Surfing the Inverted U-shaped Curve

I spent my frenetic summer longing for the sweet, rainy rest of fall and then spent September wondering how I remembered fall as being restful rather than stressful…

You may be familiar with the Inverted U-shaped Curve of the relationship between mental or physiological arousal/stress and performance – basically, that some stress improves performance but too much can worsen it. This was first described by Yerkes and Dodson in 1908 (and thus known as the Yerkes-Dodson Law), and was found to be true in their experiments for difficult tasks, but not simple ones (for simple tasks, performance continued to increase with increased stress – it should be noted that the stressor in the original rat experiment was electric shock).

The human research on stress has focused largely on the negative effects of stress (on cardiovascular health, for example) and on how to reduce stress using various interventions. This makes sense – our bodies use stress mechanisms evolved for acute threat (a lion chasing you), and the chronic use of these systems (from stressors like “I can’t pay the bills” or “I’m not getting along with my spouse”) places an enormous burden on them.

However, there has been some interesting work suggesting that, in fact, what doesn’t kill you may make you stronger. In this longitudinal study, it was found that having some lifetime adversity correlated with better self-reported mental health and well-being outcomes than having high levels of adversity or none – and this group also was the least affected by recent adverse events. This fits with a body of research (cited in this study) supporting the idea that exposure to a level of stress that you can handle improves your resilience to future stress.

In educational and clinical work, we usually operate on the principle that growth and learning happen at the edge of comfort and discomfort – in other words, with a moderate level of stress. Key to this work is the availability of a safe, guiding other person. In the concept of the Zone of Proximal Development introduced by psychologist Lev Vygotsky, this is a more knowledgeable other (peer or adult). This theory has been widely applied in educational practice as scaffolding, in which the student works on skills they can only do with support, and then the support is gradually removed as independent mastery of the skill is demonstrated. In clinical work in mental health, one of the goals is often to widen the client’s window of tolerance for emotional distress – and this is frequently done by allowing the client to “borrow” the therapist’s wider window of tolerance when working with a stressor.

The idea that there is an optimal level of stress that improves performance is not a recent one, but there is now an emerging body of evidence to suggest that how we think about the stress that we experience can determine how it affects our bodies.

An engaging 2013 TED Talk by Psychologist Kelly McGonigal (“How to make stress your friend”) highlights some of this research. She cites this study showing that experiencing a lot of stress OR believing that stress affects your health are both independently associated with worse health and mental health outcomes, and experiencing a lot of stress AND believing that stress affects your health together is associated with a 43% increased risk of mortality. This is an interesting association, but even more compelling is this study in which participants were given a social stress test (public speaking with the audience giving negative non-verbal feedback), with one group given instructions to reappraise (or reframe) stress as improving performance. The group that was taught to think of stress as aiding performance showed a healthier cardiovascular profile and less bias towards threat.

A more recent study similarly found cognitive and emotional benefits of a stress-is-enhancing mindset relative to a stress-is-debilitating mindset, in addition to sharper increases in anabolic ("growth") hormones, and in this study, participants in the “arousal improves performance” condition performed better on a GRE math test section in the lab and then actually had higher scores on their GREs in real life, outside the lab!

Stress and Social Engagement

In her TED Talk, McGonigal also draws attention to the fact that oxytocin is released as part of the stress response, motivating you to seek support. In this study, participants who experienced social stress did display social approach behaviour (trust, trustworthiness, and sharing). Oxytocin is protective for the cardiovascular system, reducing inflammation, relaxing blood vessels, and helping heart cells regenerate (at least in rodents), although it’s not totally clear if the cardioprotective effects are buffering or more in relation to recovery from stress. Social connection may translate into real long-term protection from the ill effects of stress - McGonigal cites a 2013 study showing that increased stress in the past year was associated with an increased risk of mortality, but not in people who reported spending a lot of time helping friends and family.

Let’s return to the idea that growth and learning happen at the edge of comfort and discomfort, with the support of a safe, guiding other.

Perhaps the involvement of the social engagement system is critical for being able to ride that edge? If we pick up on cues that make us feel safe and socially connected, there is a decrease in heart rate, increased oxytocin release, improved buffering or recovery from cortisol, and our response to the stress we experience will be more adaptive (behaviourally and physiologically). Interestingly, stress reappraisal also involves re-evaluating something that we thought was dangerous and deciding it is safe.

Imagine, instead, that you do not feel safe in a particular environment or with a particular person – will you be able to reframe task-related stress as enhancing? Your Zone of Proximal Development and your window of tolerance would likely be narrower; your “edge” might retreat inside your comfort zone. In fact, there is evidence to suggest that, rather than oxytocin uniformly promoting social bonding, it may increase the sensitivity to social cues, which can determine how adaptive the stress response is. When social cues in the environment are interpreted as safe/positive, oxytocin may promote social engagement and adaptive stress responses, but when the social cues are interpreted as unsafe/negative, oxytocin may promote negative perceptions of others and induce defensive behaviour and less adaptive stress responses. Populations who already had a negative bias in social interactions (e.g. those with severe attachment anxiety) were more likely to experience the “anti-social” effects of oxytocin.

A stress-is-enhancing mindset can be a powerful tool with which to surf the inverted u-shaped curve, if used within a broader context of safe relationship. This is especially important for those who are least comfortable in social situations. As you are navigating the stress you experience, or support others in their times of stress, can you think about how to cultivate a sense of safety at the same time as adopting/encouraging the reframing of stress as beneficial?