<p><strong>Short answer</strong><br>
The brain actively integrates and synchronizes sensory inputs, up to the point that it actually delays one modality to match it with another.</p>

<p><strong>Background</strong><br>
Your question is all about <strong>intersensory asynchrony</strong> and <strong>sensory integration</strong>. </p>

<p>A well-known example where the two stimulus modalities you mention in your question (light and sound) are perceived as separate, while they are in fact coming from the same event, is a thunder heard <em>after</em> lightning. This is caused by the fact that sound travels at a speed much slower than light, and hence a thunder can lag lightning by seconds (Fig. 1).</p>

<p><img src="https://i.sstatic.net/P4Q3J.png" alt="Thunder lightning"><br>
<sup>source: <a href="http://www.grc.nasa.gov/WWW/k-12/airplane/sound2.html" rel="nofollow noreferrer">NASA</a></sup></p>

<p>In many instances, however, a multimodal perception is actually perceived as being synchronous, while they are in fact offset in time due to differences in physical characteristics of the stimuli. Take the storm as an example - when it is far away, the thunder is perceptually dissociated from the lightning, because the sound lags the light by seconds. But when the thunderstorm is close enough, the auditory crack and visual lightning are perceived as synchronous, while in fact they are still offset because of the sound travelling so much slower than light. </p>

<p>So why does the brain sync perceptions into 1 event, and sometimes not? This has to do with the <strong>window of integration</strong>. <a href="http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf" rel="nofollow noreferrer">Vroomen and Keetels (2010)</a> conclude in their review on this topic that a stimulus asynchrony in the case of auditory beeps and visual flashes can be between <strong>25 and 50 ms</strong> and still be perceived as coming from the same event. </p>

<p>The window of integration between more complex stimuli can be much greater. For example, the window for <strong>speech and visual information</strong> can be as large as <strong>203 ms</strong>. Such large windows of integration point toward higher processes playing a role in the brain. Only temporal lags <strong>below 20 msec</strong> are expected to go <strong>unnoticed because of hard-wired limitations</strong> on the resolution power of the individual senses.</p>

<p>Hence, <a href="http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf" rel="nofollow noreferrer">Vroomen and Keetels (2010)</a> argue there must be <strong>higher processes</strong> at work in the brain that actively synchronize percepts that are offset in time, but seem to belong to one and the same event. One such mechanism is referred to as <em><a href="https://acousticengineering.wordpress.com/tag/ventriloquist-effect/" rel="nofollow noreferrer">temporal ventriloquism</a></em>, which means that a <em>perceptual modality is <strong>actively shifted in time</strong> to match it with another modality</em>. This effect is most pronounced in visual stimuli. Visual perceptions are in fact <em>actively adjusted in time</em> to match a sound or tactile stimulus. Likely visual percepts are shifted preferably by the brain, because the visual system is the slowest of all the senses.</p>

<p><sub><strong>Reference</strong><br>
<a href="http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf" rel="nofollow noreferrer">Vroomen &amp; Keetels, <em>Att Percept Psychophys</em> 2010; <strong>72</strong>(4): 871-84</a></sub></p>

CC BY-SA 4.0
2020-04-14T14:08:55.017Z
2020-04-14T14:21:17.833Z
2020-04-14T14:21:17.833Z
AliceD
<p>The synchronization of sensory information is called <a href="https://en.wikipedia.org/wiki/Multisensory_integration" rel="nofollow noreferrer">multisensory integration</a>:</p>

<blockquote>
  <p>Multisensory integration, also known as multimodal integration, is the
  study of how information from the different sensory modalities (such
  as sight, sound, touch, smell, self-motion, and taste) may be
  integrated by the nervous system.</p>
</blockquote>

<p>This is the most salient example of neural "<a href="https://en.wikipedia.org/wiki/Neural_binding" rel="nofollow noreferrer">binding</a>".</p>

