Learning and memory under stress: implications for the classroom

Abstract

Exams, tight deadlines and interpersonal conflicts are just a few examples of the many events that may result in high levels of stress in both students and teachers. Research over the past two decades identified stress and the hormones and neurotransmitters released during and after a stressful event as major modulators of human learning and memory processes, with critical implications for educational contexts. While stress around the time of learning is thought to enhance memory formation, thus leading to robust memories, stress markedly impairs memory retrieval, bearing, for instance, the risk of underachieving at exams. Recent evidence further indicates that stress may hamper the updating of memories in the light of new information and induce a shift from a flexible, 'cognitive' form of learning towards rather rigid, 'habit'-like behaviour. Together, these stress-induced changes may explain some of the difficulties of learning and remembering under stress in the classroom. Taking these insights from psychology and neuroscience into account could bear the potential to facilitate processes of education for both students and teachers.

Figure 1

Systems activated in response to stressful events. On a stressful encounter, the autonomic nervous system (left) is activated within seconds to release catecholamines (e.g., noradrenaline) from the adrenal medulla and the locus coeruleus in the brain stem. Catecholamines are implicated in the ‘fight-or-flight’ response, but they also have profound effects on attention, working memory and long-term memory. Somewhat slower, the hypothalamus–pituitary–adrenal axis is activated, releasing corticotropin-releasing hormone (CRH) from the hypothalamus which stimulates the anterior pituitary to secrete adrenocorticotropic hormone (ACTH). ACTH in turn causes the adrenal cortex to produce cortisol and release it into the blood stream. Cortisol reaches peak level concentrations ~20–30 min after stress onset and readily enters the brain to affect cognition and behaviour. Cortisol feedback to the pituitary, hypothalamus and other brain areas (e.g., the hippocampus) prevents the system from overshooting.

Figure 2

The effects of stress on memory depend on the specific memory process investigated and the temporal proximity between the stressful event and this memory process. While stress (indicated as red flash) long before encoding impairs memory formation, stress shortly before or after the presentation of new information generally enhances subsequent memory performance. In sharp contrast, stress before memory retrieval impairs the recall of information learned previously which may directly affect performance at exams. In education, knowledge needs to be frequently updated by new facts or concepts relating to prior knowledge. In addition to its effects on memory encoding and retrieval, stress appears to impair this integration of new information into existing knowledge structures.

Figure 3

Stress impairs memory retrieval. Participants learned a two-dimensional object location task similar to the game ‘concentration’ (note that for illustrative purposes encoding is depicted by a book, similar to studying in class). One day later, participants either underwent a mild stress induction procedure (indicated by the red flash) or a non-stressful control procedure before recalling the card pair locations learned on day 1. Participants in the stress group recalled significantly fewer card pair locations on day 2 than participants in the control group (relative to their performance on day 1), indicating that stress before retention testing reduced memory performance. Adjusted, with permission, from ref. 63.

Figure 4

Stress reduces the integration of new information into existing memories. On day 1, participants were instructed to memorise different stories presented in short movie clips (note that encoding is illustrated by a book for illustrative purposes). On day two, participants either underwent a mild stress induction procedure (indicated by the red flash) or a non-stressful control procedure before they were presented with a questionnaire regarding the study material from day 1. Importantly, some items of this questionnaire included wrong information about the study material (misinformation, shown in orange). On day 3, forced choice questions were used to test whether the misinformation had been integrated into the memory trace of the study material. In the memory test, possible answers were the correct original information, the misinformation presented the day before and other incorrect answers (lures) that were not referred to on day 2. Overall, participants endorsed misinformation more often than lures, thus demonstrating a misinformation effect. Critically, stressed participants endorsed fewer misinformation items than participants of the control group, suggesting that stress reduced the modification of the original memory on day 2. Adjusted, with permission, from ref. 81. *P<0.005

Figure 5

Stress shifts the balance between multiple systems underlying learning and memory. At rest, this balance is tilted towards the ‘cognitive’ memory system depending on the hippocampus, allowing for the formation and recall of flexible memories. Stress, however, is thought to alter the system domination learning and memory. Under stress (indicated by a red flash), the balance tips towards more rigid ‘habit’ memories encoded by the dorsal striatum. Thus, stress affects not only how much is learned (memory quantity) but also what is encoded and how memories are built (memory quality).