So what is the practical definition of personality?
Is personality the built-in formula for determining what a person will do in a given situation?

Pinker shows us that personality is determined partly by genetics and partly by the random growth patterns of our brain tissue.

After reading this I considered a thought expiriment:

What if identical twins were somehow engineered to have the exact same growth patterns of their brain tissue? Probably this is impossible, but let's just assume it.

And what if somehow you could arrange for them to have the exact same experiences as they grew older? This is perhaps even more impossible, (if that makes sense,) but imagine we could do it. And I mean, exactly the same experiences...the gleam in Mommy's eyes, the exact physical perturbations (farts, itches, etc,)
the same summer breezes and spooky creaking noises at night, and all that. Perhaps it is concievable if we imagine some kind of futuristic virtual reality machine.

So if we could do this, if we could create identical people and raise them in the exact same way, would they unerringly live out identical lives? Would they each make the same decision at every possible moment? Brush their teeth the same exact way? Have the same daydreams? Marry the same (virtual) person? Breathe the very same last words on their deathbed?

It seems to me that this must be so. And this thought seems to bring me face to face with my own "machineness" in a new, more undeniable way.

I suppose there may be other forces at work that would make the destinies of the two people vary. Perhaps the random behavior of subatomic particles would butterfly up, and lead to different
toothbrushing styles, that could lead to different success at dating...

But then we could modify the thought expiriment to include control of these forces...Unless we invoke a force that is in principle uncontrollable.

Oh, I'm rambling now. Anyway, that is how I've been thinking since reading the Blank Slate.

OK, I'm replying to my own message here to apologize for not hitting spell check before posting. It was my first post, and I was all excited. Hopefully my errors don't irk you too much!

Hi, Mark!

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So if we could do this, if we could create identical people and raise them in the exact same way, would they unerringly live out identical lives? Would they each make the same decision at every possible moment?

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How could they make the same decisions, when they do not occupy the same space?

I agree, it's not possible to give them the same exact experiences. I'm afraid they can't help but individuate!

You might enjoy some of the sf works on cloning (it was a popular topic in the late 70s.) Kate Wilhelm had a number of books playing with these ideas; as I recall, there were a few anthologies on cloning, too. (Clones as identical personalities; clones who were forced by circumstance to diverge from their fellows, etc.)

I'm a big fan of science fiction and philosophy that deals with identity. I haven't read Kate Wilhelm though. I'll check it out.

So are you saying the subjects of my above thought expiriment will individuate because they are in different places? Or just because they can't really have the same expiriences? I'm really very eager to understand all opinions on this.

If personality is viewed as a formula for decision making, then it follows that the same input will yield the same output, no?

Mark

Excellent post...one I wish I had caught earlier. It would be interesting to see how Pinker answers your questions, and I might be tempted to get in touch with him if this conversation generates enough interest.

Your identical twins scenario is intriguing, and I too wonder what the outcome of such an experiment would be. I'll admit that I hope it is completely impossible to learn what all the factors are that go into creating our personalities and then to control those factors. If it can be done...someone will do it. How scary.

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I suppose there may be other forces at work that would make the destinies of the two people vary. Perhaps the random behavior of subatomic particles would butterfly up, and lead to different toothbrushing styles, that could lead to different success at dating...

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Let us hope there really are random components to our personalities, such as at the subatomic level, or we'll soon have a whole new type of cloning. Can you imagine complete duplicates of people? Nah, I think we'll never get that far in cloning. It seems improbable that we could ever identify every single factor and then completely control them perfectly so that two distinctly separate organisms experience the exact same experiences.

But what an intriguing thought...

Chris

"The man who does not read good books has no advantage over the man who cannot read them"

I'm reading what I just said and thinking about how Tiarella responded and wondering now if my post made any sense.

As Tiarella stated no two people can have the exact same experiences as they occupy different physical places in space. Even if they were attached at the hip they're still experiencing drastically different perspectives. So this is definitely one of those hypothetical situations that is merely fun to contemplate.

I guess the real question is as follows. Are we a product of a finite set of factors or are there random elements involved in the formation of our personalities? I'm not asking if we'll ever identify all of the factors, because I see this as practically impossible. But is the set finite? As Mark put it...are we really just machines behaving as programmed? If two organisms were exact duplicates in every respect, would there be an element of randomness in each personality?

Chris

"The man who does not read good books has no advantage over the man who cannot read them"

I remember a thought experiment I came up with some years ago.

Imagine that there was a solar system exactly like ours and that every single atom was in the same place and had the same velocity and direction relative to every other as they do in ours. Lets further imagine that all the stars and galaxies looked exactly the same from that solar system as they do from ours.

It seemed obvious to me then that the Peter Fisher on that Earth would behave exactly like I have thoughout my life, make all the same mistakes, have shared all the same successes and failures and be sitting here writing this exact post at exactly the same time and on the same date as I am.

I have to add, that I came up with this before I found out about Heisenberg's Uncertainty Principle.

But I'm still not convinced that my thought experiment doesn't still hold because although we can't ever know all there is to know about the laws of nature it does not follow that they don't all hold to be true even if we can't know that to be the case.

Edited by: PeterDF at: 4/9/04 6:26 am

Interesting. I imagine it differently.

If there were an exact duplicate of me in an exact duplicate of this world, I believe that my duplicate would sometimes make different choices than I did - because there's an element of chance involved in all our lives. And I simply can't see "chance" being exactly duplicated - can you? The flipped coin that comes up "heads" here may come up "tails" there. So it's extremely unlikely that there is an exact duplicate me in an exact duplicate world in an exact duplicate universe, because the element of chance would've resulted in a divergence from this universe/world/me long before I ever came into existance.

Tiarella
No! No! No!
The coin would always fall the same way because it would encounter the same energy input and experience the same air resistance; it would have exactly the same mass and fall exactly the same distance in each situation. Chance could only play a part if there were a random element introduced into the system otherwise it would be entirely determined (even if not determinable). If we ignore (what seem to be the random effects of) quantum mechanics at the sub atomic level and outside effects (like a passing neutrino from a distant star disturbing things) The two systems would play out exactly the same futures.

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And I simply can't see "chance" being exactly duplicated - can you?

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No, I agree; it could never happen in practice because both star systems would have to have identical outside influences (the stars, galaxies and all visible, non-visible and radio astronomical phenomena would have to be identical for it to work). I agree that no matter how big the universe this is way way outside the bounds of possibility but in our thought experiment I still say that the history and futures of the two star systems would be the same.

Edited by: PeterDF at: 4/13/04 11:00 am

Peter

*grins*

Ahh, but I wasn't thinking about a coin flip; I was thinking of times when I was making a decision and almost made a different one. The experience leaves me with a visceral feeling that were it possible to replay the scene again and again, then I'd choose evenly between several alternative courses of action in the replays. Your theory contradicts my gut reaction, which, of course, does not invalidate your theory.