Nearly one-third of Americans say while they are at a store looking at product, they tried to find a better deal on their mobile device, according to a new report from GfK Roper, conducted on behalf of SapientNitro.

Thirty-three percent say while out shopping, they email or texted someone to tell them about an experience at a store, such as finding a deal or gift. Nineteen percent have used their phone to post something to Facebook, MySpace, Twitter or other social networking sites about their holiday shopping experience.

In addition, half or nearly half used their smart phones to find a store location (52%), research specific products they were thinking of purchasing (48%), browse for products (44%), and/or compare prices (40%). About one in three looked for discounts, deals, coupons, or discount codes (35%) on their mobile phones, or checked product availability at retail stores or websites (34%).

“Portability is a game-changer in transforming the way that people shop,” said Chris Davey, worldwide head of commerce at SapientNitro.

“Technology is causing some of the biggest shifts in human behavior that we’ve seen in years, and consumers are more informed and empowered than ever. This has a major impact not only on the way that consumers shop but also on the way that retailers need to market to consumers this holiday season.”

Among Americans who have started their holiday shopping:

*About half (53%) say they purchased a product in a physical retail store after researching the product online.

*Nearly half (44%) purchased a product online after shopping for a similar item in a physical store.

*Seven in ten (69%) say online customer ratings or reviews (such as on Amazon or Yelp) very or somewhat valuable.

*About half find e-mail promotions (50%) or online videos of product features/reviews (53%) valuable