Surreal illustration of eye representing Motion Perception

Motion Perception: How Your Brain Interprets Movement

Mira Elwood monogram
Mira Elwood in Mind & Education November 2026 • 4 min read.

"Decoding the link between shape, curvature, and motion to better understand visual processing"


Our brains are incredibly skilled at interpreting the world around us, especially when it comes to motion. Imagine watching a bird fly or a car speed by—how does your brain translate these visual cues into a seamless perception of movement? Scientists have long been fascinated by this question, diving deep into the mechanisms that allow us to understand motion in its many forms.

A recent study sheds light on this intricate process, focusing on how our brains code curvature to perceive motion. Curvature, in this context, refers to the bends and shapes of objects we see. The study reveals that this curvature coding is finely tuned for motion direction, luminance (brightness), and temporal frequency (how quickly something changes).

The researchers used shape after-effects, specifically the shape-frequency after-effect (SFAE) and the shape-amplitude after-effect (SAAE), to investigate how our brains process these visual elements. Think of after-effects as visual illusions that occur after prolonged exposure to a stimulus. The SFAE and SAAE are believed to be linked to curvature-sensitive mechanisms in our visual system.

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Motion Relies on Distributed Visual Processing

Motion perception draws on visual sensory processing in the retina, lateral geniculate nucleus (LGN), and primary and secondary visual cortex. Research on curvature coding suggests that its mechanisms are selective to motion direction, with this selectivity most apparent when a stimulus provides sufficient spatiotemporal coverage. A separate modeling study explores whether second-order motion statistics derived from spatiotemporal Gabor filter responses capture motion complexity beyond first-order motion energy, particularly in mid- and high-level lateral visual regions.

Methods for Studying Form and Motion

Research on form and motion has used non-invasive brain stimulation with different visual stimuli to investigate cortico-cortical interactions in the visual cortex. The same review discusses the timing of visual processing in the ventral and dorsal streams. One limitation in interpreting motion performance is that pursuit and perceptual discrimination thresholds were higher for target acceleration than for target speed, suggesting that a shared motion-processing stage may constrain both systems. Separately, a 2025 paper reports that the INRF model explains data that challenge the so-called standard model of vision.

A Continuing Field of Study

A chapter on human visual cortex describes visual motion perception and its neural bases as a central topic in visual neuroscience. It aims to overview the brain mechanisms underlying human motion perception and is organized into four sections. The evolutionary origins of specialized forms such as second-order motion, structure-from-motion, and biological motion remain open questions; the source notes that whether these forms rely on dedicated mechanisms is not settled.

What are SFAE and SAAE, and How do They Relate to Motion?

Surreal illustration of eye representing Motion Perception

The shape-frequency after-effect (SFAE) and shape-amplitude after-effect (SAAE) are visual illusions that help scientists understand how our brains perceive shape and curvature. In essence, these after-effects cause a shift in how we see the frequency and amplitude of shapes after we’ve been exposed to an adapting stimulus.

Imagine you stare at a sine-wave-shaped contour for a while. Afterward, when you look at a similar but slightly different contour, your perception of its shape-frequency and shape-amplitude will be altered. This distortion, this shift in perception, is what researchers call SFAE and SAAE.

  • Shape-Frequency After-Effect (SFAE): Adaptation to a sine-wave-shaped contour causes a shift in the apparent shape-frequency of a test contour in a direction away from that of the adapting stimulus.
  • Shape-Amplitude After-Effect (SAAE): Adaptation to a sine-wave-shaped contour causes a shift in the apparent shape-amplitude of a test contour in a direction away from that of the adapting stimulus.
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Limits in the Evidence and Models

A study of feature-continuous motion reports clear evidence of ROOD responses in its data and subjective reports, but says there were not enough trials to assess whether those responses vary with direction. Research on temporal limits likewise notes that its human psychophysical and neurophysiological experiments cannot determine the extent of neuronal integration or its contribution to measured temporal resolution. A curvature paper cautions that models of curvature detection and discrimination do not necessarily explain how curvature is represented in the visual system. Another study notes that adaptation to curvature found with static stimuli may be difficult to distinguish from orientation adaptation.

