I’ll never forget my first cellphone. I got it when I was 13, and it was the definition of “basic,” but I remember it so well — namely, how it felt. I remember the feel of the buzzy vibration of notifications, the rubbery keypad and the padded click of the power and volume buttons.

How devices feel affects how people feel; it’s just as important in creating the user experience as color, size and shape — and it takes teams of experts who rely on research, technological advancements and years of study to make sure products feel right.

Haptic design past and present

Early phones like the one I’m talking about are mostly a memory, but device “feel” certainly is not. Haptics is about the feel of things, whether mechanical or virtual, when you interact with them. Engineering and designing how devices feel is an important part of the product definition and development process.

Back in the days of my first phone, mobile handsets came pre-set to buzz very audibly to get your attention, says Debanjan Mukherjee, lead sensor engineer and technologist at Google. “Most people paid less attention to the pleasantness, subtlety or rhythm of a vibration,” he explains. The smartphone revolution of the mid-aughts quickly changed that. “Developers started asking how software and hardware could be used together to notify users but also confirm an action or give a sense of confidence,” says Debanjan. Once people started heavily using touchscreens, this feedback needed to happen faster than previous hardware could keep up with. Because of this, haptic development has been evolving quickly both at large and at Google. And a lot has changed in a relatively short amount of time.

While people generally agree that higher frequency leads to “sharper” vibrations, user preference is often subjective. “In the old days, we gave a vibration around 200 to 300 Hertz because that’s where human skin is most sensitive,” says lead haptics scientist Hong Tan, who has spent most of her career studying how people respond to haptic feedback. “But I liken that frequency to a soprano voice — it’s very sharp, not everyone appreciates it.”