Stress and Learning
How Prolonged Stress Damages Our Ability
to Focus and Remember What We Study
We've all experienced moments when a dramatic, shocking event became indelibly imprinted into our memory, like a photograph. Some of us have also experienced times when high stress levels made it impossible for us to concentrate, study or successfully tackle a difficult exam. Yet others stay cool under pressure and calmly ace the hardest tests, their recall completely unimpaired.
How can stress make our memory and focus so much sharper sometimes and duller other times? Why do some people focus and perform better under stress while others go to pieces?
One key to the puzzle is surprise. When we're startled by an unanticipated stressful event the hormones orchestrating our responses are quick-acting - adrenaline (epinephrine) and norepinephrine (NE.) Norepinephrine is a stress hormone released by nerve endings throughout our bodies in response to novelty or a sudden shock. When a trucker next to us on the road hits his air horn and we jump, that's NE in action. When we sit in a boring class and something interesting suddenly grabs our attention, that's NE, too. NE helps us pay attention and consolidates memory.1 NE is also involved in learning fine motor skills2 like handwriting, sports and the physical challenge of playing musical instruments.
It's a different picture when we know the stressor is coming or when the stress is constant. In both of these situations the glucocorticoid cortisol plays a determining role. The glucocorticoids (GCs) make us worry.
Glucocorticoids like cortisol are designed to help us recover from stress. Short-term exposure to GCs appears to help us learn and remember. But the situation reverses and the GCs acquire a negative impact on learning and thinking clearly when we're exposed to them for long periods of time.3,4,5,6 Curiously, females are less vulnerable to this effect than males.7
- High levels of unavoidable background noise are a major stressor. A number of studies have shown that proximity to noisy airports and busy roads have a measurable negative impact on childrens' ability to concentrate, read and learn.8,9,10,11
- Violence is another major stressor for young children. Children unfortunate enough to live in violent environments on average have poorer school performance, more anxiety and depression and lower self-esteem.12
The hippocampus is the part of the brain involved in learning and memory. High levels of glucocorticoids are often associated with depression. Glucocorticoids can destroy hippocampal neurons; in major depression the hippocampus actually shrinks in size.13
Another important factor affecting our ability to learn and perform in stressful situations has to do with individual differences in cortisol fluctuations when responding to stress. There are two distinct patterns; each with opposite effects. (Remember: cortisol is one of the glucocorticoids.)
Some people confronted with a challenge produce unusually low amounts of cortisol. These people act the part of the hero who stays calm under pressure - where others would be running or hiding, they walk calmly into the face of danger. Let's call them "low-reactors." Others respond to stress by generating high levels of cortisol. These folks tend to be highly strung, shy and anxious. They run screaming from the face of danger. Let's call them "high-reactors."
Low reactors tend to have better academic, learning and test-taking performance under pressure. Their cortisol levels actually drop while they're taking an exam. High reactors are in the opposite situation. Their cortisol levels rise when they're under academic pressure, and their performance suffers.14 But there are also problems for the low reactors. They have more trouble paying attention and their low cortisol levels seem to be associated with a failure of behavioral inhibitions. Many attention-deficit-hyperactivity-disorder children (ADHD) have unusually low cortisol levels.15,16
Stress-control techniques appear to help. Even something as simple as whether a child tells him or herself that they will succeed or have problems solving a difficult task correlates with higher or lower cortisol levels and improved or impaired performance.17
One factor that distinguishes high and low reactors is the amount of traumatic stress that life has dealt them. Veterans with post-traumatic stress disorder (PTSD) tend to live with higher chronic cortisol levels than non-combat vets; not surprisingly the PTSD vets display more difficulty in learning and memory.18,19,20 This phenomenon has also been seen in non-combat PTSD victims such as rape victims.21
Stress, then, affects us all a bit differently. In general the more anxious one gets, the more likely stress is to damage performance. Cooler heads, calm under pressure, may have trouble paying attention when there's no drama. Stress responses are designed to help us cope with challenges and danger. Over- or under-reaction are both failures to adapt smoothly to challenges and can make learning unnecessarily difficult.
