[14] One of Sober's main fields of research has been the subject of simplicity or parsimony in connection with theory evaluation in science.
"[23] In his review of the book, biologist Ernst Mayr wrote "Sober has ... given us what is perhaps the most careful and penetrating analysis of the concept of natural selection as it affects the process of evolution".
[24] Sober has worked on clarifying and defending the idea of group selection; see, for example, his book with David Sloan Wilson, Unto Others – the Evolution and Psychology of Unselfish Behavior (1998).
Sober also has worked with the biologist Mike Steel, exploring conceptual questions about the idea of common ancestry.
And Sober has worked with the biologist Steven Orzack, clarifying and critiquing Richard Levins's 1966 paper "The Strategy of Model Building in Population Biology;" they also have worked together on the concept of adaptationism, and have devised a methodology for testing the hypothesis that two species exhibit a trait because they have a common ancestor, and not because natural selection caused each to evolve the trait.
He published a series of articles in this area with Malcolm Forster, the first of which was their 1994 paper "How to Tell When Simpler, More Unified, or Less Ad Hoc Theories Will Provide More Accurate Predictions."