Aubrey Johnson, former lead designer behind Color and Twilio, opined in a recent article:

“…hollow icons are more work for your users and ultimately create cognitive fatigue.”

Is that really true though? Our own Tim Wright gave me his take:

As someone who needed to google the phrase “cognitive fatigue,” I think Aubrey’s write-up raises some very valid points.

That being said, context is a more important thing to focus on when deciding on interface/design elements or treatments. Everything (mostly) has its proper place, and we don’t get into that weird gray area until things become a trend and start having rampant misuse in the community (see: border radius, reflections, torn paper, etc.).

The Web will be a much better place once we stop blindly taking design direction from the folks at Apple and focus on creating meaningful, usable and targeted experiences.