Baroness Susan Greenfield has an idea. It's a scary idea that could have far-reaching consequences for our society. Greenfield has used newspapers, magazines and television channels to promote her idea. This has caused alarm, and other academics have demanded that she properly publish her idea with supporting evidence in a research journal.

There's one big problem though; nobody seems very sure what Baroness Greenfield's idea actually is.

Mark Henderson, a former science editor at The Times, talked to the scientist about her idea on Channel 4 News a couple of nights ago.

I wouldn't say that it was bad for the brains because that implies a straightforward health issue, it's more that I think our brains are adapted to do many things, and if one obsessively does one thing then by definition you're excluding other things like living in three dimensions, having three dimensional relationships...

Greenfield was talking about social media (specifically Twitter), which she claimed to have never used. Her idea seemed to be that if you use social media obsessively it might reduce your quality of life; but that seems quite trivial and banal - doing almost anything obsessively might reduce your quality of life.

This wasn't the first time Baroness Greenfield had presented her idea to the public though, and on previous occasions she stated it very differently.

In 2009, Greenfield told us that "a world without long-term relationships, where people are unable to understand the consequences of their actions or empathise with one another [...] is a plausible future", described our growing "dependence on websites such as Facebook, Twitter and Second Life", and declared that, "One effect, the fragmentation of our culture, is already occurring."

In 2010, Greenfield wrote that "the human brain is under threat from the modern world." She told us to "wake up to the damage that the gadget-filled, pharmaceutically-enhanced 21st century is doing to our brains," and declared that, "Today's technology is already producing a marked shift in the way we think and behave, particularly among the young."

In 2011, Susan Greenfield linked "an increase in people with autistic spectrum disorders" and "happy-slapping" with "the rise in the appeal of Twitter," and told her interviewer - science writer Frank Swain - that, "we should be planning a 3D environment for our children [to enjoy] instead of putting them in front of a 2D one."

In the same interview she said "I didn't say, and I've been misquoted universally, that [technology] rots the brain and it's bad, I've never given value judgements, ever," which was odd given the other things that Greenfield had said previously, such as when she wrote about "the damage that the gadget-filled, pharmaceutically-enhanced 21st century is doing to our brains."

In order for Baroness Greenfield (or other scientists) to research her idea, she needs to be able to state it in the form of a clear, testable hypothesis. If we piece together all of the above, what is it?

Baroness Susan Greenfield's hypothesis seems to be that an unknown level of use of some subset of technology could harm our brains, and may already be damaging large swathes of society that may or may not be limited to children, although possibly only with obsessive use.

The technology in question is specifically but not limited to social media, and may include 2D media such as 3D computer games and televisions though not apparently books, whose dimensionality is unclear in this model although presumably the dimensionality of ebooks is one less than whatever that figure is.

These technologies disrupt the ability of children to understand empathy, or possibly causality, or possibly make them forget how to form three-dimensional relationships in the real world, which are like two-dimensional relationships with one additional vector, though not apparently to be confused with a three-way.

The impacts may or may not be seen in anecdotal evidence on various phenomena including but not limited to and in no particular order the incidence of happy-slapping, a general decline in empathy and social skills in the population, and a possible correlation between the rise of social media and an increase in autism diagnoses since the 1980s.

In short - as far as I can understand it - Greenfield's hypothesis is that an unquantified level of exposure to an unspecified subset of modern technologies may be affecting an indeterminate number of people's brains in an undefined way, with a number of results.

If you find all of this confusing then you're not alone, because if you put all the above together there's only one thing that you can say about Baroness Greenfield's idea: that nobody seems to be able to state very clearly what it is.

That's a problem, because without a well-defined hypothesis it's hard to do any meaningful research - especially if, like Greenfield (a professor of synaptic pharmacology), the subject isn't really in your field.

Mark Henderson asked Baroness Greenfield what research she had done on the issue on Channel 4 News the other night. "So far as I'm aware, and please do correct me if I'm wrong," Mark offered, "you haven't published anything in the academic literature on this, which is - as you know as a scientist - the proper forum for raising such concerns; and I'm very interested to know why you haven't done that and whether you intend to?"

Greenfield replied, "If the argument is, as a neuroscientist, have I published on the impact of the environment on the brain" - it wasn't - "then yes I have."

"But on Twitter specifically?" Mark badgered.

"Well Twitter is part of the environment," Greenfield responded, even though she had spent the previous five minutes arguing that Twitter was a special, two-dimensional environment, unlike normal environments. "The issue is more how the environment is impacting... the cyber-culture is impacting on the brain, and that's been the basis of my concerns, if you're asking me to comment on someone else's comments I'm happy to do that and it's a rather ad hominem argument that Mark's trying to dredge up now."

In January 2010, Dr Ben Goldacre made this plea to Greenfield:

If you believe that computers - which are widespread - pose a serious environmental hazard to children, then you have a responsibility to your peers and most importantly the public to present your theory clearly and formally in an academic journal, so your scientific peers can assess it.

Two years have passed without reply. Meanwhile, Baroness Susan Greenfield continues to use the media to promote her idea. Or her ideas. Maybe there's more than one idea. Maybe one day we'll know what it is, or what they are. Or maybe we never will.

I wonder, does she?

Twitter: @mjrobbins