In "Kwantechizm", a relatively popular book written by a Polish physicist Andrzej Dragan, I read that chickens move their head so that they can see things that are not in motion, with the following comment:

(...) It is similar with humans, because our eye is built on a similar principle to that of a chicken's eye. But to avoid the need to bend the head, it has special muscles that make it vibrate quickly. It is only thanks to these vibrations that we can see anything. If someone does not believe, they can inject a special injection into their eye to relax the muscles and the eye will stop twitching and everything that is still around will become invisible. Only the things that will move by themselves will emerge from the complete blackness.

(translated using Google Translate)

Is that true? Which muscle could he be talking about?

  • 1
    $\begingroup$ I've moved your question here because it's not really about any sort of medical condition, but about the psychology/neuroscience of perception more generally. $\endgroup$
    – Bryan Krause
    Sep 15, 2022 at 20:45

2 Answers 2


Short answer
Eye musculature takes care of the movements of the eye, including microsaccades that prevent retinal fading (adaptation). If microsaccades are inhibited by inactivating the eye muscles, retinal images of still objects will rapidly fade. Moving objects will still be visible.

I think the author of 'Kwantechizm' is referring to microsaccades. As Bryan alludes to in the last last few lines of the answer, the eye adapts swiftly to stimuli. Like any sensory system, continuous stimulation causes the sensory system to become unresponsive because of adaptation. In case of the eye microsaccades are believed to prevent fading of still retinal images because of slight eye movements that cause the retinal image to shift around on the retina in a random fashion (Martinez-Conde et al., 20004). Although a hotly debated topic, research on retinal implants have yielded anecdotal supportive evidence.

The (now discontinued) Argus II device is used to treat blindness. It is implanted onto the retina and delivers electrical stimuli to the retina that are guided by a head-worn camera. Microsaccades from the eye do not affect the retinal image anymore and it is indeed been reported that Argus II users' retinal images (phosphenes) elicited by the implant fade rapidly over time (Stronks et al., 2012). Argus II users therefore need to actively scan the environment by making head turns.

Fading has been reported to be far less severe in alpha-AMS implant, which was placed below the retina and had the photosensitive elements build onto the retinal chip. It therefore operates without an external camera and hence the natural microsaccades take care of the fading.

The muscles taking care of saccades and microsaccades depicted in Fig. 2. If these are paralyzed, static images will indeed fade, but head movements can remedy this effect. Moving objects will indeed still be seen, as the retinal image glides over the retina.

Argus II
Fig. 1. Argus II system. Panel A: external parts, including the glasses mounted external camera. B: internal parts. source: Stronks & Dagnelie (2014)

eye musculature
Fig. 2. Eye musculature. source: Britannica

- Martinez-Conde et al., Nature Rev Neurosci (2004); 5: 229–40
- Stronks et al., IOVS (2013); 54(6): 3891-901
- Stronks & Dagnelie, Exp Rev Med Dev (2014); 11(1): 23–30


I don't think the author is referring to any particular muscle, they are referring to the behavior of saccadic eye movements or just saccades. The words "vibrate" or "twitch" are also not quite right, but I am assuming this is mostly a translation issue.

The idea is that you don't see the world by just facing your eyes straight ahead like a camera. Even when you're looking at, say, a face, your eyes don't just point at the middle of the face and stay there, rather your gaze shifts all over to different parts of the face. Your brain builds a mental image of the whole face from all these movements that you are not particularly conscious of.

Here's an example:

Saccades example

Image credits: By Original file: SpooSpa. Derivative: Simon Viktória - Derivative work from File:Face of SpooSpa.jpg, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=8711778

The black lines and points between are the path that someones eyes took while looking at a face. You'll see that they skip around especially to various features: the eyes, nose, and mouth, as well as around the edges.

These eye movements let you see everything in more detail: your vision is best at the fovea, so these movements position different parts of the world in front of you on your fovea in sequence. Your brain then simply remembers what the fovea saw, so instead of experiencing one small thing in focus and everything else as a blur, you have a full detailed picture of the world around.

The author is also referencing neural adaptation with the mention of moving stimuli: constant stimuli tend to be somewhat ignored by the brain, and even at the level of a single receptor you will see little response to constant stimuli, but big responses to changes. If you have a static scene and your eyes are fixed, there are no changes and so you would expect to have minimal neural activity. Moving stimuli, however, are always changing.


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