Some phases of the psychology of puzzle learning
A 1915 psychology study of puzzle learning, written by John Hudson Ballard and published in New York by the Christian Alliance Publishing Company, aimed at readers of educational psychology. The first plate is a numbered sheet of photographs and diagrams showing a bird, a tree, interlocking metal puzzles, a key-like object, and concentric square mazes, while the second is a single line drawing of a cut-up square dissection with numbered pieces. A designer could take from them the look of early twentieth-century scientific plates: numbered callouts, plain line-art geometry, and grid-based maze patterns.
