Replying to several research calls, I report promising results from an initial experiment which com-pares different negotiation support system approaches concerning their potential to reduce a user’s cognitive workload. Using a novel laboratory-based non-intrusive objective measurement technique which derives the user’s cognitive workload from pupillary responses and eye-movements, I experi-mentally evaluated a standard, a chat-based, and an argumentation-based negotiation support system and found that a higher assistance level of negotiation support systems actually leads to a lower user’s cognitive workload. In more detail, I found that an argumentation-based system which fully automates the generation of the user’s arguments significantly decreases the user’s cognitive workload compared to a standard system. In addition I found that a negotiation support system implementing an additional chat function significantly causes higher cognitive workload for users compared to a standard system.