A brilliant series of papers have been produced recently on the topic of U.S. Supreme Court justices' ideological change over time. Authors on these papers include Andrew Martin, Kevin Quinn, Lee Epstein, and Jeff Segal, although the author groupings change by paper. Most of the papers can be found on Quinn's website. To put this very briefly, the authors suggest that - contrary to what prior research claims - Justices' ideological preferences, or ideal points, are not time-invariant, but rather change over time (or at least most of them do). The authors show that justices' revealed prefrences (i.e. voting) change over time, independent of factors that aren't justice-specific that might affect voting (e.g. changes in the type of cases the Court hears).
In "Assessing Preference Change on the U.S. Supreme Court," Martin and Quinn make a very strong case that justices' ideal points, as revealed in their voting, are not time-invariant. This has important implications for the way we study the Court. However, in the conclusion they posit a very important question that they leave to future research: What explains preference change? We basically, need a measure (exogenous to justice votes) to provide a representation of the justices' sincere ideological beliefs over time. We have time-invariant measures, such as party identification or social background, but coming up with time-varying measures presents a bit of a puzzle. The authors suggest that we can look toward factors affecting preferences offered by social psychology, stragic considerations, and the macro-political context.
I am working with two UGA graduate students, Brian Levey and Justin Moeller, on the early stages of a project that seeks to answer just this type of question. While we have certainly not "cracked the code," on this puzzle, but we are working toward a strategy for explaining change in ideology over a person's life. We hope to develop a method of explaining revealed ideological preferences that can be applied to policy makers generally. Arguments have been made that, for instance, members of congress and presidents change their attitudes over time. Explaining such change is easier said than done, to be sure.
With this goal in mind, I'd like to take a step back and address the basic question - assuming that people do change their sincere ideological preferences over time, what causes such change? Do you know someone whose ideological preferences have changed over time? If so, what do you suspect caused this change? Is it possible that we could apply some of the methods used by Neal Tate (1981) in his seminal article using social background factors (e.g. father's occupation, justice's education, etc.) to explain justices' changing ideological preferences, as revealed in voting?
Of course, there is a rich behavioral literature in political science and other disciplines on how citizens' attitudes are formed, and some literature to suggest why they change. It is possible that justices' attitudes are changed over time by the collective preferences of their social networks. Thus, a change in ones social network might lead to a change in their attitudes or ideological preferences. Other socializing events and phenomena may also prompt change in ideology.
If we consider Supreme Court justices as an example, such events or phenomena (occuring after their confirmation) might be: where they live (change in residence or significant time spent in new surroundings), changes in personal status (marriage, divorce, children, grandchildren, death of a family member), or role on the bench (more senior, elevation to CJ, etc.), among others. There could also be interactive concerns whereby changes in personal status affect justices differently based upon certain conditioning factors.
Of course, this is all just my early musings on this question, but I would be interested in hearing what other people have to say on this topic.