Methods and apparatus to detect people are disclosed. An example apparatus includes a receiver to obtain respective light information for a plurality of segments of an image, each of the segments corresponding to a portion of a media exposure environment; a pulse identifier to detect a first human pulse pattern in the light information associated with a first one of the segments; and a grouper to determine whether the light information associated with a threshold amount of the segments proximate the first one of the segments includes the first human pulse pattern identified in the first one of the segments, and to generate a presence indication when the light information associated with the threshold amount of the segments proximate the first segment includes the first human pulse pattern.