The horizontal axis, the abscissa, indicates what motivates and stimulates the curiosity in the first place. Is it perceptual—Berlyne’s word—meaning, is it aroused by something surprising (What on earth is that sound?), by something new (Who could that stranger possibly be?), or by something uncertain (This creature—marmoset or raccoon? I just can’t tell)? Or is the curiosity epistemic, meaning: Is it aroused by a very real and urgent need for new knowledge about something?