1. Southwick, S.M., et al. 2002. Relationship of enhanced norepinephrine activity during memory consolidation to enhanced long-term memory in humans. American Journal of Psychiatry. 159(8):1420-1422.
2. Cartford, M.C., Gould, T., Bickford, P.C. 2004. A central role for norepinephrine in the modulation of cerebellar learning tasks. Behavioral and Cognitive Neuroscience Reviews. 3(2):131-138.
3. deKloet, E.R., Oitzi, M.S., Joels, M. 1999. Stress and cognition: are corticosteroids good or bad guys? Trends in Neuroscience. 22(10):422-426.
4. Vedhara, K., et al. 2000. Acute stress, memory, attention and cortisol. Psychoneuroendocrinology. 25(6):535-549.
5. LePine, J.A., et al. 2004. Challenge and hindrance stress: relationships with exhaustion, motivation to learn, and learning performance. Journal of Applied Psychology. 89(5):883-891.
6. Lima, E., et al. 2002. Stress during ACLS courses: is it important for learning skills? Arquivos Brasileiros de Cardiologia. 79(6):589-592, 585-588.
7. Bowman, R.E., Beck, K.D., Luine, V.N. 2003. Chronic stress effects on memory: sex differences in performance and monoaminergic activity. Hormones and Behavior. 43(1):48-59.
8. Haine, M.M., et al. 2001. A follow-up study of effects of chronic aircraft noise exposure on child stress responses and cognition. International Journal of Epidemiology. (30)4:839-845.
9. Stansfield, S.A., Berglund, B., et al. 2005. Aircraft and road traffic noise and children's cognition and health: a cross-national study. Lancet. 365(9475):1942-1999.
10. Matheson, M.P., et al. 2003. The effects of chronic aircraft noise exposure on children's cognition and health: 3 field studies. Noise and Health. 5(19):31-40.
11. Matsui, T, et al. 2004. Children's cognition and aircraft noise exposure at home--the West London Schools Study. Noise and Health. 7(25);49-58.
12. Hurt, H., Malmud, E. 2001. Exposure to violence: psychological and academic correlates in child witnesses. Archives of Pediatrics and Adolescent Medicine. 155(12):1351-1356.
13. Bremner, J.D., Narayan, M. 2000. Hippocampal volume reduction in major depression. American Journal of Psychiatry. 157(1):115-118.
14. Richter, P., et al. 1998. Effectiveness in learning complex problem solving and salivary ion indices of psychological stress and activation. International Journal of Psychophysiology. 30(3):329-337.
15. Hong, H.J. 2003. Hypothalamic-pituitary-adrenal reactivity in boys with attention deficit hyperactivity disorder. Yonsei Medical Journal. 44(4):608-614.
16. King, J.A., et al. 1998. Attention-deficit hyperactivity disorder and the stress response. Biological Psychiatry. 44(1):72-74.
17. Lindahl, M. Theorell, T., Lindblad, F. 2005. Test performance and self-esteem in relation to experienced stress in Swedish sixth and ninth graders--saliva cortisol levels and psychological reactions to demands. Acta Paediatrica. 94(4):489-495.
18. Yehuda, R., et al. 2005. Learning and memory in aging combat veterans with PTSD. Journal of Clinical and Experimental Neuropsychology. 27(4):504-515.
19. Vasterling, J, et al. 2002. Attention, learning, and memory performances and intellectual resources in Vietnam veterans: PTSD and no disorder comparisons. Neuropsychology. 16(1):5-14.
20. Sachinvala, N., et al. 2000. Memory, attention, function, and mood among patients with chronic posttraumatic stress disorder. The Journal of Nervous and Mental Disease. 188(12):818-823.
21. Jenkins, M.A., et al. 1998. Learning and memory in rape victims with posttraumatic stress disorder. American Journal of Psychiatry. 155(2):278-279.