For more than a decade, neuroscientists have known that stress impairs memory performance—an effect likely due to the influence of stress-related hormones. A recent article in Science shows that a specific technique—taking practice recall tests—can help people overcome the memory problems associated with stress. And it even works if you aren't told how well you did when practicing.

For this work, 120 participants were asked to study lists of nouns one at a time. After studying the list, half of the participants engaged in a cognitive task known as “study practice” in which they re-studied the list by re-reading it. The other 60 participants engaged in a “retrieval practice” task, in which they tried to recall as many nouns on the list as they could, using practice tests. The retrieval practice participants did not receive feedback on their performance—they didn’t know if they were doing a good job of recalling the nouns or not.

One day after this memory related task, half of the study practice participants and half of the retrieval practice participants were subjected to a high-stress situation known as the Tier Social Stress Test, a procedure that placed them in a situation in which they will be harshly judged. The rest completed a non-stressful task of equal duration. The authors measured their physical state via a wristband that measured interbeat interval (heart rate) and blood volume pulse (arterial translucency) to confirm that the stress experience produced the expected response—which it did.

When the memory performance of the different groups was compared, three main results were apparent. First, the authors found that stressed participants who had studied by reading over the list of nouns recalled fewer items than their non-stressed peers. This finding clearly reiterates that stress resulted in memory impairment.

Second, the authors found that timing for item one was critical. There was no difference in memory performance for stressed versus non-stressed participants if the test was administered within five minutes of the stress experience. If, instead, the recall test occurred twenty minutes after the stress, there was a marked difference between the two different study methods.

This tells us that it took a fair amount of time for the hormones associated with the stress experience to have a significant effect on memory recall.

Finally, the authors replicated the differential recall effects. They found that participants who studied by re-reading the noun list recalled an average of 8.2 items five minutes after the stressful task, and an average of 7.9 items 20 minutes after the stressful task. By comparison, participants who studied by taking practice tests could recall an average of 9.9 items five minutes after the stressful task and could remember an average of 10.7 items 20 minutes after encountering their stressful task. This improvement came even if they didn’t know how they performed on the practice tests.

This data clearly demonstrates that the “retrieval practice” technique, in which participants completed practice tests, was more effective for memorization.

The authors suggest that the decline in memory that comes with time after the stressful encounter may be due to the biphasic nature of the stress response. The body responds to stress with two major hormonal changes. One is rapid, short-lived, and includes the secretion of epinephrine and norepinephrine. The second response is a gradual and longer-lasting secretion of cortisol. Though the authors did not test for levels of these hormones, they think their results are due to changes in cortisol levels that occur between five and 20 minutes after exposure to stress.

This work demonstrates that some techniques for memorization are superior to others, particularly in high-stress situations. Future work could examine this same phenomenon in a more natural environment, perhaps among emergency medicine residents who are training to deal with high-stress work environments daily. Regardless, for everyone who may need to learn material for upcoming recall tests, using practice tests to solidify your memory seems to be the way to go.

Science, 2016. DOI: 10.1126/science.aah5067 (About DOIs).