Learning

Learning is the process of forming associations that result in a relatively long-lasting change in the organism. Learning that involves relations between events is called associative learning, and the primary forms of associative learning are called classical and instrumental conditioning. Learning and memory are closely associated phenomena because memory occurs as a consequence of learning.

Older adults typically complain that their memory is not as good as it used to be, even though it may be their ability to learn that is actually most affected. Whereas their memories from the young adult period of their lives may be quite intact, older adults have greater difficulty remembering people's names or the items to pick up at the grocery store. This type of memory involves the formation of new associations and thus involves learning as well as memory. When a memory can be elicited, it indicates that learning has occurred. However, learning can occur and still not be demonstrated as a memory at a later time. The learning may have been poor in the first place (a common problem in normal aging), the memory may have decayed with time (over the older adults' life spans there is a much longer time period available for memory decay to occur), there may be injury or impairment in the brain (more likely in older than in younger adults), or the memory may be temporarily unavailable for retrieval because of the particular state of the person. For instance, older adults have sensory and perceptual deficits that affect memory test performance, and some also get more anxious and fatigued during testing than do younger adults.

Associative learning is most commonly investigated with classical (Pavlovian) and instrumental (Thorndikian) conditioning. Both paradigms involve exposing the organism to relations between events. The history of the study of classical conditioning is relatively long, beginning late in the nineteenth century. Although he received the Nobel prize in 1904 for his research on the physiology of digestion in dogs, Ivan Petrovitch Pavlov had already turned his attention to investigating formally the phenomenon of classical conditioning. Pavlov found that when he presented a neutral stimulus such as a bell shortly before he placed meat powder on the tongue of a dog, the bell would elicit a similar response to the response elicited by the meat powder. Namely, the dog would salivate when it heard the bell.

Instrumental conditioning was first systematically studied by Edward Lee Thorndike early in the twentieth century. In the case of instrumental conditioning, reinforcement (the consequence) is contingent upon the occurrence of a given behavioral response. For most of the twentieth century, techniques for the investigation of simple associative learning have been available, and these techniques have been applied to the study of normal aging and neuropathology in aging. Despite paradigmatic differences between classical and instrumental conditioning, the existing data in animal studies indicate that age-related differences in instrumental performance usually parallel those found in classical conditioning. In humans, there is far more evidence of deficits in classical than in instrumental conditioning.