More interesting is the absence of the classical stereotypes in a digression on Gaul (15.12). This indicates that Ammianus was perfectly capable of avoiding the classical stereotypes. So how stereotyped is his treatment of non-Romans in the rest of his history?
The qualities repeatedly ascribed to the barbarians are furor (rage, anger) and ira (embitterment, rage). But these descriptions of groups and individuals hostile to the Empire are not of an ethnographical nature, because they are not national characteristics. Ammianus also applies these qualities as fallicia (cheat, fraud) and saevitia (cruelty) to Romans. That Ammianus ascribes the same sort of characteristics to both barbarians and Romans, shows that he did not intend to write an ethnographic account in the modern sense.
Wiedemann furthermore examines if comparisons with animals are evidence of how Ammianus saw certain ethnic groups. After all what makes a barbarian is his close link with beasts. Wiedemann notes that all animal comparisons illustrate negative qualities in the Res Gestae. A lot of barbarians - not all of them, the Persians being an exception - are described as wild beasts. This fits perfectly well into the classical rhetorical pattern of historical writing. Interesting, however, is that also some Romans are compared with animals. And Ammianus even considers Christians worse than animals: "no wild beasts are so hostile to humans as the majority of the Christians are to one another" (22.5.4).
Barnes (1998) notes that Ammianus usually uses beast metaphors to illustrate the behaviour of a specific individual, and not a `wild nation'. They are applied to any person he disapproves of, non-Romans and Romans alike. Most of the time he disapproves because of personal or religious reasons. Beastly behaviour is not a special mark of barbarians. These characterisations usually give voice to a deep personal animosity rather than to ethnographic typifications. The moral dimension is undeniable.Wiedemann concludes his article by saying that Ammianus did not intend his digressions to be descriptive ethnography. Some barbarians as well as some Romans threatened the imperial order and Ammianus treated them alike in negative terms. Barnes agrees and says that Ammianus shows his dislike of individuals with unusual frankness and a firm moral verdict. He often condems his `enemies' with animal imagery to reinforce the verdict.
Matthews (1989) deals with the subject of barbarians quite differently. He gives a survey of Ammianus' treatment of respectively the Alamanni (16.11) and the Goths (22.7 and 31.7-8), settled farming peoples of Germanic origin: the Huns (31.1) and the Alani (both 31.2) and lastly the insurrections of the Isaurians (14.2) and the Moors (27.9). Matthews, also using archaeological and other written sources for constructing a composite picture of these barbarian peoples, concluded that Ammianus, even though it is not his central interest, does reveal many aspects of the social and economic situation of these peoples.