A saccade is a rapid, simultaneous movement of both eyes between two or more focal points in the same direction. Also described as "jerks," these discontinuous jumps allow the brain to scan an environment rather than viewing a scene in a steady, fixed motion. Understanding these movements is critical for marketers and SEO practitioners because they determine how users consume text and which visual elements on a page successfully capture attention.
What is a Saccade?
A saccade is the eye's mechanism for relocating gaze direction to align the fovea with a target. In contrast to smooth-pursuit movements, where the eyes track a moving object steadily, saccades are abrupt and jumpy. Human eyes make several stops when scanning a digital interface or reading, moving as fast as physically possible between each point of fixation.
This behavior occurs because the [human fovea is very small, covering only 1 to 2 degrees of vision] (Wikipedia). Because only this tiny area provides high-resolution detail, the eyes must constantly move to build a coherent mental map of a full scene.
Why Saccade matters
- Scene resolution. Saccades allow the eyes to capture small parts of a scene in high detail so the brain can assemble them into a continuous mental representation.
- Reading efficiency. During silent reading, the eyes move in a succession of discontinuous movements to grasp objects of attention quickly.
- Attention measurement. Eye-tracking tools use velocity-based algorithms to detect saccades, helping researchers determine what users are actually processing.
- Cognitive insights. Changes in saccadic behavior, such as increased delays or errors, can provide data on user focus and psychiatric conditions like ADHD.
- User experience. Humans make [two to three fixations every second] (Wikipedia), meaning layouts must be optimized for rapid, fragmented scanning.
How Saccade works
Saccades are "ballistic" movements, meaning the brain determines the trajectory before the motion begins. Once the eye starts a saccade, its path and speed cannot be altered.
- Selection. The brain identifies a target in the peripheral vision or follows an internal command to explore.
- Initiation. The brain takes time to program the movement. [Saccades to unexpected stimuli typically take about 200 milliseconds to initiate] (Wikipedia).
- Execution. The eye muscles fire at their full rate. For large movements, [peak angular speed reaches up to 700°/s in humans] (Wikipedia).
- Suppression. To prevent the world from appearing blurry, the brain engages in "saccadic masking." This suppresses visual processing during the jump so the user does not perceive the image smear.
- Fixation. The eye stops at the new focal point to gather high-resolution data before the next jump.
Types of Saccade
Saccades are categorized by their intended goal or the nature of the stimulus:
- Reflexive: Triggered by the sudden appearance of a visual cue in the periphery.
- Scanning: Self-directed movements used to explore an environment or look for specific information.
- Antisaccade: A voluntary movement where the eyes look away from a visual stimulus.
- Memory-guided: Moving the eyes toward a location where a stimulus used to be, based on memory.
- Predictive: Keeping gaze on an object moving in a predictable pattern.
- Express Saccades: Reflex-like movements that bypass complex brain circuits, having a [latency of less than 85 ms] (ScienceDirect).
Best practices
Design for scanability. Since the eyes jump between focal points, use clear headings and bullet points. This helps the user’s horizontal and vertical scanning saccades land on the most important information quickly.
Optimize line lengths. For text-heavy pages, keep line lengths moderate. Broad line breaks can disrupt the rhythm of reading saccades and lead to word skipping.
Leverage focal points. Use high-contrast elements or images to trigger reflexive saccades. This "grabs" the user's attention and directs the fovea to specific calls to action.
Account for visual masking. Do not place critical moving information in a way that coincides with where a user is likely to jump their gaze. The brain may hide that information during the movement.
Common mistakes
Mistake: Using redundant words in headers. Fix: The mind often skips over words it deems unimportant, such as multiple "the" or "and" instances, especially during line breaks. This "Paris in the the Spring" effect proves that users do not read every word.
Mistake: Assuming users "see" everything while their eyes are moving. Fix: Understand that the brain suppresses blur during the jump. If an object moves or changes during a saccade, the user likely will not notice the transition.
Mistake: Overwhelming the periphery. Fix: If too many elements compete for reflexive saccades, the user may experience fatigue or fail to fixate on the intended conversion point.
Examples
Example scenario (Reading): When a user reads a blog post, their eyes do not move smoothly across the line. Instead, they make small jumps (saccades) and pauses (fixations). Short words like "of" or "a" are often bypassed entirely by the eye, with the brain filling in the gaps.
Example scenario (Ad Placement): A sidebar ad pops up unexpectedly. This triggers a reflexive saccade, pulling the user's gaze away from the main content. If the user then makes an intentional antisaccade back to the text, the ad has succeeded in capturing initial attention but may have disrupted the user's goal.
Saccade vs Smooth Pursuit
| Feature | Saccade | Smooth Pursuit |
|---|---|---|
| Movement Style | Abrupt, jerky jumps | Steady, smooth tracking |
| Control | Ballistic (pre-programmed) | Feedback-driven |
| Goal | Shift gaze to new target | Maintain gaze on moving target |
| Speed | Extremely fast (up to 700°/s) | Restricted to object speed |
| Visual Input | Suppressed during movement | Continuous processing |
FAQ
What is the "saccadic main sequence"? The main sequence is a specific relationship between a saccade's size and its speed. For jumps up to 20 degrees, the [velocity increases linearly with the amplitude] (EyeWiki). For example, a 10 degree jump is associated with a speed of 300°/s, while a 35 degree jump reaches over 475°/s.
How long does a saccade last? The duration of the movement itself is very short. Depending on the size of the jump, a [saccade typically lasts between 20 and 200 ms] (Wikipedia). This makes them some of the fastest movements the human body can produce.
Can I see my own saccades? Normally, no, because of saccadic masking. However, you can use a digital mirror with a slight delay. If you look from eye to eye in a cellphone’s front-facing camera, the signal-processing delay allows you to see the end of your own eye movement.
What are microsaccades? Microsaccades are tiny, involuntary versions of voluntary saccades that occur while you are trying to keep your eyes fixed on a single point. These [amplitudes vary from 2 to 120 arcminutes] (Wikipedia). They help prevent the visual scene from fading by constantly shifting the image on the retina.
Are saccades different in people with Parkinson's or ADHD? Yes. Certain conditions change how saccades are performed. For instance, individuals with [ADHD show an increase in antisaccade errors] (Wikipedia), meaning they have more difficulty suppressing the urge to look at a sudden visual stimulus.
