Key Study: The effects of emotion (stress) on memory (Luethi et al, 2009)

Travis DixonCognitive Psychology

Ever had to do a speech and you suddenly forgot what you were supposed to say? This post and the key study it summarizes could explain why.

The following has been adapted from our exam revision book: IB Psychology: A Revision Guide (available here). This is relevant for the effects of emotion on cognition and the HL extension: the (positive) effects of technology on emotion and cognitive processes and the reliability of cognitive processes.

When we feel stressed our body releases a hormone called cortisol. The effects of cortisol on our cognition and behaviour have been extensively studied. One way that stress (and cortisol) may affect memory is that it could improve our memory of emotional information. This could be a useful survival feature because we want to remember situations and events that were highly stressful so we can learn from them. For example, if we’re almost attacked by a bear when we’re out gathering berries we want to remember where that happened so next time we’re in that area we can be alert and on-guard for any signs of danger. (For more on this, read about Buchanan and Lovallo’s study).

Brown mother bear protecting her cubs in a Finnish forest

The effect of emotion (and its release of cortisol) on improving our memory serves an important survival function, like allowing us to remember where danger lives. However, the effects might not be the same across all types of memories.

However, some studies suggest that the effects of stress and cortisol on memory might not be the same on all types of memory. 

Key Study Summary: The effects of emotion (stress) on memory (Luethi et al, 2009)

This study tested the effects of stress (and cortisol) on multiple types of memory. 35 adult male participants were randomly assigned to either the stress condition or the control group. The stress condition underwent the Trier Social Stress Test to create stress. This test lasts 15 minutes and includes giving a 5-minute speech in front of a group and also having to do difficult math without making a mistake. Cortisol was measured to ensure the participants were actually stressed from the experience. The results showed that stress had a strong negative impact on working memory, but did not appear to have an effect on declarative verbal memory (e.g. being able to say what you remember from a list of items). Stress also enhanced classical conditioning for negative stimuli, but not positive stimuli (meaning it’s easier to learn to fear negative things). One conclusion from this study is that the effects of emotion could vary across different types of memory. (Full study available here).

From an evolution and survival point of view, perhaps this makes sense. When we’re in danger and highly stressed, we don’t need to be engaging in complex thought tasks that require high levels of working memory. Our thinking is much more simple and intuitive, like “I need to run away!” Having enhanced conditioning for negative stimuli also makes sense because we need to learn about negative dangers. Positive things do not pose such an immediate risk. For example, we absolutely need to learn and remember where the bear lives, but where the berries are in the forest is not quite as important.

Critical Thinking Considerations

  • This study provides an excellent counter-argument for the explanation of fear on improving memory as it shows that the effects may not be the same across all types of memories.
  • This study was conducted on adult males. Are there reasons why the results might not be generalizable to females, or kids?
  • Are there any ethical considerations relevant to this study? Think about how it might have the potential to cause psychological stress and harm and how a particular guideline could be used to reduce these effects.

Exam Tips: 

  • The material from this topic can also be used to show how a hormone (cortisol) can affect behaviour (memory). It can also be used to support an evolutionary explanation of behaviour and the material on the next page can be used for the neuroplasticity topic.
  • The specific emotion you should identify is “fear” because even though stress has the same physiological response, it is not technically considered an emotion.
  • A good SAQ response will explain the positive effects with Buchanan and Lovallo, but will also briefly explain how prolonged cortisol may have a negative effect (without necessarily using further studies).


Luethi, M. (2008). Stress effects on working memory, explicit memory, and implicit memory for neutral and emotional stimuli in healthy men. Frontiers In Behavioral Neuroscience2. doi: 10.3389/neuro.08.005.2008