The Use and Capture of Images for Computer-Based Learning II - Section 1:

"There is also evidence that text should sometimes be used to support pictures as well as the converse (Holliday, 1976; Weidenmann, 1989; Bernard, 1990). Bernard (1990) went on to consider two strategies for increasing the effectiveness of illustrations in text. Two types of caption were used:

Descriptive - the caption repeated the contents of the picture
Instructive - the caption included key features of the picture. "
- posted by Yik Sheng @ 5:04 PM