There are two principal ways that a model can be selected against: it can be largely ignored or it can be attacked. If a model is ignored, it goes extinct through being infertile: it leaves no descendants. If a model is attacked, it goes extinct through being killed off. If a model is ignored, it is regarded as being inconsistent with models about which users are more certain, but as being no threat to those models. If a model is attacked, it is perceived as being both inconsistent with, and a threat to, those models used with more certainty. Such attacks can be understood as (social-semiotic) immune responses by the community organised by the models perceived to be under threat, as will be explained below.