In 1963, Herbert Terrace wrote a paper describing an experiment with pigeons which allows discrimination learning to occur with few or even with no responses to the negative stimulus (abbreviated S−).
Terrace (1963) found that discrimination learning could occur without errors when the training begins early in operant conditioning and visual stimuli (S+ and S−) like colors are used that differ in terms of brightness, duration and wavelength.
Gradually, over successive presentations, the duration of the S− and its brightness were gradually increased until the keylight was fully green for 5 s. Studies of implicit memory and implicit learning from cognitive psychology and cognitive neuropsychology have provided additional theoretical support for errorless learning methods (e.g., Brooks and Baddeley, 1976, Tulving and Schacter, 1990).
In other words, Terrace has claimed that the "by-products" of conventional discrimination learning do not occur with the errorless procedure.
However, some evidence suggests that errorless learning may not be as qualitatively different from conventional training as Terrace initially claimed.
However, errorless learning attracted the interest of researchers in applied psychology, and studies have been conducted with both children (e.g., educational settings) and adults (e.g. Parkinson's patients).