You will be given a definition of a task first, then some input of the task.
This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: Some research suggests that "[f]or some [people] the focus of sexual interest will shift at various points through the life span..." "There... [was, as of 1995,] essentially no research on the longitudinal stability of sexual orientation over the adult life span... It [was]... still an unanswered question whether... [the] measure [of 'the complex components of sexual orientation as differentiated from other aspects of sexual identity at one point in time'] will predict future behavior or orientation. Certainly, it is... not a good predictor of past behavior and self-identity, given the developmental process common to most gay men and lesbians (i.e., denial of homosexual interests and heterosexual experimentation prior to the coming-out process)." Some studies report that "[a number of] lesbian women, and some heterosexual women as well, perceive choice as an important element in their sexual orientations." Question: Until 1995 what had no studies done concerning sexual orientation?
Output:
longitudinal stability of sexual orientation over the adult life span.