Part of the problem here is that even if testosterone had absolutely no effect on aggression at all, we would still see people taking testosterone injections acting more aggressive. Why? Because the common belief is that testosterone will make you more aggressive. Give them saline and tell them it's testosterone and they'll start bumping people in the street as well.

To test whether there is an actual effect going on here, they'd need to look at what how two different groups of FtM transsexuals respond when one is placed on a placebo, and one given testosterone. The article linked to by Gwern discusses this effect of perception on behavior:

Folk wisdom holds that testosterone causes antisocial, egoistic, or even aggressive behaviors in humans. However, the correlational studies discussed above already suggest that this simple folk view probably requires revision [34,56]. A recent placebo-controlled testosterone administration study found support for the idea that the testosterone–aggression link might be based upon ‘folk’ views: individuals given placebo who believed they had been given testosterone showed less fair bargaining offers compared with those who believed that they had received placebo, thus confirming people’s stereotypes about the behavioral effects of testosterone. More importantly, however, when statistically controlling for this belief of treatment assignment, one acute dose of testosterone in women increased the fairness of proposers’ bargaining offers in an ultimatum game [13] (Figure 3).

Then "human behaviour is predictable" doesn't apply to life in general.

Yes it does since we know that human behavior is predictable. Scientists don't need to add "in controlled environments" because that's necessarily the case. Nothing, absolutely nothing, is predictable in uncontrolled environments. So if you're saying that human behavior is unpredictable because it can't be predicted in uncontrolled environments, then you've simply defined human behavior (and everything) as being unpredictable. How did you describe this kind of argument? "And 11 fingered people have 11 fingers"?

Predictability in controlled experiments isn't taken by physicists to prove a sweeping statement like "the universe is predictable". Some physical system are well known to be unpredictable.

Your analogy is a misrepresentation. Behavioral scientists saying human behavior is predictable is akin to physicists saying that the movement of a falling object is predictable. The fact that physicists can only predict the motion of falling bodies when they know the mass of the object, the force of gravity, etc, does not mean that they have to say, "Falling bodies are predictable in controlled environments, but they are unpredictable in the real world".

Or some other reason.

There cannot be any other reason.

Which is to say that some real situation have straightforward rules and rewards, allowing predictability.

So it's just a coincidence that every "free range" behavior which has been tested happens to be predictable?

Oh we know that, They are.

You think the movement of billiard balls are unpredictable because of "quantum mechanics"?... You do understand that indeterminism and probabilism do not preclude predictability, right?

No, it doesn't necessarily mean that.

There is no other option.

That, again, is getting what you are looking for.

No. Knowing the variables in an environment does not mean you get what you're looking for. There is an almost infinite number of ways in which the variables could be combined to reach different conclusions and predictions. If we come up with a law that uses specific parameters that give us an accurate prediction, then that means the phenomenon we're observing is predictable.

I don't understand why you think controlled environments (i.e. environments where the values of parameters are known) automatically produces some behavior or outcome. That's nonsensical.

No physicist would say physics is successful in predicting without specifying a system. What does "human behaviour is predictable" mean? We already knew you could predict behaviour in some situations, so that isnt a discovery. And we don't know that it is predictable by and large, because it isn't.

"Human behavior is predictable" means that human behavior can be predicted. Informally we might have known that behavior is predictable in some situations, but that's no better than saying "We already knew that the effects of gravity are predictable because when we drop stuff it always goes down". The point is that as long as we have information on the values of parameters, then human behavior is predictable. Pointing out situations where parameters are unknown does not mean human behavior is unpredictable.

It ipredicts where it predicts and doesn't where it doesn't. If you are going to ask whether something is predictable without adding any riders about to what extent,and under what circumstances , the quesiton would reasonably be taken to apply in the raw, to "free range" behaviour. I would not be taken to mean "under controlled circumsrtances"

All science only makes predictions within controlled circumstances. If you booby-trapped a billiards table, so there were unknown valleys and crests on the surface of the table, you wouldn't disprove physics because suddenly a physicist can't predict the motion of a billiard ball.

In uncontrolled circumstances our predictions become less accurate because there are literally millions of unknown variables. But, of course, since humans are so predictable, we can make decent enough predictions - for example, we can predict how much time, and to whom, a person will dedicate talking to at a dinner table. We can also predict, with reasonable certainty, when a basketball player will take a 2-point shot over a 3-point shot, or what play a football coach will play at any given time. So whilst our predictions are imperfect, they are still accurate enough.

And this isn't even taking into account applied settings, like cognitive behavioral therapy, and applied behavior analysis - both of which are accurate enough in "free range" settings in order to treat and cure a number of conditions like anxiety, depression, autism, etc.

Of course controlled behaviour is predictable, that is what "controlled" means. And 11 fingered people have 11 fingers.

If I had said "controlled behavior" then you'd have a point. But I didn't, so your comment here is redundant.

You don't know that. To know it. you would have to exclude basic physical indeterminism, and the jury is still out on that.

Physical indeterminism is irrelevant since we're talking about the macro world. If we have to wonder whether human behavior is unpredictable due to some quantum mechanic weirdness, then we have to equally wonder whether billiard balls are unpredictable due to some quantum mechanic weirdness as well. The point is that we know human behavior is perfectly predictable in controlled experimental conditions, and less predictable in situations where some variables are unknown - this necessarily means that the myth of people being unpredictable is a result of ignorance of variables.

You get what you are looking for. Ask them to write a story or paint a picture, you do not know what you are going to get..

Once we can control the variables, of course we do. We can make them write a story or paint a picture of whatever we like.

No it doesn't. It predicts the behaviour of controlled individuals. You have no idea what the people around you in the office or street are going to do next.

Not "controlled individuals", you mean "controlled environments". And yes, of course people in the street are less predictable because we don't have access to relevant variables.

Out of interest, I take it you apply your criticisms of behavioral science to all other sciences? Physics is not successful at predicting the movement of objects because it cannot give me the exact time that a rock balanced on top of some mountain in the Northern Hemisphere will topple over.

Your example is a bit absurd - why would the prediction of human behavior necessarily entail the prediction of behavior in a completely uncontrolled environment, with near-to-zero information on any relevant variables?

Your question is comparable to asking: If physics was so good at predicting the movement of physical bodies, then why can't it predict earthquakes? If it can't predict when an earthquake will occur, then it is not successful at predicting the movement of physical bodies.

The point is that we know that humans are incredibly predictable. The reason why humans appear to be unpredictable is simply a product of the vast number of unknown variables acting upon us at any given time. When we remove these variables, and place a person in a controlled experimental environment, the result is highly predictable human behavior. As I pointed out above, we are very good at predicting how people will respond in choice situations, and self-control situations, etc.

The great thing about behaviorism is that not only does it point out that human behavior has causes, but it identifies these causes and quantifies them in simple laws that accurately predict the behavior of individuals. In other words, there's a reason why behavioral science (underpinned by behaviorism) is considered a natural science.

Why do you say that behaviorism has not been successful at predicting human behavior? Its most popular models of choice behavior consistently account for around 95% of the variance in experimental settings (e.g. the matching law, or the contingency discriminability model). Behaviorist accounts have disproved naive conceptualisations of the "rational agent", and have developed models of self control which not only accurately predict at what point an individual will choose the smaller-sooner reward over the larger-delayed reward, but they also predicted a previously unnoticed behavioral phenomenon (i.e. preference reversal).

I'm aware of no other area of psychology which has been as successful at predicting human (and animal) behavior as behaviorist theories. The success of behaviorist accounts to not only predict, but also to control, human behavior is one of the features why behaviorism is considered one of the most useful approaches to psychology.