<p>The examples provided are of "temporal binding" - eg, when you touch your nose and your toes at the same time, the signal from your toes takes much longer to reach your brain, and yet, you experience the simultaneity just fine.  However, binding encompasses all aspects of conscious experience, such as object recognition, motor response, language processing, decision-making, emotion, etc, all of which can happen at different times and in different parts of the brain, but yet be experienced as unitary.</p>

<p>The question of how this happens is called the <a href="https://en.wikipedia.org/wiki/Binding_problem" rel="nofollow noreferrer">binding problem</a>, or to be more specific:</p>

<blockquote>
  <p>Secondly, there is the <em>combination problem</em>: the problem of how
  objects, background and abstract or emotional features are combined
  into a single experience. The combination problem is sometimes called
  BP2.</p>
</blockquote>

<p>Many hypotheses have been proposed that you can read about on <a href="https://en.wikipedia.org/wiki/Binding_problem#Modern_theories" rel="nofollow noreferrer">Wikipedia</a>, and some <a href="https://en.wikipedia.org/wiki/Recurrent_thalamo-cortical_resonance#Temporal_binding" rel="nofollow noreferrer">neuroscientific hypotheses</a> as well, but in general, this problem is currently unsolved.</p>

<p>The inevitable corollary of neural binding is that our sense of the real-time present is mostly composed of events taking place in the recent past - sometimes referred to as the "<a href="https://en.wikipedia.org/wiki/Specious_present" rel="nofollow noreferrer">specious present</a>".  How far in the past, or more specifically, the "<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326640/" rel="nofollow noreferrer">temporal binding window</a>" is highly variable, differs between individuals, and is affected by mental disorders, training, etc.  It is also not so much a window as a probability distribution, but certainly extends to the hundreds of milliseconds.</p>

CC BY-SA 4.0
2020-04-14T18:49:21.720Z
2020-04-14T18:49:21.720Z
Arnon Weinberg
<p>I am not an expert (actually I am not even psychologist/neuroscientist or anything like it).My question is: </p>

<p>Since light and sound comes to, respectively, our eyes and ears at different times and "visual input" and "sound input" take different times to be processed (and as far as I know, even some traits of vision - like color, motion, shape - take different time to be processed), how does our brain gives rise to the counscious experience of simultaneity (in the case of actual simultaneity, of course)? </p>

<p>How do we experience this synchronization of stimulus (which, of course, can include others senses, like touch and proprioception)? What would be a time line of that? Because it makes a bit confuse. Aren't we experiencing reality in real time (except for the fact that stimulus take time to get to our senses)?</p>

<neuroscience><sensory-perception><time><stimulation>
Synchronization of perception of sensory information
Jp_
# Synchronization of perception of sensory information

(Asked by: username_0 on 2020-04-13)

I am not an expert (actually I am not even psychologist/neuroscientist or anything like it).My question is:

Since light and sound comes to, respectively, our eyes and ears at different times and "visual input" and "sound input" take different times to be processed (and as far as I know, even some traits of vision - like color, motion, shape - take different time to be processed), how does our brain gives rise to the counscious experience of simultaneity (in the case of actual simultaneity, of course)?

How do we experience this synchronization of stimulus (which, of course, can include others senses, like touch and proprioception)? What would be a time line of that? Because it makes a bit confuse. Aren't we experiencing reality in real time (except for the fact that stimulus take time to get to our senses)?

**Tags:** neuroscience, sensory-perception, time, stimulation


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## 2 answers

### Answer by username_1 on 2020-04-14. Score: 2

**Short answer**  
The brain actively integrates and synchronizes sensory inputs, up to the point that it actually delays one modality to match it with another.

**Background**  
Your question is all about **intersensory asynchrony** and **sensory integration**.

A well-known example where the two stimulus modalities you mention in your question (light and sound) are perceived as separate, while they are in fact coming from the same event, is a thunder heard *after* lightning. This is caused by the fact that sound travels at a speed much slower than light, and hence a thunder can lag lightning by seconds (Fig. 1).

