<h3>Preface</h3>

<p>This is a very interesting question, that is also somewhat related to my area of research. I know of several related results (which I might add later in an edit), and I thought that with a few minutes of scholar search I'll find a paper dealing with this question exactly. I was surprised to find no such papers. So I decided to conduct an experiment...</p>

<h2>Answer (preliminary. hopefully, will be edited)</h2>

<p>As with many cases in psychology, the <strong>threshold</strong> is completely non-existant: there is no delay up to which the reaction is perceived as instantaneous, and after which it is perceived as delayed. You can measure the probability of the subject perceiving a delay, as a function of the delay time. You can choose any probability you want, arbitrarily, and call it the 'threshold'. If we decide on 50% (the chance of responding there was a delay is identical to the chance of responding it was instantaneous) then for me it is about <strong>110ms</strong>.</p>

<p><img src="https://i.sstatic.net/hLfpP.png" alt="results of preliminary experiment on 1 subject, myself"></p>

<p>The results presented here are based on 100 trials, performed by myself. Hardly counts as good study, but if a few more people run the test, I promise to process the results and post them here (and who knows, maybe even publish it somewhere :))</p>

<h2>To participate in the experiment yourself</h2>

<ul>
<li>Sign up to <a href="http://ofri.webfactional.com" rel="noreferrer">ofri.webfactional.com</a>. (It is a site I developed for web-based experiments conducted in my lab. It's still in beta, which is why its under a domain with my name, and not under huji.ac.il.  I promise we do not use your email for anything except for identifying you. No spam ever).</li>
<li>In the <strong>Group Name</strong> field in the registration, enter <strong>instant</strong>.</li>
<li>Login, and follow the on-screen instructions. Its really simple.</li>
<li>After running more than 60 trials another button will appear with the text 'show results'. Clicking it will draw a graph similar to the one presented here, based on your personal results.</li>
</ul>

CC BY-SA 3.0
2012-09-21T23:02:01.510Z
2012-09-21T23:02:01.510Z
Ofri Raviv
<p>In Human Computer Interaction and User Experience there's some <a href="http://www.useit.com/papers/responsetime.html" rel="noreferrer">oft repeated rules of performance</a>:</p>
<blockquote>
<ul>
<li><strong>0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.</strong></li>
<li>1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay....</li>
<li>10 seconds is about the limit for keeping the user's attention focused on the dialogue...</li>
</ul>
</blockquote>
<p>I'm most interested in this &quot;instantaneous&quot; response. Related is this <a href="https://ux.stackexchange.com/questions/16253/defining-instantaneous-as-part-of-usability-acceptance-criteria">User Experience Question</a>. <a href="https://ux.stackexchange.com/a/4/7627">A related answer does bring up some sources</a>:</p>
<blockquote>
<p>Card, S. K., Robertson, G. G., and Mackinlay, J. D. (1991). The information visualizer: An information workspace. Proc. ACM CHI'91 Conf. (New Orleans, LA, 28 April-2 May), 181-188.</p>
<p>Miller, R. B. (1968). Response time in man-computer conversational transactions. Proc. AFIPS Fall Joint Computer Conference Vol. 33, 267-277.</p>
<p>Myers, B. A. (1985). The importance of percent-done progress indicators for computer-human interfaces. Proc. ACM CHI'85 Conf. (San Francisco, CA, 14-18 April), 11-17.</p>
</blockquote>
<p>However I can't access any copies of those articles. Also, frankly, they're all <em>conference papers</em>. Big HCI research often debuts at conferences, but ideally I'd like something robust which has been tested rather than something written 20-40 years ago for a conference.</p>
<p>One thing I've noticed is the &quot;instant response&quot; threshold quoted tends to be around 100ms to 200ms. Typical human reaction time is about 200ms so I'm wondering if there is a relation there. It seems possible; if something happens so quickly you can't <em>react</em> to it, it is practically &quot;instant&quot; in a way.</p>
<p><strong>Approximately what length of time between action and reaction is perceived as instant by humans?</strong></p>

CC BY-SA 3.0
2012-09-18T19:16:20.270Z
This question was inspired by [Defining “Instantaneous” as part of usability acceptance criteria](http://ux.stackexchange.com/questions/16253/defining-instantaneous-as-part-of-usability-acceptance-criteria) over on [ux.se]
Zelda
CC BY-SA 3.0
2013-03-15T23:33:45.473Z
Side note: CHI is not like most conferences. They are an "archival" publication and have strict rules about the originality of content. While many researchers treat conferences as a stepping stone to a journal publication, CHI is often the end of the line for research in HCI.
Jeff
CC BY-SA 4.0
2018-12-06T18:48:38.887Z
Apple has a WWDC video called Designing Fluid User Interfaces with a neat demo of latency in swipe gestures: https://developer.apple.com/videos/play/wwdc2018-803/?time=352 (you may need a (no-cost) Apple Developer Account to view it).
Frank Schmitt
<perception><measurement><time><hci>
What is the threshold where actions are perceived as "instant"?
Zelda
# What is the threshold where actions are perceived as "instant"?

