I was looking for something lighter for a Sunday afternoon and came across this. I haven’t read the original paper, just a reference to it, but I reckon that ‘Orangoutang score’ is more fun than ‘random guess score’.
‘The Orangoutang score is that score on a standardised reading test that can be obtained by a well-trained Orangoutang under these special conditions. A slightly hungry Orangoutang is placed in a small cage that has an oblong window and four buttons. The Orangoutang has been trained that every time the reading teacher places a neatly typed multiple choice item in a reading test in the oblong window, all that he (the Orangoutang) has to do to get a bit of banana is to press a button, any of these buttons, which, incidentally, are labelled A, B, C and D.’
Fry, E. (1971) The Orangoutang score. Reading Teacher, 24, 360-2.