It’s the 21st century, and technology and the economy have changed everything. As a result, we have discarded a lot of old notions — and it’s time to dump several others.

For example, let’s abolish the idea that an actor needs to be seen on camera in order to give a “real” performance. Scarlett Johansson creates a full character in “Her,” so she should be seriously considered for supporting actress.

The Rome Film Festival this week gave her the best actress prize. Fests are pretty unreliable as Oscar predictors, so it’s hardly an omen. But it IS a heads-up that some people are able to think outside the usual parameters. The Academy and SAG Awards have affirmed that she’s eligible; with Globe ballots going out Nov. 27, the HFPA hasn’t determined yet, but the org has often taken pride in pushing the envelope in its voting, so fingers are crossed.

For me, the two key factors in a great performance are whether anyone else could have played the role as well, and whether the character lingers after you’ve left the theater. In both categories Johansson earns perfect scores.

On the exhaustive (and exhausting) awards party circuit in the past few weeks, I’ve heard many people praise “Her” and her (i.e., Ms. Johansson). However, they speculate that “some people consider it’s only half a performance.” (I’m not kidding, I’ve heard those exact words several times.)

But look at Judi Dench in “Shakespeare in Love” or Beatrice Straight in “Network.” Each woman was onscreen for less than 10 minutes, but won Oscars. Were those only fractional performances? I consider them mega-performances because they created full, rounded characters with limited screen time.

Jean Dujardin, Jane Wyman and John Mills won Oscars for films where they didn’t talk. Anne Hathaway and Joel Grey won Oscars for singing, without speaking a line of dialog. Were those “half a performance”? Absolutely not.

There is no precedent for an Oscar nom for Johansson in the Warner Bros.-Spike Jonze film, but it’s the 21st century. It’s time to rethink things.

Some folks fear if Johansson is nominated, it would open the floodgates and the next step would be nominations for voice actors in animated films. Oh, horrors! What if Robin Williams (“Aladdin”), Ellen DeGeneres (“Finding Nemo”) or Eddie Murphy (“Shrek”) had been nominated? What if Andy Serkis had been nominated for his work in the “Lord of the Rings” movies or “Rise of the Planet of the Apes”? Somehow, civilization would have survived and some talented artists would have received their due recognition. And I doubt those kind of noms would have created a revolution in awards categories, just an expansion.

I can’t tell critics or members of voting organizations who they should vote for. But I CAN urge them to think outside the box. Johansson in “Her.” George Clooney in “Gravity” and Alfre Woodard in “12 Years a Slave.” Those two have limited screen time but they create vivid characters who are crucial to the films. They should be considered as well.

It’s the 21st century, gang! And, whether the actor’s face is seen or not, a terrific performance will endure. So why not recognize the accomplishment?