There was a time when you could go to a documentary knowing that whether good or bad, “objective” or argumentative, it was seriously trying to convey some aspect of reality. If something was a mockumentary, it was understood and billed as such. But those days are apparently past. We’ve just gone through the experience of “I’m Still Here,” the brilliant piece of performance art by Joaquin Phoenix and Casey Affleck that fooled a great many people about what it was, before the cat was let out of the bag. And now there’s “Catfish,” which also poses the question: is it real, or is it not?

In the simplest terms, and without revealing its twists, the picture purports to be the record of an Internet-based connection between New York photographer Nev Schulman and an eight-year old Michigan girl named Abby Pierce, an artistic prodigy who makes contact with him by painting a version of one of his published stills. Before long, Nev has developed an on-line friendship with Abby’s sweet mother Angela and with her elder daughter Megan, in the latter case quickly moving into long-distance romance. Happily Nev’s older brother Ariel and his partner Henry Joost are aspiring filmmakers, and have been documenting the rather reluctant Nev from the first. Now they can keep a record of the paintings Abby sends her pal via snail mail, the e-mail messages and phone calls, and the entries all the parties post regularly on Facebook.

The story takes a turn when Nev and the guys filming him begin to suspect that the Pierce family isn’t precisely telling them the truth. So they go to Michigan unannounced to investigate. At this point one might expect the narrative to take a scary turn, and the filmmakers don’t discourage the idea, especially in a scene where the boys make a late-night stop at Megan’s isolated horse ranch. You think that a Great Lake version of Leatherface is poised to jump out of the shadows with a giant-sized chainsaw.

This sort of shift isn’t entirely surprising, given that one of the film’s executive producers is Andrew Jarecki, whose exceptional documentary “Capturing the Friedmans” became a similarly disturbing study of truth and falsehood halfway through. But one could never doubt the veracity of what one was seeing in that picture, even if you thought the presentation manipulated the evidence. In this case the situation is much murkier.

For one thing, the material very easily falls into the messages it’s designed to deliver, and it’s curious that they go in two directions simultaneously. On the one hand, the picture acts as a cautionary tale warning about the dangers of duplicity in online communication. But in the end it also tries to show how such communication can help relieve the personal burdens that encourage that sort of deception and break down the walls of isolation that make it possible. Frankly, the very perfection of the picture’s “accidental” argument makes it suspect as a true documentary.

Then there’s the presentation. There are numerous scenes that seem staged, particularly in terms of camera movement and perspective. And quite honestly, with one major exception the cast appear, to this reviewer at least, to be acting. That’s certainly the case with Nev, a likable fellow to be sure, but one who’s trying too hard. And when Angela’s husband delivers a supposedly impromptu speech that turns out to be the device that gives the movie its title, it comes across as not just entirely too convenient but scripted.

I’m ready to believe that “Catfish” might be a recreation of an actual experience, though one carefully structured and arranged to get the makers’ ideas across. I’m willing to accept that within that context a lot of the scenes were improvised. But there’s too much about it that’s—excuse the pun—fishy for me to be persuaded that it’s a documentary in the true sense.

I’ve recently been watching two DVD sets—one is the 1982 PBS series “Middletown,” about some residents of Muncie, Indiana, and the other is a collection of the features by the late Canadian filmmaker Allan King. If you want to see a real documentary, dip into either of these. The contrast with “Catfish” will astonish you.

That isn’t to say that this film doesn’t raise some provocative questions in an intriguing way—it does. But in the end its answers seem just too pat, and frankly unrealistic.