Like dozens of other brick-and-mortar retailers, Nordstrom wanted to learn more about its customers — how many came through the doors, how many were repeat visitors — the kind of information that e-commerce sites like Amazon have in spades. So last fall the company started testing new technology that allowed it to track customers’ movements by following the Wi-Fi signals from their smartphones.

But when Nordstrom posted a sign telling customers it was tracking them, shoppers were unnerved.

“We did hear some complaints,” said Tara Darrow, a spokeswoman for the store. Nordstrom ended the experiment in May, she said, in part because of the comments.

Nordstrom’s experiment is part of a movement by retailers to gather data about in-store shoppers’ behavior and moods, using video surveillance and signals from their cellphones and apps to learn information as varied as their sex, how many minutes they spend in the candy aisle and how long they look at merchandise before buying it.

All sorts of retailers — including national chains, like Family Dollar, Cabela’s and Mothercare, a British company, and specialty stores like Benetton and Warby Parker — are testing these technologies and using them to decide on matters like changing store layouts and offering customized coupons.