Just because you can do something doesn't mean you will or should do it. Yes, intelligence probably helps with manipulation. Just like it helps you become a better murderer, yet it has nothing to do with whether someone's going to be a murderer. That's more to do with their morality, personality etc.

Manipulation per se doesn't even necessarily require high intelligence, like someone pointed out emotional manipulation that children do. Emotional manipulation is ez. Actually, in my experience, a lot of dumb people who can't do things otherwise seem to resort to manipulative tricks; intimidation, emotional abuse, lying etc..

The most intelligent people I personally know are the nicest, trustworthy people I've met. I think, since it's not mutually exclusive with empathy, sympathy, morality etc., intelligence may actually help you remain consistent and see solutions that are more in accordance to your values. Also they probably think about what their actions cause in themselves as well as others.

Something about machiavellianism (basically manipulative ppl):
"Due to their skill at interpersonal manipulation, there has often been an assumption that high Machs possess superior intelligence, or ability to understand other people in social situations. However, research has firmly established that Machiavellianism is unrelated to IQ. Furthermore, studies on emotional intelligence have found that high Machiavellianism actually tends to be associated with low emotional intelligence as assessed by both performance and questionnaire measures. Both empathy and emotion recognition have been shown to have negative correlations with Machiavellianism. Additionally, research has shown that Machiavellianism is unrelated to a more advanced theory of mind, that is, the ability to anticipate what others are thinking in social situations. If high Machs actually are skilled at manipulating others this appears to be unrelated to any special cognitive abilities as such.[2]"

So. Immoral shit is immoral shit.

Hitler was a tremendously skilled orator, and a tremendously poor leader.

But what is much more pertinent to this discussion is the historical example he provides: that a great deal of very educated and intelligent people can be swayed into believing something totally horrifying, given the right environment and pressures.

The better question is what exactly does it mean to manipulate someone? Is it to persuade someone to do something they otherwise wouldn't? Where do its boundaries begin and end?

I don't think it's necessarily intelligence that dictates a persons ability to manipulate someone other than them self. It seems that more often than not just having a good eye for identifying social ticks and seeing signals that others normally wouldn't is enough to dictate what someone does without them realizing that you're controlling them. If you want someone to do something for you, and they you have something they want, you tell them that if they do A for you they will get B as a reward. While this isn't actually manipulation, if you do it enough times they will do it automatically because of how the human brain works, it develops scripts that you execute without realizing it. For example, the way you type on a keyboard. Do you type from "home base" or do you type with 1 finger? Maybe you like to move your hands all over the keyboard. Do you stare at the keyboard? Or can you do it without looking? All of these traits are formed by someone who manipulated you into believing that the way you type is the best way to type. It may have been a computer teacher, or your parents, or a sibling. Or maybe you were at the library and you picked it up without noticing. It's not a literal manipulation, but your brain has conformed to thinking that the way you do something is the best way to do something until someone proves you wrong.

Emotional manipulation is a different story, if you can make someone feel the way you want them to through diction and lies then you're just an intelligent dick. Controlling a persons life is not a nice thing to do, stop.

The kind of manipulation that does require intelligence is applied in chess. If you can see what a person is going to do in 15 moves, before THEY know that they are going to make that move, and you can bait them into executing that movement, then you are extremely intelligent. This requires an insane capacity for organizing thoughts and storing those thoughts until you have a use for them.

So no I don't think all forms of manipulation correlates to intelligence. Just the form of manipulation in which you can completely read a person and dictate their future decisions. Plain rewriting of habits requires no intelligence whatsoever, it just requires patience.

Manipulation does not necessarily have to be a bad thing, it is getting someone to do what you want either cleverly or inconspicuously.

By this definition all CEOs and senior officials manipulate people, I think there is a correlation between intelligence and position in a company so i think there is a correlation between intelligence and manipulation

Also by the definition "cleverly or inconspicuously" a "clever" person has a greater chance of manipulating someone and therefore there will be a correlation between intelligence and manipulation

I believe they are correlated because both are evident in every human on different levels of extremities.

Some people are dumb, but that's due to a low intelligence.
Some people are bad at manipulating, doesn't mean they didn't know what they were failing at.

In being co-existent creates a first, simple correlation. To say that they intertwine within one another is a completely different story.
To look at it logically, we have to know what constitutes an intelligent person and we have to address whether or not manipulation is hard, which means that it would take someone considered unintelligent a lot more time and effort to hone.

In saying this, I've come to realize that anyone and everyone can extend their intelligence in any area if they train at it. So someone considered unintelligent at first may become a master of manipulation after years of trial and errors, which would mean he was intelligent after undertaking this?

I'm sensing something close to paradoxical.
I mean, why should people even be dumb?

I guess it all mulls down to motivation, hey?

some people have a natural propensity to improve intelligence in certain spheres quicker, it also probably depends on very early childhood while the brain is still developing, nevertheless, most people can become what other's would consider 'intelligent' if they put in enough time and effort. Whether someone chooses to learn to manipulate is probably the important factor here, since manipulation is the solution to the problem and it might not occur to someone who is not so intelligent that they can get others to do things for them so easily.