The other thing is that full-color, textured icons help a great deal with immediate recognition as well. It's easy when the "open" icon is a yellow folder.
Sadly, the move to flat design with monochrome icon outlines destroyed that entirely. I'm still waiting for full-color icons to come back in style again. They can still be flat, but being filled with color (not just colored outlines) helps immensely with fast recognition.
The other thing is that full-color, textured icons help a great deal with immediate recognition as well. It's easy when the "open" icon is a yellow folder.
Sadly, the move to flat design with monochrome icon outlines destroyed that entirely. I'm still waiting for full-color icons to come back in style again. They can still be flat, but being filled with color (not just colored outlines) helps immensely with fast recognition.