By JOCELYN NOVECK

AP National Writer

So let’s start with the enticing premise of Luc Besson’s Lucy, starring Scarlett Johansson: Human beings only use 10 percent of their brain capacity. Imagine what it would be like if we could access all of it?

Well, wow. It would be sort of like … nothing new. Because, it turns out, in real life, humans pretty much DO use their whole brains.

DARN!

Now, we could choose to be annoyed that Besson starts with a total myth. Or we could give him a pass – because, hey, the movie is fiction anyway. The more relevant question, though, is how much of your own brain you should use when watching Lucy – a truly bizarre if often entertaining romp through, hmm, well, neuroscience, biochemistry, anthropology and basically the entire human experience, in 90 minutes. (Oh, plus a really cool car chase.)

And here’s another question: Just how much of his brain did Besson access when writing the dialogue? (That may sound nasty, but Mr. Besson, you’re the one who got us thinking about cerebral capacity.) The director knows his way around a camera, and you can argue about the merits of the storyline. But the dialogue often sounds like it was produced by a primitive computer: Hammy and clunky.

As for the name Lucy, it refers to the famous fossilized skeleton of a female estimated to have lived some 3 million years ago. Thank goodness that primitive woman has now evolved – into a bleached blonde, airheaded student of some sort, living in Taiwan. That’s where we meet Johansson’s Lucy, who at least seems more mature than her jerk of a boyfriend, who forces her to deliver a mysterious briefcase to a shady gang boss.

Turns out, it’s a drug delivery – a shiny blue crystal called cph4. Lucy and a few other unfortunates are the chosen mules, doomed to fly to Europe with packages implanted in their stomachs. Only, there’s a hitch. Roughed up by thugs, Lucy suffers blows to the abdomen, and the drug starts leaking into her system. Suddenly, she’s writhing uncontrollably – on the ceiling, no less.

And then things get really weird.

The drug’s effect is to enhance Lucy’s brain capacity. As it starts to climb – 20 percent, 30 percent, and so on – Lucy can suddenly speak Chinese. She can shoot six guys at a time. She can hear and see and feel – everything. She remembers being an infant. She calls her mother back home: “I remember the taste of your milk in my mouth,” she says, tearfully.

Because she’s becoming so smart – Lucy uses two laptops at a time, furiously unlocking the secrets of science – she knows that her condition gives her only 24 hours to live. Here’s where you shouldn’t get bogged down attempting logical analysis. As in, if Lucy can control movement and space and time, why can’t she expand the 24 hours? And really, why does she need to fly commercial to Paris?

Oh yes, Paris. Lucy heads there to meet Professor Norman, an expert on cerebral capacity (Morgan Freeman, in that gravelly voiced, level-headed role you’ve seen him play so many times). Simultaneously, she’s trying to recover all the drug packets, with the help of a police detective (Amr Waked) who really doesn’t know what hit him, but they do have an awesome car chase together. Professor Norman advises Lucy that, as she approaches 100 percent capacity – and death – she should do something useful with all the precious knowledge she’s acquiring.

And we really didn’t want to say this again, but: This is where it gets REALLY weird.

We won’t give away the frantic ending, and we’re not sure we could, even if we tried. At a certain point, the best strategy may be to just sit back, listen to the pounding music, admire those bright colors, and just shut that brain down entirely.