Complex sentence: Although, in retrospect, this seems a rather straightforward insight, it was a significant step forward at the time, since until then research had been focused on attempts to develop very general-purpose problem solvers such as those described by Allen Newell and Herb Simon.
Split into simpler sentences: Although, in retrospect, this seems a rather straightforward insight, it was a significant step forward at the time. Until then, research had been focused on attempts to develop very general-purpose problem solvers such as those described by Allen Newell and Herb Simon.