Analytically oriented Negotiation Support Systems have been studied and developed for decades, but they have not become widely adopted by negotiation practitioners. Along with the phenomenal growth of e-commerce, a need has arisen for information systems that support the parties’ “soft” negotiation processes and communications in addition to the “hard” quest for a mathematically optimal solution. In this study, we report an experiment about applying three different communication modes in integrative win-win negotiations following the principled negotiation tactics. We focus on integrative negotiation’s dialoguing phase where the parties share information, brainstorm options together, and establish an appropriate atmosphere. We compare computer-supported same-time same-place negotiations aided by group support systems (GSS) - either anonymously or non-anonymously - with the control treatment group that uses verbal communication backed up with flipcharts and Post-it notes. Due to the recent social media revolution, the role of anonymity might have changed from the GSS research results obtained decades ago. Our goal is to find out possible differences in the negotiation outcomes: meeting satisfaction and productivity. We discovered that all three modes worked well when used together with a carefully structured and facilitated process, although the number of unique ideas generated was significantly higher in the computer-supported groups.