Returning to the feature integration theory, it says that during singleton search (red vs. green), reaction times should be constant regardless of the number of items, while reaction time should be a linear function of the number of items when the search involves combining information from multiple feature channels.

You can test this with a junky laptop or even some drawings and a stopwatch. In fact, if you really want, I'll send you a script so you can test it yourself. You can falsify this: just fit lines to the (item count, RT) data and see if the slopes match the predictions. People have, in fact, done this, and have shown that this explanation of visual search isn't quite complete--weird things happen when the target is very rare, for example.

Can you explain exactly what some neuroscience data would add here? Look, I'm not some hardcore dualist. I work in a systems neuroscience group and completely agree that brain-based theories are more interesting than phenomenological ones, which is why I put up with the hours, pay, etc. However, this doesn't make those psychological theories any less valid, nor does it make psychology less of a science.

Anyway, there are lots of other processes that are not directly observable. Gravity, for example, wasn't directly observed until last year. Evolution can't be observed directly either.

Certainly -- it would move the issue from the metaphysical to the physical realm. That might make it science. There's no science of the metaphysical.

> Anyway, there are lots of other processes that are not directly observable.

Yes, but not scientific ones.

> Gravity, for example, wasn't directly observed until last year.

Orbital mechanics both predicts and observes gravity. Each successful spacecraft journey represents another successful prediction of the physical theory of gravity. Dark Energy shows that a physical gravitation theory can be potentially falsified, a property all self-respecting scientific theories must have.

Gravitational time dilation represents an empirical confirmation of Einstein's General Relativity, our present theory about gravity. To be accurate, the atomic clocks on board GPS satellites must take this time dilation into account (as well as that from Special Relativity).

Einstein rings represent another direct observation of gravity. I think you mean that gravitational waves weren't observed until last year. Predicted long ago, finally observed.

> Evolution can't be observed directly either.

There is copious, empirical evidence for evolution. Start with how and why antibiotics lose their effectiveness over time. Then move on to laboratory studies of the evolution of Drosophila Melanogaster (fruit fly), chosen for its short reproduction cycle. Examples abound, all empirical and falsifiable.

These are all examples of experimental confirmation of empirical theories, all potentially falsifiable by observing nature.

I'm still a little hung up on the metaphysical part though.

Suppose we ignore all the baggage around the "mind" and just consider an input/output relationship: a visual stimulus goes in and some response comes out. We can formulate a theory about the transfer function that maps between them, and then test it by applying different stimuli and comparing the observed response with the expected one.

A) Suppose the device is a machine. It initially looks like it responds by beeping when illuminated. However, we falsify this theory by finding different patterns of light and dark, some of which cause the machine to beep and others that don't, falsifying that theory. However, it suggests that some feature of the image may matter, so we test it to see if varying the color of the light matters (it doesn't), or if the relative spacings of light and dark do matter (it does). We try more features and eventually discover that it responds to every single one of the barcodes we try, but nothing else, and hypothesize that it's a barcode scanner.

B) Suppose we're recording from a single neuron in a rat or cat's brain while the animal views a screen. In early experiments, we discover that cells in this brain area--and this neuron specifically--responds to visual stimuli. We adjust the stimuli and note that it only responds to some of the stimuli, so we construct a quantitative model giving the expected distribution of responses as a function of stimulus features. This suggests more tests of the model--perhaps the model has very limited spatial support and thus claims that far apart stimuli have no effect. We present the animal (and thus, the neuron) with stimuli outside the supported region and, to our surprise, the responses change. We revise the model to include some suppressive interactions, and try again....

C) Suppose we're recording the behavioural responses of a human subject. We show the subject pictures of other humans, and ask them to report whether the individual shown is a man or woman. We hypothesise that certain features in the image guide this decision, so we modify the images to enhance or degrade those features and repeat the experiment. Some of these changes have no effect, others increase or decrease the speed and accuracy with which they respond. So, we modify the images more selectively, or only in certain locations, and repeat the experiment, revising our model as we go.

It seems like you would admit A and B as being "scientific", but think that C is flawed. Is this right?

But that's not a theory, it's an observation, and it cannot be falsified, only contradicted. We observe the machine's outputs without any deep understanding of the reasons for the behavior or a grasp of why it's acting as it is. Therefore when we draw a conclusion about a repetitive pattern, and make an assertion about the pattern, we could easily be contradicted by another observer seeing a different pattern and drawing a different conclusion. Those are contradictions, not falsifications.

Say we're an alien, visiting earth, and we see cars moving along a road. By observation we conclude that the cars have to stay in line, no one can force their way through all the other cars. It's a "theory".

Then a fire truck appears and does exactly what we asserted could not happen -- it makes all the other cars move out of the way. But our "theory" is not falsified, it's contradicted. A falsification would require (a) a deep understanding of why cars behave the way they do, and (b) a theoretical falsification based on that deep understanding, not simply a new observation that contradicts an old one.

Another example. For a while there was a mental illness called "Asperger Syndrome". It came into being in meetings of psychologists who talked about it, and who eventually voted it into the DSM.

Everybody liked this new mental illness, it became very popular. Some psychologists even claimed that a lot of famous people had it -- Isaac Newton, Thomas Jefferson, Albert Einstein and Bill Gates, to name just a few. This roster of famous "Aspies" made the mental illness even more popular, especially among young people.

Then things got out of control, and people were actually proactively demanding the diagnosis, for themselves and/or their children. The fact that they could collect Social Security disability payments might have been a factor.

Seeing the clamor about this disease and fearing the consequences of a public backlash, the psychologists held another vote and voted Asperger Syndrome out of the DSM (http://www.nytimes.com/2009/11/03/health/03asperger.html).

So, was Asperger Syndrome falsified? No, not at all. It wasn't falsified because it was never more than an observation -- it never had a theoretical basis. As a result, Asperger Syndrome is neither true nor is it false, and anyone can contradict anyone else while discussing it. By the way, the same thing was true about homosexuality about 30 years ago, with the same controversy and the same outcome -- it was a recognized, listed mental illness, then it wasn't.

This is not science. And it won't be until we understand the brain. Understanding the mind is not only not helping, it's an obstacle, because people have come to think of the mind as a cause of behavior, when it's clearly an effect of the workings of the brain, and science can't be based on effects -- it must be based on causes.