<p>Mark Changizi proposed another level of understanding this illusion based on the "Perceiving the Present" hypothesis. Here is the <a href="http://news.discovery.com/human/evolution/optical-illusions-you-brain-way-ahead-130823.htm" rel="nofollow">explanation</a>:</p>

<blockquote>
  <p>Optical illusions are actually a result of our brains trying to
  predict the future.   When light hits our retina, it takes about
  one-tenth of a second for our brain to translate that signal into
  perception. This neural delay makes our brains generate images of what
  it thinks the world will look like in one-tenth of a second. It's not
  always right.</p>
  
  <p>“Your brain is slow, so you need to basically create perceptions that
  correct for that delay,” said Changizi, director of human cognition at
  2AI Labs.</p>
  
  <p>Creating an image of the very near future probably kept early humans
  alive because it kept them from bumping into dangerous objects or
  being attacked by a fast-moving predator.</p>
</blockquote>

<p>To learn more about the "<a href="http://onlinelibrary.wiley.com/doi/10.1080/03640210802035191/full" rel="nofollow">Perceiving the Present" hypothesis</a></p>

CC BY-SA 3.0
2015-03-08T14:08:15.757Z
2015-03-08T14:19:11.920Z
2015-03-08T14:19:11.920Z
MagTun
<p>This is a type of <a href="http://en.wikipedia.org/wiki/Illusory_motion" rel="nofollow noreferrer">illusory motion</a> (or motion illusion) called a <a href="https://en.wikipedia.org/wiki/Peripheral_drift_illusion#Gallery" rel="nofollow noreferrer">peripheral drift illusion</a>:</p>
<div class="s-table-container">
<table class="s-table">
<thead>
<tr>
<th style="text-align: center;"></th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: center;"><a href="https://i.sstatic.net/WoY0j.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WoY0j.png" alt="enter image description here" /></a></td>
</tr>
</tbody>
</table>
</div>
<p>Peripheral drift illusions, as their name suggests, create the illusion of motion in the periphery of the visual field. Similar images that generate illusory motion in the center of the visual field have been termed <a href="http://www.psy.ritsumei.ac.jp/%7Eakitaoka/VSJ04w.html" rel="nofollow noreferrer">central drift illusions</a>. Both of these types of illusions use high contrast &quot;luminance gratings&quot; - repeating patterns of high and low brightness - to generate illusory motion.</p>
<p>The cause of motion illusion in general is <a href="https://www.liveabout.com/why-do-these-still-images-appear-to-move-4864026" rel="nofollow noreferrer">not well understood</a>, but research suggests that there may be <a href="https://doi.org/10.3758/s13414-011-0131-9" rel="nofollow noreferrer">slightly different reasons</a> for the different types of motion illusions.</p>
<p>The dominant explanation for peripheral drift illusions in particular is that high-contrast colours have slightly different processing latencies at the retina, and as a result, neural signals arrive at the visual cortex at slightly different times, causing the illusion of motion (eg, <a href="https://doi.org/10.1068%2Fp2825" rel="nofollow noreferrer">Faubert &amp; Herbert, 1999</a>; <a href="https://doi.org/10.1167/5.11.10" rel="nofollow noreferrer">Backus &amp; Oruç, 2005</a>).  Comparison of brain activity using fMRI between actually moving and apparently moving images shows similar activity in the visual cortex, supporting the assertion that the illusion is caused at the retina rather than at the visual cortex (<a href="https://doi.org/10.1162/jocn.2006.18.7.1174" rel="nofollow noreferrer">Larsen et al, 2006</a>).</p>
<p>Since the difference in processing latencies is effective only at image onset, maintenance of the illusion should be enhanced by small eye movements (eg, <a href="https://en.wikipedia.org/wiki/Saccade" rel="nofollow noreferrer">saccades</a>, <a href="https://en.wikipedia.org/wiki/Fixation_(visual)" rel="nofollow noreferrer">fixational eye movements</a>, <a href="https://en.wikipedia.org/wiki/Microsaccade" rel="nofollow noreferrer">microsaccades</a>, and blinks).  This is indeed what experiments suggest (eg, <a href="https://doi.org/10.1523/JNEUROSCI.5823-11.2012" rel="nofollow noreferrer">Otero-Millan, Macknik, &amp; Martinez-Conde, 2012</a>; <a href="https://doi.org/10.1167/8.10.16" rel="nofollow noreferrer">Kuriki et al, 2008</a>).</p>

