[angryprofessor]

Ideas could cause aggression, certainly. Lots of things can.

However, we DO know chemicals can in humans. Pot and ecs reduce aggression, while meth increase it. I don't know if particular mechanisms are understood, I'm not a biochemist. But empirical observations do show that chemicals (in some way) affect aggression (and other emotions).

As for ideas, we don't know the mechanism there either. In fact, we understand the mechanisms of thought less than those of emotion. I can predictably make you and other humans I don't know happy or sad with chemicals; I can't do the same with ideas.

[curi]

Empirical observations show that chemicals have some correlation with emotions, which does not imply that either causes the other.

Being able to make people happy with chemicals is consistent with emotions being purely ideas. It just takes a subconscious idea to interpret certain sensations, caused by the chemical, in a positive way. And for this idea to be shared by most people in our culture.

[angryprofessor]

>Empirical observations show that chemicals have some correlation with emotions, which does not imply that either causes the other.

Timing and randomization shows that chemicals are the cause. Double blind experiments must have been done at some point, which would show the effect is causative.

As for drug effects being cultural, I disagree. Amphetamines also cause aggression in rats, for instance:

http://www.springerlink.com/content/p2745782608v6558/

[curi]

My reasoning for why chemicals do not cause high-level human personality traits depends on intelligence, so experiments on non-intelligent rats do not contradict my position.

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Double blind experiments (with controls, randomization, etc) do not show causation, they show correlation. You need to have an explanation of what the cause is, or that kind of study doesn't get you anywhere. Because without an explanation, you don't even know what you should be looking for, or have any idea why that correlation exists.

BTW, if you know of a reputable, scientifically-oriented source which believes that double blind experiments demonstrate causation in the absence of an explanation, not just demonstrate correlation, I'd like to see it.

[angryprofessor]

So you are proposing that chemicals cause aggresion in rats, and aggression in humans, but for a different reason? Seems unlikely to me.

Double blind experiments do show causation (ignoring metaphysical discussions).

There are 3 possibilities: Chemical -> Behavior, Behavior -> Chemical, or ??? -> (Chemical and behavior).

A randomized trial eliminates the latter two possibilities (since chemical is correlated only to a coin flip). Double blind eliminates experimenter bias.

[curi]

So suppose we are studying sad people, and we randomly give some of them a chemical, in a controlled and double blind way. And those people become happy, and the others don't.

Then, it could be that the chemical somehow causes happiness. Or it could be that the chemical causes memories of one's children, and everyone in the study has happy memories of their children.

So, the causation is still in doubt. Many explanations are consistent with the observed data.

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Yes I am proposing that chemicals correlate with "aggression" in humans and rats for different reasons. But I don't accept that the thing called "aggression" is the same thing in humans, and in rats. To help illustrate why not, consider aggressive behavior by video game characters. Same word, but not the same phenomenon -- in that case, no emotion is present, and the cause is some C code.