Question about brain size.

[apathy]

We are shown ancient humanoid skulls and are told that cranial capacity increased as humans evolved. It is also inferred that this increase in brain size corresponds to an increase in intellegence and learning ability.

 

But, certain animals, like domestic dogs, come in all shapes and sizes. A very small dog with a small brain can often be more intellegent than a large dog with a large brain. This would tell me that the dog's intellegence has more to do with "wiring" than size.

 

Also, some parrots have demostrated the ability to learn concepts and adapt them to speech. Not just "parroting" but answering questions like "what color is this?" "green" and their brains are no larger than a peanut and not specifically wired for human-like speech.

 

Could someone please explain this to me?

[LucidDreamer]

Good question. One key to this is that its not the brain size that matters so much as the brain to body ratio. The sperm whale has a brain much larger than ours but its brain to body ratio is smaller. Dog brains probably vary in size just like human brains. In fact one person's brain can weigh twice as much as another person’s brain and both can still be perfectly normal. Parrots can be taught to reply to certain human phrases and gestures just like dogs. A parrot responding to "what color is this" is similar to a dog barking once, twice, or three times depending on what command you give him. But neither one ever wonders why something is green.

[Glider]

Our skull capacity increased to cope with the relatively sudden increase in the size of the human neocortex. This was the last 'part' of the brain to evolve and in humans, is much more developed than in other animals. Our cortex is 'pleated' to increase the overall area that can fit into our skulls (gyri = outward folds. sulci = inward folds). Between species, there is a relationship between the number of gyri and intelligence (i.e. between overall neocortical area and intelligence).

[ydoaPs]

the discovery channel said that it was the number of connections that determines intelligence, not size. sorry, but i do not remember which program

[apathy]

well, i didn't expect to get answers that were that good

thanks a lot! it makes more sense to me now

 

i suspected that it had a lot to do with brain size to body size ratio, since I have heard that the brains of wolves are proprotionally larger than those of domestic dogs because they have more to remember about their social order and hunting strategy, etc. while domestic dogs were thought to have originally been slightly social scavengers (at least this is what I've read in mags)

 

this is still implying that brain size has something to do with intellegence, even if it's relative brain size

 

about the neocortex and gyri:

is there such a strong relationship between the number of gyri and intellegence?

i mean if we cracked open the skull of a genius and one of a person considered "slow" could we count a difference in gyri? or is it just an average difference across species?

 

and this is saying that the size (or relative size) of a certain part of the brain has to do with intellegence

 

i can see that intellgence must have something to do with the presence of the neocortex, this says that the 'wiring' is important, of course

 

then increased intellegence comes from an increase the relative size of this part?

 

does more intellegence stem from having more neurons? bigger neurons?

i'm trying not to oversimplify it, but it's tough

[Cap'n Refsmmat]

What matters is brain size compared to body size.

[apathy]

woops

that last post from yourdad... got in there before i hit "post"

[apathy]

more connections makes sense to me

[LucidDreamer]

I believe that a lot of the differences in intelligence among human beings has to do with the chemistry of the brain, not just the physical hardwiring. I believe that you may be right about someone who has great intelligence having more connections. Someone like Einstein probably had more connections and glial cells because he was both born with greater capacity to develop them and because he spent his whole life learning and experimenting.

[Glider]

about the neocortex and gyri:

is there such a strong relationship between the number of gyri and intellegence?

i mean if we cracked open the skull of a genius and one of a person considered "slow" could we count a difference in gyri? or is it just an average difference across species?

 

and this is saying that the size (or relative size) of a certain part of the brain has to do with intellegence

 

i can see that intellgence must have something to do with the presence of the neocortex' date=' this says that the 'wiring' is important, of course

 

then increased intellegence comes from an increase the relative size of this part?

 

does more intellegence stem from having more neurons? bigger neurons?

i'm trying not to oversimplify it, but it's tough[/quote']

It is tough. As far as I know, the relationship between gyri and intelligence is a relative one, across species. I seem to remember there was some investigation into the number and relative complexity of gyri and sulci in humans, comparing the brains of 'normals' with the brains people with congenital learning disorders and idiocy, but I can't remember the specifics.

 

The dominant view is that wiring and number of synapses is the critical factor in intelligence, as most neurological phenomena appear to be a function of circuitry, rather than the activity of any particular area(s). This makes sense, as a significant factor in intelligence is the ability to make connections between apparently unrelated pieces of information.

 

Wiring relates to size to some degree, or at least to area (ask a circuit board designer). So, to some degree, the size of the cortex is a factor. The overall area of the cortext has to be larger the more connections there are between different parts of it (the cortex is only 6 neurons deep, so really, it is like a thin sheet, 'scrunched up' to fit like a cap over the limbic brain). So, the larger the cortex, the greater the number of convolutions needed to allow it to fit within the skull.

 

However, the above, poorly remembered study notwithstanding, within a group (e.g. humans) brain size makes little difference to intelligence. For example, the brains of women get smaller when they are pregnant, but they don't lose intelligence.

[Europa]

Hello,

 

I will also support the claim that at least in humans, it's the brain size to body size ratio that has .44 correlation to IQ, as is stated at http://www.udel.edu/educ/gottfredson/reprints/1998generalintelligencefactor.pdf

 

"Moreover, research on the physiology and genetics of g has uncovered biological correlates of this psychological phenomenon. In the past decade, studies by teams of researchers in North America and Europe have linked several attributes of the brain to general intelligence. After taking into account gender and physical stature, brain size as determined by magnetic resonance imaging is moderately correlated with IQ (about 0.4 on a scale of 0 to 1). So is the speed of nerve conduction. The brains of bright people also use less energy during problem solving than do those of their less able peers. And various qualities of brain waves correlate strongly (about 0.5 to 0.7) with IQ: the brain waves of individuals with higher IQs, for example, respond more promptly and consistently to simple sensory stimuli such as audible clicks. These observations have led some investigators to posit that differences in g result from differences in the speed and efficiency of neural processing."

[apathy]

wow, cool

 

from these responses I definitley understand much better now

 

it seems that there are many factors (as to be expected) that influence intellegence

and it even seems that brain size may be one of them (but not at all the major one)

 

i never thought there may be a difference in nerve conduction among individuals

 

maybe the people whose brain waves are "high quality" , or more efficient anyway, have a more well-constructed "schema" or something like that, that may have stemmed from early childhood development? maybe they were more mentally stimulated in the early years of childhood? that would tend to compliment the genetic side of things a little i suppose

 

anyway, i feel much more informed about it...

thanks again!