A current article in Science reports on this study about how good people are at predicting what their future selves will be like. Not very good, apparently. Daniel Gilbert, a psychologist at Harvard, with other colleagues conducted several experiments online, in which 19,000 people were asked about such things as personality traits, preferences in music, etc., answering about the present, about themselves 10 years earlier, and about what they expected 10 years hence. More precisely, this not being a longitudinal study, people of any age X predicted less difference with their X+10 selves than people of age X+10 recollected of themselves at age X. The effect did not go away with increasing age: 58-year-olds still expected less change in the next 10 years than 68-year-olds reported in the last ten.
Gilbert and colleagues call this effect "the end of history illusion," because it suggests that people believe, consciously or not, that the present marks the point at which they've finally stopped changing.
"What these data suggest, and what scads of other data from our lab and others suggest, is that people really aren't very good at knowing who they're going to be and hence what they're going to want a decade from now," Gilbert says.
Someone suggests an alternative explanation:
Another possibility is that people "might well anticipate substantial change, yet not know how they would change, and thus, just predict the status quo"
An actionable moral:
"The single best way to make predictions about what you're going to want in the future isn't to imagine yourself in the future, … it's to look at other people who are in the very future you're imagining," [Gilbert] says.
Well, yes, in that we'd have to explain how my present self ended up with memories of what are now my friend/peer's experiences, among other things. Any explanation of that is bound to be pretty damned strange.
That said, I do agree with the general principle that the differences between me at various different times are potentially radical enough that definitions of "my identity" based on similarities will pick out a different set of person-moments than those based on continuity. Personally, I'm content using a pretty broad similarity-based definition that includes lots of discontinuous person-moments, but others' mileage varies.
I don't think that your declarative/explicit memory is all that important to your identity, the influence those experiences had on your cognitive algorithms, certainly, but the explicit memories themselves? Of course any path that would take a 10-years-younger peer of yours to your current identity would be strange, even somewhat stranger than the semi-random walk you yourself took. But it is conceivable, i.e. your past and long gone personae were part of your path through time and space to your current self, but they aren't strictly necessary to get to where you are now. Mostly, they're just gone.