What Can Nonhuman Animals, Children, and g Tell Us About Human-Level Artificial General Intelligence (AGI)?

Human-level artificial general intelligence is one of the grandest challenges in science. All evidence should therefore be brought to bear. Here, I summarize highly relevant work from comparative psychology, human intelligence, and developmental psychology. The comparative research points to a set of abilities proposed to separate humans from other animals; then, especially from the human intelligence field and the concept of the general factor g, abstract relational reasoning singles out. Deeper considerations of g suggest how abstract relational reasoning may underpin human cognitive processing itself. Developmental psychology helps clarify what that may mean.