The ‘attention span’ concept is a historically recent, lab-derived construct.

Evidence

When we fret, now, about our “attention span,” we are fretting about our attention in terms given to us by THIS research tradition. The very idea of an “attention span” in a durational sense was an exact outgrowth of such studies (actually, earlier in the twentieth century the notion of an “attention span” referred not to duration, but to the actual visual field in which a stimulus might appear—it was spatial). Is THAT the attention we are fighting to take back from the frackers? — The Friends of Attention, Attensity!, 133

Categorization

• QUESTION: Verify: did ‘attention span’ originally denote visual field rather than duration? Worth chasing the citation.
• SEED: Article angle: ‘attention span’ as a manufactured category whose meaning shifted from spatial to durational — the phrase itself carries a false history.