Incidental Encoding

Overview

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

Long-term memory is a critical feature of human cognition, and it has been a prominent focus of research in experimental psychology. Many paradigms designed to tap long-term memory rely on asking participants to learn or study content, then test memory about that content. This is a good approach if one wants to understand how memory supports educational achievement, for example, where explicit study is part of the process. But, in day-to-day life, people often form new memories—many of which last for a long time—incidentally. People do not remember what they read in a magazine, the moment a partner was met, or the plot of a favorite story because they try to. Somehow, a good deal of experience just gets encoded into memory as life goes by. To study this side of long-term memory, experimental psychologists use something called an incidental-encoding paradigm.

The paradigm is especially useful for investigating the kinds of experiences that tend to produce strong long-term memories. Researchers think about experiences in terms of the kind of engagement they demand—personal, purely intellectual, deep, or shallow, for example. The incidental-encoding paradigm can be used to contrast long-term memory formation during different kinds of engagement by varying the cover task used to expose an individual to stimuli. A cover task is a task that a participant is asked to complete without knowing that memory for the stimuli in the task is tested later.

This video demonstrates standard procedures for using the incidental-encoding paradigm and two different cover tasks to investigate long-term memory when explicit study of a stimulus is not demanded.

Procedure

1. Stimulus and apparatus.

Run the experiment on a computer.
Collect a set of pictures of real-world, everyday objects (Figure 1).

Figure 1. Sample stimuli for incidental encoding. Typical experiments utilize color photographs of everyday objects, like the five shown here. Many labs make such stimulus sets publicly available. These examples are from a group at MIT: http

Results

An influential effect in the domain of long-term memory is that objects are more likely to be remembered when incidental processing is more elaborate, especially when it is personal. Memory performance in a surprise test is therefore usually worse among participants exposed to the letter ‘C’ task and age-matched participants exposed to the more personal “have you ever touched it” task. Figure 5 graphs this result, which suggests that encoding into memory is not a random process, b

Application and Summary

Incidental encoding followed by surprise memory testing is the primary vehicle of current research into the mechanisms of long-term memory formation, attempts to improve memory, and attempts to understand memory disorders like Alzheimer’s disease, in particular. It is well established that intentional encoding in Alzheimer’s disease is extremely impaired. For example, if patients try to remember stimuli, because they know they will be tested later, then they remember very little compared with controls. This c