This paper examines ideation variety as a measure of the extent to which a design solution space has been explored. We investigated one cognitive factor (cognitive style) and one cognitive intervention (Design Heuristics cards) and their relationships with students' ideation variety, both actual and perceived. Cognitive style was measured using the Kirton Adaption-Innovation inventory (KAI), while variety scores were computed using the metrics of Nelson et al.  and Shah et al. ; an adapted form of these metrics was also explored. A group of 132 sophomore mechanical engineering students generated ideas for two design problems (one with and one without Design Heuristics cards). They sketched and described their conceptual solutions in words and assessed the variety of their solutions after ideation. Linear statistical techniques were applied to explore the relationships among the variety scores, students' self-assessments of variety, cognitive style, quantity of ideas, and the presence of the Design Heuristics intervention. Our results show statistically significant correlations between students' perceived variety and their variety performance, and between cognitive style and both variety performance and student perceptions.