One explanation for these results is as follows. The first task requires the formation of a visual image of an F. The visual image probably has at least some picturelike qualition(ดูไม่ออก) (spatial or visual), so a spatial or visually guided response (pointing) would be interfered with to a greater extent than would a verbal response. In other words, the visual image is more disruptive of, and disrupted by, another spatial or visual type of task (pointing than by a verbal kind of task (talking). The converse is also true: Holding a sentences in memory (a verbal task) is easier to do with a concurrent visual/spatial task (such as pointing) than with another verbal task. Notice that pointing or talking do not differ (ดูไม่ออก) difficulty overall but vary in difficulty as a function of the task with which they are being performed. Brooks’s (1968) work supports the idea that images and words use different kinds of internal codes (as the dual-coding hypothesis suggests).