![Thunder lightning](https://i.sstatic.net/P4Q3J.png)  
source: [NASA](http://www.grc.nasa.gov/WWW/k-12/airplane/sound2.html)

In many instances, however, a multimodal perception is actually perceived as being synchronous, while they are in fact offset in time due to differences in physical characteristics of the stimuli. Take the storm as an example - when it is far away, the thunder is perceptually dissociated from the lightning, because the sound lags the light by seconds. But when the thunderstorm is close enough, the auditory crack and visual lightning are perceived as synchronous, while in fact they are still offset because of the sound travelling so much slower than light.

So why does the brain sync perceptions into 1 event, and sometimes not? This has to do with the **window of integration**. [Vroomen and Keetels (2010)](http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf) conclude in their review on this topic that a stimulus asynchrony in the case of auditory beeps and visual flashes can be between **25 and 50 ms** and still be perceived as coming from the same event.

The window of integration between more complex stimuli can be much greater. For example, the window for **speech and visual information** can be as large as **203 ms**. Such large windows of integration point toward higher processes playing a role in the brain. Only temporal lags **below 20 msec** are expected to go **unnoticed because of hard-wired limitations** on the resolution power of the individual senses.

Hence, [Vroomen and Keetels (2010)](http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf) argue there must be **higher processes** at work in the brain that actively synchronize percepts that are offset in time, but seem to belong to one and the same event. One such mechanism is referred to as *[temporal ventriloquism](https://acousticengineering.wordpress.com/tag/ventriloquist-effect/)*, which means that a *perceptual modality is **actively shifted in time** to match it with another modality*. This effect is most pronounced in visual stimuli. Visual perceptions are in fact *actively adjusted in time* to match a sound or tactile stimulus. Likely visual percepts are shifted preferably by the brain, because the visual system is the slowest of all the senses.

**Reference**  
[Vroomen & Keetels, *Att Percept Psychophys* 2010; **72**(4): 871-84](http://www.researchgate.net/profile/Jean_Vroomen/publication/43535149_Perception_of_intersensory_synchrony_a_tutorial_review/links/0fcfd506d6effbeaa1000000.pdf)


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### Answer by username_2 on 2020-04-14. Score: 2

The synchronization of sensory information is called [multisensory integration](https://en.wikipedia.org/wiki/Multisensory_integration):

> Multisensory integration, also known as multimodal integration, is the
> study of how information from the different sensory modalities (such
> as sight, sound, touch, smell, self-motion, and taste) may be
> integrated by the nervous system.

This is the most salient example of neural "[binding](https://en.wikipedia.org/wiki/Neural_binding)".

The examples provided are of "temporal binding" - eg, when you touch your nose and your toes at the same time, the signal from your toes takes much longer to reach your brain, and yet, you experience the simultaneity just fine. However, binding encompasses all aspects of conscious experience, such as object recognition, motor response, language processing, decision-making, emotion, etc, all of which can happen at different times and in different parts of the brain, but yet be experienced as unitary.

The question of how this happens is called the [binding problem](https://en.wikipedia.org/wiki/Binding_problem), or to be more specific:

> Secondly, there is the *combination problem*: the problem of how
> objects, background and abstract or emotional features are combined
> into a single experience. The combination problem is sometimes called
> BP2.

Many hypotheses have been proposed that you can read about on [Wikipedia](https://en.wikipedia.org/wiki/Binding_problem#Modern_theories), and some [neuroscientific hypotheses](https://en.wikipedia.org/wiki/Recurrent_thalamo-cortical_resonance#Temporal_binding) as well, but in general, this problem is currently unsolved.

The inevitable corollary of neural binding is that our sense of the real-time present is mostly composed of events taking place in the recent past - sometimes referred to as the "[specious present](https://en.wikipedia.org/wiki/Specious_present)". How far in the past, or more specifically, the "[temporal binding window](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326640/)" is highly variable, differs between individuals, and is affected by mental disorders, training, etc. It is also not so much a window as a probability distribution, but certainly extends to the hundreds of milliseconds.


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