Human brain's input bandwidth

Not sure the best way to ask this, but I’m wondering if there’s any reasonable guess or estimate for how quickly a given sense processes data in humans?

For the sake of simplicity, I’ll define that for vision as:

If I read 500 words-per-minute and remember everything I read, what’s my visual pathway’s bps?

Also, do the other senses differ appreciably in how much information they can process per unit of time? Is the brain the info bottleneck or the particular sensory modality?

I have to quible with your example. For one thing, when I am reading, I am still accepting (and filtering out) other visual stimulii besides the words. This means that the throughput is greater than the net words read. To remember everything you read, then you probably are using context, since memory doesn’t work the same as a scanner. A closer example might be how fast can you read through a list of random items and still pick out individual items. Even that would still be an incomplete comparison to simply scanning.

I would posit that your visual pathway can scan somewhere in the same range as fast as digital television, with finer resolution, clarity and breadth of field. No idea what sort of bandwidth that represents.

Without any cite to back me up, I’m going to say that our senses are the bottleneck, not the brain. It’s tough to quantify in terms of bps because our senses are anolog. But using at-hand technology we get:

•Eyes can possibly handle upwards of 25Mbps (based on DVD signal stream rate).
•Ears can process 3.5Mbps (I arbitrarily lowered that - the channel rate of the data stream is actually closer to 4.3Mbps but the ear doesn’t respond to much above 16Khz or below 50Hz).
•Smell - I have no idea how to quantify that because I can’t think of a digital medium in which scents can be recorded or stored.
•Taste - Same problem as smell.
•Touch - Seems to me this has got to be the slowest way for the brain to acquire data, but again I can’t think of a way that touch sensations can be digitized (haha- that’s punny!). I mean, we can’t “read” barcodes with our fingers, and even braille is analog.

•Eyes can possibly handle upwards of 25Mbps (based on DVD signal stream rate).

The eyes themselves do a fair amount of image processing so you don’t get that much info from your eyes. Plus if you change the DVD slightly I don’t think people will notice which implies to me that there is not 25Mbps of information.

Neurons have a maximum firing rate. They fire and there is some finite non zero time before they can fire again. Given this information and a good estimate on how many nerve fibers come from the eyes to the brain. Armed with this information (which somebody besides me will have to look up) you can get an upper bound of the bandwidth.

It seems to me that there is no real bottleneck for information going to the brain. Each sense goes to a different part of the brain. Bottlenecking could possibly happen at the ends of neurons where neurotransmitters are brought into play.

I’m guessing (and I’ve had a couple of drinks) that the input rate for eyes is probably fairly close to infinite. I only make this assumption based on the notion that it is very hard to “overload” your sense of sight. What would it take to do it? The flash of an atomic bomb, or the Sun? Not much else is going to have that effect.

What the brain does is cross-reference all the data brought to it by sensory input. And that, to me, is what makes us human. We are acutely aware of our surroundings where most, if not all other animals, are not. The way that the human brain ‘processes’ data cannot be compared to the way a computer ‘processes’ data.

Gazpacho’s method for determining an upper bound on sensory input seems to be the most promising one yet.

I don’t have any answers, but I’d like to respond to a few things in other posters’ replies.

Adam Yax seems to have confused values with data rate. It doesn’t take any more information to describe an extremely bright scene than it does any other scene, the “overload” there is not of the senses, but actual damage to the mechanism. As an example of overloading your visual system, I’d say trying to track 30 or so erraticly moving objects in a room lit only by a strobe light might do it.

While Attrayant is correct as far as I know in that there are no existing digital formats for smell or taste, that doesn’t mean we can’t estimate the amount of information we get from those senses. We could estimate the number of distinct molecules that we can detect (which is different from the information necessary to describe those molecules), then multiply that by the resolution (as in parts per million) and get a value that way. I do not have numbers, but we can estimate the total number of bits necessary for one signal. Of course, the number of signals per time is still up in the air. It’s hard to imagine rapidly changing scents or tastes.

I have some old technical papers on precisely this subject, but alas they are in storage and inaccessible. One particularly interesting article was entitled “The Aesthetic Potential of Sensory Modes” and extensively catalogued the bandwidth of the human sensorium. And a few surprising sensory modes came up too, like “persistence” (i.e. pinch some flesh hard for about 30 seconds and it will still sting after you remove the pressure). And then it charted out each mode and proposed new senses at each intersection (i.e. combine cold sensations with pressure).
But anyway, I was astonished at how LOW bandwidth most inputs were, particularly visual. It seems that most brain mechanisms are actually filtering mechanisms and not interpreting or pattern-seeking mechanisms. While a DVD may pour 25Mb/s at us, we filter out most of that data and mostly detect motion through edge sensing, etc.
Anyway, no hard answers here, I’ll have to see if I can dig up some of the hard data from my archives.

However, you are not conscious of more than an infinitessimal fraction of this according to the same book.