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It is well known that our working memory (in our brains) is limited to about 7 items, the magical number 7, + or - 2. This is the Miller's law.

(our working memory is not at all like the RAM of a computer; it is profoundly associative)

Do we have reasons to believe that aliens (or our descendants, in several hundred thousands years) with a brain no more than twice as big as ours would have a larger limit?

(my intuition would be that this limit is logarithmic in the size of the brain, but I cannot explain why; in that case the limit won't change much for a brain twice as big, and certainly won't jump to 15)

Of course, plugging a computer inside our brain does not count as a way to increase its working memory.

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  • $\begingroup$ Great question, Basile. I'm already trying to think of the implications of having a lot more access to attention items. It'll be on my mind for a while today. :) $\endgroup$ Feb 11, 2016 at 19:33

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Miller's law isn't quite as meaningful as it appears at first. It seems magic, especially given that seven is a prime number. Consider how wide 7 +/- 2 is... its 5-9. There's almost a factor of two there, and the variability is nearly half of the values we are measuring! When you look further, this numeric value is very hard to pin down:

Working memory is generally considered to have limited capacity. The earliest quantification of the capacity limit associated with short-term memory was the "magical number seven" suggested by Miller in 1956.[20] He claimed that the information-processing capacity of young adults is around seven simultaneous elements, which he called "chunks", regardless whether the elements are digits, letters, words, or other units. Later research revealed this number depends on the category of chunks used (e.g., span may be around seven for digits, six for letters, and five for words), and even on features of the chunks within a category. For instance, span is lower for long than short words. In general, memory span for verbal contents (digits, letters, words, etc.) strongly depends on the time it takes to speak the contents aloud, and on the lexical status of the contents (whether the contents are words known to the person or not).[21] Several other factors affect a person's measured span, and therefore it is difficult to pin down the capacity of short-term or working memory to a number of chunks. Nonetheless, Cowan proposed that working memory has a capacity of about four chunks in young adults (and fewer in children and old adults)

How much working memory you need is really not just a factor of brain size. It's also affected by the kinds of tasks you are doing, and how well equipped the rest of your brain is for the task. A Japanese monk might suggest you only need a working memory size of one, you just have to pick the right one thing.

In general, I would expect that this number would vary based on how effective it is to divide something important up into pieces. If the things a species cares about are very fluid, dividing it up may be ineffective, and one complex thought may work better. If the species is constantly keeping track of individual discrete things (like a dragon counting their gold), they may want to have more spaces for various counters, each of which handles simpler content.

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    $\begingroup$ Agreed. Also note that Miller's Law applies for conditions of low stress. As stress increases, the number of independent tasks we can successfully monitor decreases, with tunnel vision (1 task only) being the limiting case. $\endgroup$ Feb 15, 2016 at 1:48
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Of course.

Dunno about "several hundred thousand years" -- I am planning on getting the upgrade as soon as it becomes feasible to implement without destroying too much of my current personality.

If you think about it, it was a limitation induced by the fact that computation is expensive, and energy to run that computation is hard to get and subjects us to danger. If 7 items can ensure survival in an African plain 60,000 years ago, the humans with the capacity for 15 ideas would have had higher metabolic requirements and would have been out-competed by their less endowed cousins.

The environment we live in now is not under a severe basic resource constraint anymore (if anything we seem to be dealing with an overabundance of food problem in the undeniable fact of widespread obesity). Moreover, the computational substrate of computers will likely continue to increase in efficiency, and can be expected to eventually pass the human level of energy consumption (computations per Joule or whatever measure makes sense to you). The technical capability does not exist at the moment, but as gigantic strides are made in understanding human brains, the process to augment the number of attention items will move from impossible to exceedingly difficult, then simply hard, and finally trivial. Even if a number of countries implement anti-eugenic standards, the advantages to be gained from such enhancements are simply too great, and ruthlessly determined individuals will ignore the law to their benefit. It cannot be stopped.

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  • $\begingroup$ I'm pretty squeamish about various cybernetic upgrades (I'm terrified of going blind, so even modern laser eye correction makes be shiver), but installing more memory in my brain? I'd be first in line. Well. Not first, but you know, safety and all that. First in line in the consumer market. $\endgroup$ Feb 11, 2016 at 20:04
  • $\begingroup$ My understanding of our working memory is that it does not at all work lilke RAM memory in our laptops. It is a deeply associative memory. $\endgroup$ Feb 11, 2016 at 20:06
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    $\begingroup$ @BasileStarynkevitch "Is there any risk of something like brain damage?" "Well, technically, the procedure is brain damage." --Eternal Sunshine of the Spotless Mind $\endgroup$ Feb 11, 2016 at 20:10
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I would expect if anything for biological working memory to decrease, this is because more and more we're offloading processing to computers. For example trained (human) calculators a century ago could do mathematics by hand and by slide rule far faster than virtually anyone alive today could simple because they needed to and practiced it a lot.

These days you'd drop the numbers into a spreadsheet and be done.

Facebook already remembers everyone's birthday for you. Your phone remembers everyone's phone number, etc. When's the last time you had to memorize someone's number for long enough to get home and write it down? I remember my mum doing that but I've never had to.

Some highly trained individuals will no doubt have skills that seem extreme to us now, in the same way the olympic athletes are just as good or better as those from centuries ago. The gap between the trained elite and everyone else will get wider though just as the fitness level gap is.

However the odds are pretty good that at some point or mobile phones will be directly interfacing with our brains ... and at that point it becomes really hard to separate our working memory and the phone's...

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