It was brains over brawn at the box office Friday night, as "Lucy" easily topped "Hercules" for first place.

The Scarlett Johansson thriller -- about a synthetic drug that massively increases brain power -- earned a bigger-than-expected $17.1 million.

"Lucy" cost a reported $40 million to produce, and will likely earn more than that this weekend. Johansson is having a banner year, having already appeared in the smash sequel "Captain America: The Winter Soldier" and the arthouse hit "Under the Skin."

Meanwhile, the Brett Ratner-directed "Hercules," starring Dwayne Johnson in the title role, had a rather weak opening. It muscled up $11 million for second place, and will likely earn around $28 million for the weekend. 

With Marvel's "Guardians of the Galaxy" opening next weekend, "Hercules" will have to look overseas to justify its reported $100 million price tag. It's already playing well in several key markets, including Russia. 

In third place, "Dawn of the Planet of the Apes" picked up another $4.7 million. So far, "Apes" has earned $160.3 million domestically and should have no trouble topping 2011's "Rise of the Planet of the Apes," which ended up with a $176 million domestic haul.

"The Purge Anarchy" continues to scare up big business. The low-budget horror sequel earned another $3.4 million on Friday, bringing its total to $44.7 million.

Rounding out the top five was Disney's struggling "Planes Fire and Rescue," which flew to $2.7 million yesterday. Its North American total stands at a low $28.5 million. Last year's "Planes" soared to a $90 million total, but the sequel won't come anywhere near that amount. 

Look for complete weekend estimates Sunday on HitFix.

Dave Lewis has been a Los Angeles-based entertainment writer and editor for nearly ten years. Originally hailing from Minneapolis, he moved to L.A. in 1996 to attend USC, before working for various periodicals and web sites including a lengthy stint at He joined the HitFix staff in 2011.