3Further Reading: Teller et al (1986)

4Recently some researchers have argued that we need to move away from this type of measure of acuity and consider 'hyper' or 'Vernier' acuity requiring, they argue, slightly higher cognitive ability. Even so there are other problems with the use of FP.

For the Technically Minded

: In the early days of using FP, researchers would often follow an operant conditioning paradigm. Psychologists have spent many years perfecting techniques of operant conditioning. When incorporated within clinical settings using operant procedures, FP often produced peculiar results. For instance, one of the authors once witnessed the following scene. An infant was brought into a lab and confronted with a large apparatus. Gratings versus grey squares were presented and if the child looked to the correct stimulus, a rabbit popped up, played a dance and beat a drum. Meanwhile the experimenter lurked behind the apparatus, occasionally popping up when he should have stayed down. The result was the child's conditioning took place, but not to the 'gratings then rabbit'. Instead it took place to the "grey square then laughing experimenter'. The child was diagnosed as blind, which only goes to prove that there are none so blind as those who will not see!