‘Dumb’ Laughs = a Smart Payoff : Box office: Jim Carrey vehicle pulls a ‘Gump,’ taking in $16.2 million on an otherwise slow film-going weekend.

By never underestimating the American public, the puerile comedy “Dumb and Dumber,” starring Jim Carrey, found prosperity through stupidity on its opening weekend. As was demonstrated by “Forrest Gump,” dumb sells, and “Dumb” sold a numbing $16.2 million in tickets at 2,447 movie screens.

Otherwise, film attendance was about par with last year, as theaters struggled valiantly to break out of the post-Thanksgiving stupor. The weekend’s only other nationwide debut, “Speechless,” a romantic comedy starring Geena Davis and Michael Keaton, had little to shout about with only $4.1 million on 1,404 screens and a fourth-place finish, according to preliminary estimates.

Two other limited releases, Jodie Foster’s star turn in “Nell” and Gary Oldman trading in his Dracula duds for Beethoven’s cutaway in “Immortal Beloved,” both got off to only OK starts, doing about $30,000 a theater. “Nell” was on two screens, “Beloved” on four.

Carrey, who apart from Tom Hanks must be 1994’s biggest star, made it three-for-three this year. “Dumb,” for which he received a smart $7 million, follows on the heels of “Ace Ventura” and “The Mask.”

New Line distribution head Mitch Goldman couldn’t help crowing that the sophomoric exercise’s freshman weekend took in almost as much as “Dumb” cost to make (only $18 million, despite the big bucks for Carrey). And his $16.2-million estimate is conservative, Goldman said, which gives the film a shot at being the biggest Christmas opening ever, a spot currently held by “The Pelican Brief” which debuted to $16.8 million over the same weekend last year.

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Young males and families made up the bulk of the weekend’s theater audiences. “The Santa Clause” held on to second place with $8.6 million, helped greatly by being piggy-backed with sneak previews for “Jungle Book” on Friday and Saturday. Tim Allen and his reindeer have rustled up $107.1 million and should continue to keep audiences amused through the end of the year.

Disney’s other hearty performer, “The Lion King,” added another $1.9 million and is now at$291 million with a holiday business boost around the corner. Even the disappointing “Miracle on 34th Street” had enough seasonal appeal to round out the Top 10 with $1.3 million over the weekend, although it’s grossed only $14.1 million to date.

Most adult-oriented films were less popular over the weekend. Though it’s expected to rebound, the sexual harassment drama “Disclosure” doesn’t look to be another “Fatal Attraction” or “Basic Instinct,” despite the star pairing of Michael Douglas and Demi Moore. After a lower-than-expected $10-million debut a week earlier, second-weekend business dropped 27% to about $7.3 million and third place at the box office. Industry pundits are already doing the 20/20 hindsight bit with “Disclosure,” claiming Warner Bros. opened it at the wrong time of year, when adults are not going to movies, overlooking the aforementioned record-breaking debut of “Pelican Brief” last year. Still, when adults do return to the movies after the holidays, this might be the ticket.

Then again, maybe not. It’s shaping into a peculiar end to an otherwise great year for ticket sales. The big commercial titles that had opened around Thanksgiving, such as “Interview With the Vampire” and “Junior,” were expected to tide things over until Christmas Day. They’re not. “Interview” dropped to 11th place with $1.2 million over the weekend, although it has already grossed $97 million. “Junior,” which captured another $1.6 million and eighth place at the box office, has only $26.4 million to its name and will have to struggle to get to $35 million, a major disappointment.

“Star Trek: Generations” is not over yet, but early indications that it might reach $100 million have evanesced. Nonetheless, with $1.75 million over the weekend and in seventh place, “Trek” is now at $65 million and will rank as one of the season’s hits.

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On the action front, Wesley Snipes’ “Drop Zone” fell to $3.8 million (fifth place) in its second weekend for only $12 million to date. The lower-budgeted “Low Down Dirty Shame” will end up in the respectable column with $1.4 million over the weekend (ninth place) and $23 million so far.

Eight new films enter the already crowded fray over the next week. To make matters worse at the box office, Christmas and New Year’s fall on Sundays, eating into what are otherwise two strong holiday movie-going weekends.

Handicappers expect “Dumb” to fend off the competition, since it’s the only youth film (over 12 years old ) around, except for the coming action-adventure “Streetfighter” with Jean-Claude Van Damme. “Santa Clause” should also have a Merry Christmas, though other family choices will be nipping at its nose, including “Lion King,” the upcoming live-action version of “Jungle Book,” “Little Women” and Macaulay Culkin in “Richie Rich.” Adults may finally get out to see “Disclosure” or instead opt for the national debut of “Nell.”

And “Speechless” will have to fend off another romantic comedy, “I.Q.” starring Meg Ryan, Robert Altman’s fashion fluff “Ready to Wear” and Steve Martin in the antic “Mixed Nuts.”