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Do all humans have the same visual processing speed or not?

  1. Jul 30, 2017 #1
    Do all humans have the same visual processing speed or does it differ from person to person?

    By ‘visual processing speed’, I mean the speed at which one takes to process visual information. For example, if a light has a frequency of 50 hertz where it switches on / off 50 times a second, do all humans have the same limit to how many hertz of the light switching on / off they can process?

    Another example is RPM of a spinning wheel where something is written on that wheel. Do all humans have the same maximum limit at the RPM in which they can process the written text at?

    Or something appearing in a computer screen in a specific time interval, such as miliseconds. Do all humans have the same limit in the smallest time interval they can all process the written data appearing in the screen at or does it differ?
     
    Last edited by a moderator: Jul 30, 2017
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  3. Jul 30, 2017 #2

    scottdave

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    It looks like different people will have different reactions. Also, a person's reaction will change as he/she ages. Check out this video from SmarterEveryDay. At about 5:20 he talks to an expert in visual perception.


    Notice the difference between a fluorescent light fixture and incandescent. The filament of the incandescent doesn't have time to cool down much between the nodes of the 50 or 60 Hz cycle (depending on where you live). So the incandescent appears smoother.
     
  4. Jul 30, 2017 #3

    jim mcnamara

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    This topic is actually advanced neuroscience.

    See what a saccade is: https://en.wikipedia.org/wiki/Saccade
    In order for humans to recognize something it may require saccades - eye movements. Drugs, age, trauma, alcohol, and disease process all affect this aspect of recognition.

    So it is not a simple straightforward 'how long does it take to see something' kind of deal. A lot is going on.

    This discusses measuring with imposed controlled conditions - in other words trying to minimize (hopefully remove) the effect of eye movements in speed of perception tests.

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4667031/

    There are other members who know much more about this field than I do. Hopefully they will see the thread and help us.
     
  5. Jul 30, 2017 #4

    scottdave

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    I am confident in saying that "all humans do not have the same visual processing speed". As far as being able to "see" 50 Hz, though. That may be a stretch. Consider this: Movies typically would run at 24 frames per second. For the most part, people seemed to think this was smooth enough.
     
  6. Jul 31, 2017 #5

    Drakkith

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    I can tell the difference between my computer games running at 30 FPS vs when they are running at 120+ FPS. I'm not sure where I stop noticing any difference, but I'm confident that 24 HZ is a "bare minimum" for most people to comfortably view a video without perceiving the motion as unduly jerky or stuttery or however you want to say it.
     
  7. Jul 31, 2017 #6

    scottdave

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    So I figured that they would want to get the minimum number of frames per second, without getting complaints from customers.

    According to this Wikipedia article https://en.wikipedia.org/wiki/Frame_rate the minimum acceptable, which Edison determined, was 46 frames per second. So they had two blade shutters, effectively showing each frame twice and getting 48 flashes per second (or some even had 3 blades for 72). Even though it was the same frame flashed multiple times, the higher flash rate resulted in a more pleasing experience. The article also discussed that there was little consistency, with cameras originally hand cranked, and some theaters ran speeds between 22 and 26 frames per second. When they started having sound films, a standard was needed, so they would sound the same. It was an interesting article.
     
  8. Jul 31, 2017 #7

    BillTre

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    From a video course I had recently, I would agree that 24 FPS is close to the minimum to get a non-jerky movie effect, which is way that standard was established when movies were first made.

    I agree with @jim mcnamara that it is really a complex neuro-perceptual problem. the first step would be to experimentally define what you will be using as the visual process to measure. You would also have to define how much variability you would accept before you would say the response time was different.

    I would also expect, as @scottdave said, that everyone's speed would vary somewhat.
    Each synapse (connection between neurons) would take about 2 ms for a signal to cross. This is the major, but not only time delay. How an individual neuron will add up its synaptic inputs and decide to make a new action potential can vary depending on the strength of the incoming signals. There are many synapses involved before the signal reaches consciousness (which is not well defined). Cortical areas can vary between individuals, so processing steps could also vary.
     
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