physics

Peripheral drift illusion

Peripheral drift illusion is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Peripheral drift illusion rather than just read about it. In short: The peripheral drift illusion (PDI) refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery. This illusion was first described by Faubert and Herbert (1999), although a similar effect called the "escalator illusion" was reported by Fraser and Wilcox (1979).

Key takeaways

Peripheral drift illusion belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Peripheral drift illusion to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Peripheral drift illusion from memory before moving on to harder problems.

Reference excerpt

The peripheral drift illusion (PDI) refers to a motion illusion generated by the presentation of a sawtooth luminance grating in the visual periphery. This illusion was first described by Faubert and Herbert (1999), although a similar effect called the "escalator illusion" was reported by Fraser and Wilcox (1979). A variant of the PDI was created by Kitaoka Akiyoshi and Ashida (2003) who took the continuous sawtooth luminance change, and reversed the intermediate greys. Kitaoka has created numerous variants of the PDI, and one called "rotating snakes" has become very popular. The latter demonstration has kindled great interest in the PDI. The illusion is easily seen when fixating off to the side of it, and then blinking as fast as possible. Most observers can see the illusion easily when reading text with the illusion figure in the periphery. The motion of such illusions is consistently perceived in a dark-to-light direction. Two papers have been published examining the neural mechanisms involved in seeing the PDI (Backus & Oruç, 2005; Conway et al., 2005). Faubert and Herbert (1999) suggested the illusion was based on temporal differences in luminance processing producing a signal that tricks the motion system. Both of the articles from 2005 are broadly consistent with those ideas, although contrast appears to be an important factor (Backus & Oruç, 2005).

Rotating snakes

Rotating snakes is an optical illusion developed by Professor Akiyoshi Kitaoka in 2003. A type of peripheral drift illusion, the "snakes" consist of several bands of color which resemble coiled serpents. Although the image is static, the snakes appear to be moving in circles. The speed of perceived motion depends on the frequency of microsaccadic eye movements (Alexander & Martinez-Conde, 2019).

Gallery

References

Inline citations

General references Alexander, R. G., Martinez-Conde, S. (2019). Fixational eye movements. Eye Movement Research. Springer, Cham, 104–106, doi:10.1007/978-3-030-20085-5_3. Backus, B. T., Oruç, İ. (2005). Illusory motion from change over time in the response to contrast and luminance. Journal of Vision, 5(11), 1055–1069, [1], doi:10.1167/5.11.10. Conway, B. R., Kitaoka, A., Yazdanbakhsh, A., Pack, C. C., Livingstone, M. S. (2005). Neural basis for a powerful static motion illusion. Journal of Neuroscience, 25, 5651–5656. Faubert, J., Herbert, A. M. (1999). The peripheral drift illusion: A motion illusion in the visual periphery. Perception, 28, 617–622. Fraser, A., Wilcox, K. J. (1979). Perception of illusory movement. Nature, 281, 565–566. Kitaoka. A., Ashida. H. (2003). Phenomenal characteristics of the peripheral drift illusion. Journal of Vision, 15, 261–262.

External links Rotating snakes at Akiyoshi's illusion pages Rotating rings at Sarcone's optical illusion pattern page These patterns move, but it’s an illusion Deprecated link archived 2013-09-01 at archive.today by Smithsonian Research Lab Does your pet see Peripheral drift? a slideshow designed for testing on animals

Illustrations

Peripheral drift illusion: Two images that exhibit peripheral drift illusion. The different pattern of light and dark causes the two circles to appear to rotate in opposite directions. — Two images that exhibit peripheral drift illusion. The different pattern of light and dark causes the two circles to appear to rotate in opposite directions.

Worked examples

Example 1 — a first encounter with Peripheral drift illusion

Start with the simplest possible case. Write down what Peripheral drift illusion claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Peripheral drift illusion before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Peripheral drift illusion ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Peripheral drift illusion

In research: Peripheral drift illusion appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Peripheral drift illusion in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Peripheral drift illusion is common in secondary-school and first-year university syllabi. It links to neighbouring topics Optical illusions, Vision, so understanding it makes those chapters shorter.
In everyday life: Look for Peripheral drift illusion outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Peripheral drift illusion in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Peripheral drift illusion means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Peripheral drift illusion out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Peripheral drift illusion in simple terms?

Why does Peripheral drift illusion matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Peripheral drift illusion?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Peripheral drift illusion.