It's tempting to try to find a point in time when an old zeitgeist fled and a new one took over. Anyone who does this in print must recognize that they're generalizing. After all, even in periods of real tumult, the zeitgeist is really just a constellation of attention-grabbing characteristics that mostly move independently of one each other. Art history example: the Renaissance is widely considered to have become the Mannerist period by the time Michelangelo began work on the the Last Judgment in 1537. But can we find a transitional work and point at emerging themes and say, here, this is the inflection point? Doing this with culture is not quite as easy as in biology, where there must be a clear linear descent.
Defining an age and trying to find its joints is necessarily a sloppy business, but this doesn't stop us. John McWhorter is a linguist, formerly of UC Berkeley and now with the Manhattan Institute, who wrote Doing Our Own Thing: The Degradation of Language and Music and Why We Should, Like, Care. McWhorter is a lover of the English language and the pages of this book mostly take the form of an elegy for a formal style of rhetoric (or really, the existence of rhetoric as such) that has passed into history in the United States, evidenced by the lesser demands placed on modern music and public speech. Mass media provide sensible landmarks of public taste for these kinds of discussions because they're a shared experience. McWhorter expounds on why the shift might have occurred and repeatedly comes back to 1965 as the inflection point, going so far as to find a "transition species", a so-called cultural archaeopteryx, in a live performance by Sammy Davis Jr. that had one foot in the old, formal style and one in the new, structureless, self-indulgent informality. McWhorter argues that a host of values and attitudes shifted along with this sharply punctuated 1965 transition.
Thoughtful people interested in the cultural changes of their country (and where they fit into it) can't help but find these speculations engaging. Probably the most famous treatment of the shifting of attitudes is Strauss and Howe's Generations. They attempt to explain history in cyclic terms with 4 recurring generational types, each determined by the nurturing patterns of the previous generation.
Without addressing Strauss and Howe's generational types, I've often speculated that a more recent and perhaps less profound cultural transition took place around my own coming of age, and there's a link to McWhorter's 1965. The 1980s in the U.S. - when I passed from kindergarten to tenth grade - in retrospect seem an oddly conservative island, a repeat of the 50s sandwiched between the era of disco, drugs and Vietnam on one side and grunge and the early internet on the other. Why? The kids of the post-1965, post-formal generation weren't yet out in the world on their own, independently interacting with the world, spreading those post-formal values. If you got married in 1963, had your first kid in 1965, she would have started college in 1983, carrying forward her parents' pre-1965-transition values. On the other hand, if you met at Woodstock and had your first kid two years later, she would start college in 1989.
What Happened in 1990?
My inspiration to collapse my thoughts into this blog post was a post on Andrew Sullivan's blogs, showing a sharp positive change in public perception of gay people in 1990. On this specific topic, try watching a few "socially conscious" 1980s movies that wear their values on their sleeve; they're recent enough that you expect their values to be the same as yours, but they're not. (The same argument can be made for why I am annoyed by the characters' values as they relate to gender roles in Bronte and Austen novels in a way that I am not by, say, Chaucer.) But the pro-gay attitude shift is just a canary in the coal-mine. In the early 90s, suddenly kids were growing their hair long on masse again and wearing lots of black and talking about conformity, there was loud angry music and grunge everywhere, and pot use skyrocketed. Coincidence? Or the coordinated coming of age of the first post-formal generations' kids?
There's no one archaeopteryx for the 1990 shift, which in any event wasn't quite as dramatic as 1965, but here are a few: 1989 had Batman, which celebrated "dark" (new to mainstream American film audiences); 1990's Dances with Wolves had the first naturalistic and positive treatment of Native Americans (imagine that in 1985!) and in 1991, Terminator 2 shows us the badly-behaved punk kid (the young John Connor) whose criminal sensibilities end up serving him well. Imagine a pubescent criminal as protagonist and hero on the mainstream big screen even in 1988. Musically, in rock, late 80s thrash (underground, no airtime and little MTV exposure) gave way fully to grunge by 1992 (on MTV you couldn't get away from it).
Is It a 25-Year Cycle?
If the pattern is real, then we're due in 2015 for another shift. But I have my doubts that it will remain cohesive. The use of mass media as milestones is becoming potentially problematic, because the way we consume media (and create it) has changed so much. On the other hand, it's the spread of values that shapes these shifts, and thanks to technology that process has never moved so quickly. Unfortunately I can't make a prediction because I don't have a sense of which values will carry over from the early 90s and dominate the new zeitgeist, just as it would have been difficult in 1989 to make the same kind of call. Check back in 2017; by then such a shift should be obvious.
[Added later: Razib Khan separately notes an inflection point also in 1990 for another sexual more, black-white dating.]