, without windows.