Affectiva Inc. sees a future in which every computer knows how you feel.

The Waltham startup has analyzed more than 3.4 million faces around the world and mined them for billions of ordinary expressions: wrinkled brows, widened eyes, lips pulled tight, and more. Its researchers have created algorithms that allow devices of all kinds — smartphones, tablets, and laptops — to identify the emotions under those expressions.

Read more here.