Transfer and Forgetting

I discovered a paper recently whose title is probably more interesting than its content: Unstable Memories Create a High-Level Representation that Enables Learning Transfer. Quite a thought—that the instability of memory could be advantageous for transfer.

Researchers conducted two experiments, asking participants in the first experiment to learn a word list and then a motor task and in the second experiment a motor task and then a word list. There were three conditions within each experiment: (1) the word recall and motor task had the same structure (see the supplemental material for how ‘same structure’ was operationalized here), (2) the two tasks had different structures, and (3) the tasks had no determined structure.

It’s Not “Transfer”, It’s Domain Similarities


In the first experiment, participants first learned the word list and then their skill at the motor task was measured over three practice blocks. When the word list and motor task were of the same structure, participants did significantly better across the three motor-task practice blocks. Similarly, in the second experiment, after the motor skill was learned, participants who then practiced the word list with a similar structure to the motor task improved significantly more than participants in the other conditions. This improvement on an unrelated though similarly structured task was measured as transfer, and it occurred in both directions.

Somewhat surprisingly, however, this transfer of learning between word and motor tasks (or motor and word tasks) was correlated with a stronger decrease in performance on the original task, when participants were tested 12 hours later. That is, subjects who learned the word list and then successfully transferred that learning to the motor task (because the tasks were of similar structure) showed a sharper decline in their word list recall than subjects in other conditions. The same results appeared in the experiment where subjects first learned the motor task and then the word list.

At first blush, this seems obvious. The subjects who actually transferred their learning saw their learning on the original task displaced by the similarly structured and thus interfering second task. But when researchers inserted a 2-hour interval between the original task and the practice blocks, this decline disappeared—and the transfer learning was no longer present. Thus, it seems that not only the similar structure of the two tasks but also the weakness of the memory for the first task were both responsible for the effective transfer learning. The authors put it this way:

By being unstable, a newly acquired memory is susceptible to interference, which can impair its subsequent retention. What function this instability might serve has remained poorly understood. Here we show that (1) a memory must be unstable for learning to transfer to another memory task and (2) the information transferred is of the high-level or abstract properties of a memory task. We find that transfer from a memory task is correlated with its instability and that transfer is prevented when a memory is stabilized. Thus, an unstable memory is in privileged state: only when unstable can a memory communicate with and transfer knowledge to affect the acquisition of a subsequent memory.

Forgetting, Spacing, and Transfer

This is intriguing. In some sense, this reinforces results related to the spacing effect. Spacing causes forgetting which causes “unstable memories.” When learning is revisited after a period of forgetting, it finds this unstable memory in a “privileged state”: a state which allows it to strengthen the connections of the original learning.

But the above also suggests that extending learning for transfer to other situations or to other concepts may be done optimally in concert with spaced practice. In other words, the best time for transfer teaching might be after a space allowing for forgetting.

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Josh Fisher

Instructional designer, software development in K-12 mathematics education.