CC BY-SA 4.0
2014-12-14T07:44:14.627Z
2022-08-16T12:42:18.630Z
2022-08-16T12:42:18.630Z
Arnon Weinberg
<p>I saw the image below on facebook. At first, I thought it's a GIF animation since it doesn't appear static but it turned out to be a static JPEG image and the apparent motion is caused by the brain. So why does my brain trick me into believing that there's something moving? Does the brain have a purpose to do this optical illusion?
<br/><br/><br/></p>

<p><img src="https://i.sstatic.net/fp895.jpg" alt="illusion"></p>

<vision><optical-illusion>
What's the explanation of this optical illusion where many coloured arcs radiate from a central point?
user5402
# What's the explanation of this optical illusion where many coloured arcs radiate from a central point?

(Asked by: username_0 on 2014-08-09)

I saw the image below on facebook. At first, I thought it's a GIF animation since it doesn't appear static but it turned out to be a static JPEG image and the apparent motion is caused by the brain. So why does my brain trick me into believing that there's something moving? Does the brain have a purpose to do this optical illusion?

![illusion](https://i.sstatic.net/fp895.jpg)

**Tags:** vision, optical-illusion


---

## 2 answers

### Answer by username_2 on 2014-12-14. Score: 12 | Accepted answer

This is a type of [illusory motion](http://en.wikipedia.org/wiki/Illusory_motion) (or motion illusion) called a [peripheral drift illusion](https://en.wikipedia.org/wiki/Peripheral_drift_illusion#Gallery):

|  |
| --- |
| [enter image description here](https://i.sstatic.net/WoY0j.png) |

Peripheral drift illusions, as their name suggests, create the illusion of motion in the periphery of the visual field. Similar images that generate illusory motion in the center of the visual field have been termed [central drift illusions](http://www.psy.ritsumei.ac.jp/%7Eakitaoka/VSJ04w.html). Both of these types of illusions use high contrast "luminance gratings" - repeating patterns of high and low brightness - to generate illusory motion.

The cause of motion illusion in general is [not well understood](https://www.liveabout.com/why-do-these-still-images-appear-to-move-4864026), but research suggests that there may be [slightly different reasons](https://doi.org/10.3758/s13414-011-0131-9) for the different types of motion illusions.

The dominant explanation for peripheral drift illusions in particular is that high-contrast colours have slightly different processing latencies at the retina, and as a result, neural signals arrive at the visual cortex at slightly different times, causing the illusion of motion (eg, [Faubert & Herbert, 1999](https://doi.org/10.1068%2Fp2825); [Backus & Oruç, 2005](https://doi.org/10.1167/5.11.10)). Comparison of brain activity using fMRI between actually moving and apparently moving images shows similar activity in the visual cortex, supporting the assertion that the illusion is caused at the retina rather than at the visual cortex ([Larsen et al, 2006](https://doi.org/10.1162/jocn.2006.18.7.1174)).

Since the difference in processing latencies is effective only at image onset, maintenance of the illusion should be enhanced by small eye movements (eg, [saccades](https://en.wikipedia.org/wiki/Saccade), [fixational eye movements](https://en.wikipedia.org/wiki/Fixation_(visual)), [microsaccades](https://en.wikipedia.org/wiki/Microsaccade), and blinks). This is indeed what experiments suggest (eg, [Otero-Millan, Macknik, & Martinez-Conde, 2012](https://doi.org/10.1523/JNEUROSCI.5823-11.2012); [Kuriki et al, 2008](https://doi.org/10.1167/8.10.16)).


---

### Answer by username_1 on 2015-03-08. Score: 3

Mark Changizi proposed another level of understanding this illusion based on the "Perceiving the Present" hypothesis. Here is the [explanation](http://news.discovery.com/human/evolution/optical-illusions-you-brain-way-ahead-130823.htm):

> Optical illusions are actually a result of our brains trying to
> predict the future. When light hits our retina, it takes about
> one-tenth of a second for our brain to translate that signal into
> perception. This neural delay makes our brains generate images of what
> it thinks the world will look like in one-tenth of a second. It's not
> always right.
>
> “Your brain is slow, so you need to basically create perceptions that
> correct for that delay,” said Changizi, director of human cognition at
> 2AI Labs.
>
> Creating an image of the very near future probably kept early humans
> alive because it kept them from bumping into dangerous objects or
> being attacked by a fast-moving predator.

To learn more about the "[Perceiving the Present" hypothesis](http://onlinelibrary.wiley.com/doi/10.1080/03640210802035191/full)


---

