<p>Pupil dilation is a reflection of sympathetic arousal, and it seems to be related specifically to <strong>prediction error</strong> (<a href="http://link.springer.com/article/10.3758/s13415-014-0333-4" rel="nofollow">Braem et al., 2015</a>; <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3879532/" rel="nofollow">Lavin et al., 2013</a>; <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183372/" rel="nofollow">Preuschoff et al., 2011</a>) and consequently predicts your learning rate (<a href="http://www.nature.com/neuro/journal/v15/n7/full/nn.3130.html%3FWT.ec_id%3DNEURO-201207?message-global=remove&amp;WT.ec_id=NEURO-201207" rel="nofollow">Nassar et al., 2012</a>).</p>

<p>In the case where you see an attractive person amidst a sea of average faces, this violates your predictions--you have prediction error (or "surprise").  You expected to see an average face, not an attractive face, and your pupils dilate in response.  If you are continually exposed to this attractive person, your pupil dilation will decrease over time.</p>

<p>This is true with emotions more generally--when you feel negative or positive this usually indicates prediction error (or success), which then up- or downregulates your learning rate, respectively (e.g., <a href="http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1003094" rel="nofollow">Joffily &amp; Coricelli, 2013</a>).</p>

<p><strong>Why is pupil dilation associated with prediction error?</strong>  The sphincter (contracts the eye) and dilator (dilates the eye) are innervated by acetylcholine and noradrenaline, respectively. Noradrenergic activity in the locus coeruleus might encode "unexpected uncertainty," which interacts with antagonistic cholinergic activity.  Interestingly, dilating the pupil on one task can increase the learning rate on another, unrelated task (<a href="http://www.nature.com/neuro/journal/v15/n7/full/nn.3130.html%3FWT.ec_id%3DNEURO-201207?message-global=remove&amp;WT.ec_id=NEURO-201207" rel="nofollow">Nassar et al., 2012</a>), which might be mediated by incidental activation of noradrenergic activity in the locus coeruleus.</p>

<p>Hmmmm, I don't actually seem to know enough about this such that I can explain all of it clearly! But hopefully this provides some insight into your question.</p>

CC BY-SA 3.0
2016-01-19T00:24:59.780Z
2016-01-19T00:31:59.297Z
2016-01-19T00:31:59.297Z
mrt
<p>The dilation of the pupil is under control of the sympathetic nervous system. The main role of the sympathetic nervous system is to get the body ready for fast response. The typical example is the 'fight-or-flight' response, but that can also occur in the presence of a potential sexual partner. Therefore, dilated pupils can be a sign of sexual arousal. 
Now, that's the response of the person showing the dilated pupils, but your question related to the effect on the other person. People with more dilated pupils are rated as more attractive by observers unaware of this manipulation <a href="http://www.sciencedirect.com/science/article/pii/S1090513804000261" rel="nofollow">Tombs &amp; Silverman, 2004</a> - at least for males looking at females. As an aside, people in ancient Egypt are said to have used atropine, which is a poison extracted from the belladonna plant, as a cosmetic to artificially dilate their pupils. </p>

CC BY-SA 3.0
2016-01-18T19:31:53.950Z
2016-01-18T19:31:53.950Z
Joe Bathelt
<p>I just came across an <a href="http://www.omgfacts.com/nerd/8434/Your-pupils-dilate-when-you-see-someone-attractive">article</a> on the internet stating that,</p>

<blockquote>
  <p>Pupils dilate when we find someone or something attractive.</p>
</blockquote>

<p>So, as far as I know, this kind of dilation doesn't seem to have any effect on attractiveness of subject, does it?</p>

<p><strong><em>For example:</em></strong></p>

<p>Suppose if a one person A in love with person B, and pupils of A tend to dilate when seeing B, What effect does it have on B? Any psychological effect perhaps?</p>

<p>P.S. I'm not sure if this should be on Cog.Sci</p>

<psychology>
Why do pupils dilate in response to emotional state?
Snazzy Sanoj
# Why do pupils dilate in response to emotional state?

(Asked by: username_0 on 2016-01-18)

I just came across an [article](http://www.omgfacts.com/nerd/8434/Your-pupils-dilate-when-you-see-someone-attractive) on the internet stating that,

> Pupils dilate when we find someone or something attractive.

So, as far as I know, this kind of dilation doesn't seem to have any effect on attractiveness of subject, does it?

***For example:***

Suppose if a one person A in love with person B, and pupils of A tend to dilate when seeing B, What effect does it have on B? Any psychological effect perhaps?

P.S. I'm not sure if this should be on Cog.Sci

**Tags:** psychology


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## 2 answers

### Answer by username_2 on 2016-01-18. Score: 4 | Accepted answer

The dilation of the pupil is under control of the sympathetic nervous system. The main role of the sympathetic nervous system is to get the body ready for fast response. The typical example is the 'fight-or-flight' response, but that can also occur in the presence of a potential sexual partner. Therefore, dilated pupils can be a sign of sexual arousal.
Now, that's the response of the person showing the dilated pupils, but your question related to the effect on the other person. People with more dilated pupils are rated as more attractive by observers unaware of this manipulation [Tombs & Silverman, 2004](http://www.sciencedirect.com/science/article/pii/S1090513804000261) - at least for males looking at females. As an aside, people in ancient Egypt are said to have used atropine, which is a poison extracted from the belladonna plant, as a cosmetic to artificially dilate their pupils.


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### Answer by username_1 on 2016-01-19. Score: 4

Pupil dilation is a reflection of sympathetic arousal, and it seems to be related specifically to **prediction error** ([Braem et al., 2015](http://link.springer.com/article/10.3758/s13415-014-0333-4); [Lavin et al., 2013](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3879532/); [Preuschoff et al., 2011](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3183372/)) and consequently predicts your learning rate ([Nassar et al., 2012](http://www.nature.com/neuro/journal/v15/n7/full/nn.3130.html%3FWT.ec_id%3DNEURO-201207?message-global=remove&WT.ec_id=NEURO-201207)).

In the case where you see an attractive person amidst a sea of average faces, this violates your predictions--you have prediction error (or "surprise"). You expected to see an average face, not an attractive face, and your pupils dilate in response. If you are continually exposed to this attractive person, your pupil dilation will decrease over time.

This is true with emotions more generally--when you feel negative or positive this usually indicates prediction error (or success), which then up- or downregulates your learning rate, respectively (e.g., [Joffily & Coricelli, 2013](http://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1003094)).

**Why is pupil dilation associated with prediction error?** The sphincter (contracts the eye) and dilator (dilates the eye) are innervated by acetylcholine and noradrenaline, respectively. Noradrenergic activity in the locus coeruleus might encode "unexpected uncertainty," which interacts with antagonistic cholinergic activity. Interestingly, dilating the pupil on one task can increase the learning rate on another, unrelated task ([Nassar et al., 2012](http://www.nature.com/neuro/journal/v15/n7/full/nn.3130.html%3FWT.ec_id%3DNEURO-201207?message-global=remove&WT.ec_id=NEURO-201207)), which might be mediated by incidental activation of noradrenergic activity in the locus coeruleus.

Hmmmm, I don't actually seem to know enough about this such that I can explain all of it clearly! But hopefully this provides some insight into your question.


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