Attention, Luminance, and Computational Models

A meta-analysis covering 37 independent samples and 76 effects found that attention significantly and substantially enhanced motion adaptation (Cohen’s d = 1.12, p < .0001). In noise, reducing mean luminance improved motion sensitivity by up to about a factor of 1.7 at temporal frequencies up to 7.5 Hz, but impaired sensitivity at 15 and 30 Hz. A computer-vision study examined how much known human psychophysical phenomena of visual motion perception can be explained by representative optical-flow estimation models.

To study the motion direction selectivity, the researchers had sinusoidal-shaped contours drift within a fixed stimulus window. In one condition, the entire contour moved (global motion), while in another, the contour was made of moving Gabor patches (local motion). The key was to see if the after-effects changed depending on whether the adaptor and test contours moved in the same or opposite directions.

Why is this Research Important?

Understanding how our brains code curvature and motion is essential for several reasons. Firstly, it deepens our fundamental knowledge of how the visual system works. Secondly, it has implications for various applications, such as improving artificial vision systems, enhancing visual rehabilitation strategies, and designing more effective visual displays. Ultimately, by unlocking the secrets of motion perception, we can gain valuable insights into the brain's remarkable ability to make sense of the dynamic world around us.

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Neuromorphic Motion Processing and New Applications

A February 10, 2026 report describes ultrafast visual processing enabled by neuromorphic motion-extraction hardware. It presents this processing as a potential information source for future human-robot interaction, with the aim of supporting smooth and responsive interaction. This is a prospective application described by the source, rather than evidence that such outcomes are already established.

Motion Perception in Everyday Experience

Motion perception is an important part of daily visual experience and involves regions supporting object motion, self-motion, eye and hand guidance, and the form of moving two- and three-dimensional objects. Patients with cerebral akinetopsia report an altered experience of motion. A 2024 study on visual perceptual learning of form–motion integration reports that transfer in non-directional motion perception depends on stimulus characteristics and highlights the potential for learning to improve internal processing efficiency. A 2023 vertical dance study used shifting dots to evoke recognizable human movement from sparse visual information.

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What is motion perception?

Motion perception is the brain's ability to interpret movement from visual cues. It involves translating what we see, like a bird flying or a car moving, into a seamless understanding of motion. This process relies on intricate mechanisms within the brain that decode various elements, including shape and changes in objects, to create a coherent perception of movement.

2

What is curvature coding, and what factors is it tuned for?

Curvature coding, in the context of motion perception, is how the brain uses the shapes and bends of objects to understand movement. It has been found that curvature coding is finely tuned for several factors: the direction of motion, luminance (or brightness), and temporal frequency, which refers to how quickly something changes in appearance. This implies that our brain analyzes the shape of moving objects to interpret their motion, taking into account brightness and speed.

3

What are shape after-effects (SFAE and SAAE), and how do they relate to the study of motion perception?

Shape after-effects, like the shape-frequency after-effect (SFAE) and shape-amplitude after-effect (SAAE), are visual illusions that occur after prolonged exposure to a stimulus. SFAE causes a shift in how we perceive the shape-frequency of an object, while SAAE causes a shift in how we perceive the shape-amplitude. Both of these effects are linked to curvature-sensitive mechanisms in our visual system. The SFAE and SAAE help in studying motion perception by revealing how adapting to specific shapes affects our subsequent perception of other shapes, providing insight into how the brain processes shape and curvature in relation to movement.

4

Why is understanding curvature and motion coding important?

The research is important because understanding curvature and motion coding enhances the understanding of the visual system. This knowledge has implications such as improving artificial vision systems by mimicking the brain's efficient processing of motion. The research could also have implications for visual rehabilitation strategies, where understanding how the brain perceives motion could aid in developing treatments for visual impairments. Furthermore, it can inform the design of visual displays to provide more effective and natural experiences.

5

What is the difference between global motion and local motion?

Global motion refers to the overall movement of an entire object or shape, while local motion refers to the movement of individual components or parts within that object. The research used sinusoidal-shaped contours drifting within a fixed stimulus window to study motion direction selectivity to see if the after-effects changed depending on whether the adaptor and test contours moved in the same or opposite directions. The distinction is important because it helps to understand how the brain integrates local cues to perceive the global motion of an object, allowing the study of how these different types of motion processing interact within the visual system.

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