This study analyzes consumer purchasing behavior by introducing voluminous product information into a consumer decision-making model. We focus on the case where consumers and firms have insufficient preferences for product attributes. This situation can apply to the case where a new product or product with new features is introduced into a market. We analyze consumer dysfunction in the presence of excessive alternatives and investigate how many products and product attributes are offered when selling a product. Following the ideal point model, we construct a new model and investigate it. Furthermore, by relaxing the assumptions made in the theoretical model, we numerically investigate and verify the robustness of our theoretical results. The results reveal that consumers may not be able to choose the best product because of confusion and dysfunction of their preferences for product attributes. This confusion causes consumers to choose each product with equal probability.