A limitation is that deeper processing, a major part of social change, has been challenged. Moscovici's conversion theory suggests that minority influence causes people to think more deeply about an issue, which leads to internalisation and lasting change. However, Mackie (1987) disagrees, arguing that it is actually majority influence that prompts deeper processing because people are surprised when the majority holds a view different from their own. If this is true, then a central element of the process of minority influence may be incorrect, undermining the theory's explanatory power.