From http://james-g.com/2012/06/examining-idealism-part-3/ :

• Jaynes's The Mind Projection Fallacy (PDF)
• "to quote the philosopher Richard Joyce, from his book The Evolution of Morality:

Research reveals that “common-sense morality” does include certain claims to objectivity. One study (Nichols and Folds-Bennett 2003; Nichols 2004) looked at young children’s responses concerning properties such as icky, yummy, and boring and compared them with their attitudes toward moral and aesthetic properties. [...]

The children treated the instantiation of all properties as existentially independent of humans (i.e., before anyone was around, grapes were yummy, roses were beautiful, and so on), yet made a striking distinction between properties that depend on preferences and those that did not: Things that are yummy or icky are yummy and icky for some people, whereas things that are good are good “for real.” Having reviewed such evidence, Shaun Nichols (2004: 176) comes to this conclusion: “The data on young children thus suggest, as a working hypothesis, that moral objectivism is the default setting on common-sense metaethics.” […] Larry Nucci (1986, 2001) has even found that among Mennonite and Amish children and adolescents God’s authority does not determine moral wrongness. When asked whether it would be OK to work on a Sunday if God said so, 100 percent said “Yes”; when asked whether it would be OK to steal if God said so, over 80 percent said “No.” Such findings contribute to a compelling body of evidence that moral prescriptions and values are experienced as “objective” in the sense that they don’t seem to depend on us, or on any authoritative figure.