Beware barely noticeable noises (quiet radio chatter, whispers in the next row, faraway applause). In a Cornell University study,
volunteers felt somewhat bored listening to (an objectively) engaging lecture, and didn't know why. The reason: a TV was left on in another room with the volume so low
they weren't even aware of it. On a subconscious level, subtle distractions hijack attention—which makes our slightly-less-focused selves feel more-than-slightly-less interested in whatever we're doing.
