Judgments of frequency and duration: One or two underlying dimensions?

How often and for how long a certain object was encountered are two distinct questions, requiring two distinct answers. But when humans judge an object to have been presented often, they usually also judge it to have been presented for a long duration. Under certain conditions the reverse is also true: When an object has been presented for a long time, humans think it has been presented often. These mutual influences hint at a single underlying...