Nevertheless, acquired behavioral traits can in principle be distinguished from inherited programs operationally: whereas many innate behaviors are displayed even in total deprivation of experience ("Kaspar-Hauser" experiments), learned behavior is always absent under such circumstances. Consequently, learning can be defined as the process by which an organism benefits from experience so that its future behavior differs from that of a comparable organism lacking this experience.
Typically, studies of learning compare the behavior of two subjects at two times. At a time t1 the individuals share the same experience and thus do not differ in performing the behavior in question. At a later time (t2), the behavior of the same subjects is compared again: one of the subjects has in the meantime been exposed to the experience of interest (most commonly the presentation of one or several stimuli), whereas the other was spared this particular exposure and instead received a control treatment. Learning is assessed according to the difference in the behavior of the subjects in t2.
By convention, learning is classified operationally into three types of stimulus presentation between t1 and t2:
Since the present work is concerned with a comparison of classical and operant conditioning, these are examined more closely.