The presence of proxies, either animated or static images, positively affects users in the learning environment. Images of both static and dynamic agents are considered more plausible than the absence of images. Regarding the perception of an agent as a person, animated agents have a positive effect on static images.Lester, Kahler, Barlow, Stone and Bhogal (1997) found that the presence of animated instructional agents had a significant, strong and positive effect on students' perceptions of their learning experiences. In their study, middle school student participants encountered one of five "cloned" agents. These agents differed in the way they expressed themselves and in the level of advice they provided in response to the students' problem-solving activities.