Every time a viewer's eye moves while watching a video, visual perception is neurologically suppressed for 200–400 milliseconds. This is saccadic suppression — the brain's mechanism for preventing blur perception during rapid eye movement. A viewer with a high saccade frequency is essentially watching your video with the lights off for a significant fraction of the total runtime.
Coefficient K quantifies this relationship: it is the ratio of fixation duration to saccade frequency. K > 1.2 indicates productive, sustained attention — the viewer's gaze is anchored and processing is occurring. K < 1.2 indicates the viewer is in exploratory scan mode, searching for either an anchor point or the swipe action.
Why Platforms Measure K
Platforms integrating gaze-tracking metrics reward videos that achieve and maintain K > 1.2 in their test cohorts. A high K coefficient is interpreted as depth of processing — the algorithm infers that the content is holding the viewer's attention productively and elevates distribution priority. Low K values signal that viewers are searching for a reason to continue, and the algorithm treats this as a weak retention signal.
Foveal Locking: The AOI Principle
The primary technique for maintaining high K is foveal locking: ensuring that the primary Area of Interest (AOI) remains within 10–15% of the frame center at all times. This minimizes the need for visual search, reduces saccade frequency, and extends primary fixation duration.
Practical implementation:
- Position the primary subject (face, product, text) within 10–15% of frame center at all times during critical content moments
- Execute dynamic cropping when the action moves outside this zone rather than following with camera movement (camera movement induces corrective saccades)
- Minimize background visual complexity — each additional moving element in the periphery induces exploratory saccades that fracture K
- Reduce rapid camera transitions; each positional shift induces corrective saccades that reduce K below the 1.2 threshold
Post-Saccadic Semantic Alignment
A second, more advanced K-optimization technique: timing scene cuts and semantic element appearances to coincide with the end of average saccade duration (~100ms). When a key piece of information appears precisely as the first post-saccadic fixation lands, the brain captures it in a single fixation without needing additional micro-saccades for correction.
This requires: scheduling cut points at multiples of approximately 100ms, introducing a relative anchor frame immediately after each movement-heavy sequence, and ensuring key text or visual elements remain visible for a minimum of 200–400ms (shorter durations force additional micro-saccades and fragment comprehension).
The Brutal Truth About Foveal Locking
Foveal locking is now common practice. The algorithm treats K > 1.2 as a baseline expectation, not a differentiating signal. A centered AOI and adequate fixation duration are necessary conditions to avoid distribution penalization — they are not sufficient to drive virality. Without layered originality on top of this technical foundation, a perfectly foveal-locked video will be algorithmically safe and cognitively boring.
The strategic implication: foveal locking is hygiene, not strategy. Establish it as a technical baseline and focus creative energy on the elements that drive differentiation — hook structure, psychological trigger density, and viral coefficient inputs.
How VIRO Uses K and Foveal Analysis
VIRO's RICE Engine V5 includes visual attention analysis as part of the retention curve integrity evaluation. It identifies frames where peripheral distractors are likely to induce saccades that fracture K, flags camera movement patterns that generate corrective saccade sequences, and identifies post-saccadic alignment failures where key semantic elements appear during suppression windows.