(Asked by: username_0 on 2012-09-18)

In Human Computer Interaction and User Experience there's some [oft repeated rules of performance](http://www.useit.com/papers/responsetime.html):

> * **0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.**
> * 1.0 second is about the limit for the user's flow of thought to stay uninterrupted, even though the user will notice the delay....
> * 10 seconds is about the limit for keeping the user's attention focused on the dialogue...

I'm most interested in this "instantaneous" response. Related is this [User Experience Question](https://ux.stackexchange.com/questions/16253/defining-instantaneous-as-part-of-usability-acceptance-criteria). [A related answer does bring up some sources](https://ux.stackexchange.com/a/4/7627):

> Card, S. K., Robertson, G. G., and Mackinlay, J. D. (1991). The information visualizer: An information workspace. Proc. ACM CHI'91 Conf. (New Orleans, LA, 28 April-2 May), 181-188.
>
> Miller, R. B. (1968). Response time in man-computer conversational transactions. Proc. AFIPS Fall Joint Computer Conference Vol. 33, 267-277.
>
> Myers, B. A. (1985). The importance of percent-done progress indicators for computer-human interfaces. Proc. ACM CHI'85 Conf. (San Francisco, CA, 14-18 April), 11-17.

However I can't access any copies of those articles. Also, frankly, they're all *conference papers*. Big HCI research often debuts at conferences, but ideally I'd like something robust which has been tested rather than something written 20-40 years ago for a conference.

One thing I've noticed is the "instant response" threshold quoted tends to be around 100ms to 200ms. Typical human reaction time is about 200ms so I'm wondering if there is a relation there. It seems possible; if something happens so quickly you can't *react* to it, it is practically "instant" in a way.

**Approximately what length of time between action and reaction is perceived as instant by humans?**

**Tags:** perception, measurement, time, hci

> **Comments:**
> **username_0**: This question was inspired by [Defining “Instantaneous” as part of usability acceptance criteria](http://ux.stackexchange.com/questions/16253/defining-instantaneous-as-part-of-usability-acceptance-criteria) over on [ux.se]  
> **username_1**: Side note: CHI is not like most conferences. They are an "archival" publication and have strict rules about the originality of content. While many researchers treat conferences as a stepping stone to a journal publication, CHI is often the end of the line for research in HCI.  
> **username_2**: Apple has a WWDC video called Designing Fluid User Interfaces with a neat demo of latency in swipe gestures: https://developer.apple.com/videos/play/wwdc2018-803/?time=352 (you may need a (no-cost) Apple Developer Account to view it).  

---

## 1 answers

### Answer by username_3 on 2012-09-21. Score: 15

### Preface

This is a very interesting question, that is also somewhat related to my area of research. I know of several related results (which I might add later in an edit), and I thought that with a few minutes of scholar search I'll find a paper dealing with this question exactly. I was surprised to find no such papers. So I decided to conduct an experiment...

## Answer (preliminary. hopefully, will be edited)

As with many cases in psychology, the **threshold** is completely non-existant: there is no delay up to which the reaction is perceived as instantaneous, and after which it is perceived as delayed. You can measure the probability of the subject perceiving a delay, as a function of the delay time. You can choose any probability you want, arbitrarily, and call it the 'threshold'. If we decide on 50% (the chance of responding there was a delay is identical to the chance of responding it was instantaneous) then for me it is about **110ms**.

![results of preliminary experiment on 1 subject, myself](https://i.sstatic.net/hLfpP.png)

The results presented here are based on 100 trials, performed by myself. Hardly counts as good study, but if a few more people run the test, I promise to process the results and post them here (and who knows, maybe even publish it somewhere :))

## To participate in the experiment yourself

* Sign up to [ofri.webfactional.com](http://ofri.webfactional.com). (It is a site I developed for web-based experiments conducted in my lab. It's still in beta, which is why its under a domain with my name, and not under huji.ac.il. I promise we do not use your email for anything except for identifying you. No spam ever).
* In the **Group Name** field in the registration, enter **instant**.
* Login, and follow the on-screen instructions. Its really simple.
* After running more than 60 trials another button will appear with the text 'show results'. Clicking it will draw a graph similar to the one presented here, based on your personal results.


---

