Neuroscience has a problem. It may appear to be a mere philosophical problem but has practical implications for the broader philosophy of science and the scientific method.

One of the big projects is the correlation between states of the brain and states of mind. It isn't the only project but it is an important one. On one side of the equation we have a battery of biological, chemical and physical data regarding neurological activity at the level of the neuron and brain plus possibly other physiological processes. This domain poses few problems in producing data that is acceptable as employing a scientific method. On the other side of this correlation we have what can variously be called states of mind, states of consciousness, cognitive experiences or just plain experiences. And more often than not, the only access the neuroscientist has to such experiences is to ask the person. Introspection is back as a scientific method!

"In a variety of ways, the advent of sophisticated imaging of brain activity has created a new reliance on introspection — it is difficult if not impossible to relate what is going on cognitively to various brain activities without self-reports from subjects about what is going on in them. " say Andrew Brook and Pete Mandik. "It is perhaps a bit ironic that neuroscience, the most scientific of approaches to human nature to date, has been forced to fall back onto a technique rejected as unscientific over 100 years ago!"

Introspection was rejected as being unscientific for a variety of reasons that include: the information is difficult to replicate; people are prone to confabulate or present a rationalised picture; and that subjects are often not aware of their own internal experiences or are unable to explain them in a systematic way. There haven't, as yet, been many solid philosophical solutions put forward. But does this really go against the hypothetico-deductive model of the scientific method? Data from human behaviour comes with a greater variability than would be acceptable in the physical sciences but that is a matter of degree and has not put a stop to the social sciences. Rather than answering this now, I'd like to leave it open for discussion.

Neuroscientists, and especially those working in areas such as the neural correlates of consciousness are pressing ahead with their research so that at some practical level this appeal to introspection is not a serious problem. The sheer necessity of using introspective reports is leading to a reevaluation of its role in science. But some neuroscientists and philosophers of neuroscience have picked up on this twist in the history of science.