Brainstorming is used to generate as many ideas as possible around a subject matter.  When evaluation is used during brainstorming and respondents judge each  others ideas this can curb the creative process. So it is important to  delay the evaluation process as long as possible. We try to work with a  written instruction to give direction to the creative process. The  interaction must be aimed at stimulating each others creative thought  process. After conclusion of the brainstorming phase an evaluation can  be held based on the ideas generated by the respondents. For example  based on the written instruction or by using criteria formulated by the  respondents themselves.