Designers must often work within constraints induced by other portions of their product. In this case, the touchpad had to be flush with the hand rest of the laptop, meaning there was no way to signal the user when he or she was moving a finger on the pad versus the inactive borders. The pad itself had to provide a tactile cue. From the post:
We studied a tremendous number of seemingly identical design variants of the dotted texture before we decided on the final version. Bumps varied by diameter, height, spacing, gloss, and even hardness. Every sample was evaluated by appearance and feel criteria. One test was to compare the surrounding palmrest texture to the pad samples to ensure that you could detect when your fingers moved beyond the pad boundries. We always did this with our eyes closed and then open. We also wanted to make certain the texture was pleasing to touch and look at. Many alternatives were rejected because they were too flashy looking, felt like sandpaper, or just made people giggle. In case you are wondering , we never considered making the pad yellow.
Sampling of prototype tactile samples
As the product got closer to release we were also able to test the texture with multiple users for extended periods of time. The feedback we gathered was very positive. They were able to detect the border easily and often commented that the subtle texture gave them a sense of precision as they moved their finger across the pad. The bumps provide indication of distance travelled and speed of movement. We found this effect to be of particular interest with multitouch gesture input.
I assume the thinkpad has “scrollbars” in their touchpad on the right side and on along the bottom. I wonder if the considered changing the texture for those areas so a user would know they could scroll. Of course, the scrollbars are only identified visually on most touchpads, and the user knows how to find them by moving a finger all the way to the border of the touchpad. With no raised border, users could still find a border by looking for the change between textured and smooth, and I’d be interested to watch how well they did this. A raised edge affords moving along it; it traps your finger into a straight line. I’d like to compare that to a texture change.