[ His new friend talks, and eagerly taps his scientific illustration of Cthulhu, and something changes in John's expression. He shifts from faintly-frowning interest, attentive in a distant sort of way, to a spark of something warmer; it's the look of a man recognizing a fresh equation to solve. He folds his hands on the table, tapping his fingers against each other, and nods for Ford to continue. ]

I've seen it suggested that Pthumerians are influenced by human perception. But it seems like I missed out; I never did see Deerington.