Idea generation processes are important for companies to develop new products and services, and brainstorming is a popular method for generating ideas in groups. However, it has been shown that negative group effects can occur during brainstorming sessions, especially since teams today often collaborate from different locations. Therefore, electronic brainstorming systems are needed that foster creativity while reducing negative group effects. We extend the research on electronic brainstorming systems by investigating how virtual reality affordances and constraints influence the occurrence of negative group effects in virtual reality brainstorming sessions. We conduct a qualitative study with 18 participants consisting of virtual reality brainstorming sessions and subsequent interviews. Using the affordance network approach, we explain the occurrence of production blocking and evaluation apprehension. Furthermore, we suggest extending this approach by incorporating constraintoutcome units and discuss whether the notion of affordance actualization can be transferred to constraints.