Brain size does not directly correlate with intelligence. Intelligence is still poorly understood. Also, there are different types of intelligence. All of them rely on using different areas of the brain in different ways.

A lot of the brain just process information from the body and don't have anything to do with your conscious thought. People with larger bodies need larger brains, especially people with larger eyes but peoples eyes are mostly the same size.

Also what we think of as intelligence is mostly determined by personality. If your brain works 10% faster then average you are just going to spend about 9% less time thinking up the same mediocre idea that someone else with the same personality would until you think, good enough.

I don't think we have a definitive answer to this, but from my understanding intelligence within a species has less to do with the brain's size and more to do with it's structure and complexity. Also, someone who is born bigger and taller won't necessarily be faster or stronger if they don't do at least equal amounts of exercise. Similarly, someone born with a higher potential for intelligence won't be smarter if they don't do things like read, create, scrutinize, and solve problems. Another likely reason is that a person born with a gifted physique might be more inclined to nurture that aspect of themselves, e.g. choosing to go to the gym rather than the library.

Sperm whales have the biggest brain of any creature but they are not the most intelligent creature. We aren't sure why, but brain to body ratio seems to correlate with intelligence. If a person is 40% larger, but their brain is also only 40% larger, then they aren't likely to be more intelligent.

the size of a human brain has nothing to do with the size of the body or skull it's housed in. the same goes for the penis, heart, etc.

muscles, and body mass, have no correlation to the size of a person's brain. neurological development has more to do with experience.

Taller people aren’t automatically stronger. Depends on how much you exercise the muscles, and your brain is just another muscle that needs conditioning.

You're basically talking about phrenology. Been debunked. And bigger body =/= stronger. Many people who are very tall (or very short) tend to have a lot more health problems because of it, with Andre the Giant being a good example.

You have people that had their brain compressed to half its size by fluids and they were perfectly fine. Intelligence is more about connectivity between neurons, epigenetics and ability to solve problems in current situations than absolute number of neurons.

Intelligence is mostly attributable to environmental components and physiological components.

Environmental: exposure to stimuli, access to resources, how much lead you were exposed to as a child, and your network of family, friends, and the community who helped you gain your intelligence.

Physiological: the number of neural connections your brain has, the speed in which you can recall info, the speed/efficiency in which you can retain info, your ability to apply the information that you have to other scenarios, your ability to detect patterns, the speed in which your neurons can pass info to each other, the number of teratogens you were exposed to in utero, the intelligence of your parents – although that is probably more an environmental component than a biological one.

Anyway, there are numerous components that affect intelligence, but the size of the brain isn't really one of them. There are notable individuals who are considered above average intelligence and who were also born with only one hemisphere of their brain. Size doesn't matter much just like the size of a car doesn't predict how fast it will run.

Neurons don't mean shit in isolation; what matters is neural connections (AKA synapses). When you're a tiny baby, first you make a ton of synapses, and then you get rid of a huge number of unused ones and make the most useful synapses efficient and well-connected; this "efficient, well-connected" structure is why you're smarter than a two year old (as opposed to more sensible or knowledgeable).

Think about your brain like a computer: a laptop model having a few percent more space to install a big CPU is okay, but the quality of the code it runs will have vastly more say in how fast the computer actually is.

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