Friday, August 20, 2010

The Science of Stress and Performance: Tiger Woods as a Hypothetical Case Example

One of the most popular stories over the past year has been the struggles of Tiger Woods, not only in terms of his complicated personal life, but also with regard to his professional downfall. Since his return to the PGA following his marriage problems, Tiger's golf game has not been close to the level his fans have been accustomed to seeing on a weekly basis. Most sports commentators and analysts have played the role of armchair psychologist by asserting that the cause of Tiger's poor performance is stress. This is a commonly used explanation for declines in professional performance, whether it be athletics or any other job. And rightfully so -- stress is well known to be a psychological experience that can negatively affect most elements of people's lives.

However, how exactly does stress negatively affect performance? And how exactly could it affect someone's golf game? I thought it would be both interesting and instructive to review some of the research findings on stress and how it can affect human functioning. In this case, I'm going to use Mr. Woods as a a concrete example of how stress could be affecting his performance on the golf course.

First off, let's define stress. Stress has actually been a difficult concept for psychologists to define, and no two definitions will necessarily resemble one another. For example, some people consider stress to represent something outside of the person -- something external -- that causes a negative reaction in the person. In this case, the stress could be a divorce or time demands. Other people define stress as the reaction itself. In this case, symptoms of muscle tension and worry are considered to be stress. To avoid getting into a long discussion over the best definition etc., let's just say that stress is the body's reaction to a demand in life, and the demands themselves can be called stressors.

Stress serves an evolutionary purpose. Stress is the body's way of preparing to act. Something happens in life that demands our attention, and so the body must prepare to react in some way. When people are under stress, the body releases hormones (ex: cortisol) that create arousal in the body (ex: increase in heart rate and breathing; muscle tension). Stress can be acute or chronic in nature. Acute stress is basically a demand that is short term in duration. For example, if you lose your job, but find a new one a few days later, this would be considered acute stress. If you are out of work for a period of months, this is chronic stress -- it is an ongoing demand. Both acute and chronic stress can affect our ability to function. In Tiger Woods' case, his stress is best defined as chronic because he has been dealing with multiple demands over a period of time (i.e., a pending divorce; struggling golf game).

So, how exactly does stress affect performance? And more specifically, how would Tiger's stress impact his golf performance?

There are two targets of stress -- the body and the brain. Let's start with the effects of stress on the brain. Stress is well known to negatively affect most aspects of human cognition; the key ones being attention, memory and decision-making. Stress hormones such as cortisol have the ability to cross the blood-brain barrier and impair how the brain functions. Also, stress is often accompanied by increases in worry and other forms of thought (ex: rumination; analytic thinking; problem-solving). There is only so much information that can get processed by the brain (often referred to as resource allocation). If your brain is occupied by all kinds of stress-related thinking, there will be fewer resources left for other types of information processing. In this way, the brain is like your computer's CPU -- if you have a bunch of  programs running at the same time, it's going to negatively affect overall efficiency.

Anyone who has played golf knows that there is a strong mental component to playing, and so attention,  memory and decision-making are important processes. Under high stress, people's ability to pay attention and concentrate is often minimized. In a game like golf, impairments in attention and concentration can be very problematic. And impaired attention often creates an unfortunate secondary problem -- problems with visual perception.

Visual perception (ex: accurately reading a green) is dependent, in part, on attention -- specifically, external attention. There are two types of attention: external and internal. External attention refers to focusing on things outside of our bodies, whereas internal attention refers to focusing on internal psychological and physiological experiences (ex: heart rate; thoughts).  Both forms of attention can be present simultaneously. For example, you can carry on a conversation with someone (requiring external attention) while thinking of something unrelated (internal attention). Thus, we can come up with a ratio that describes the distribution of attention at any given time. If you're devoting 80% outwardly and 20% inwardly, the conversation should be fine. But if most of your attention is directed inwardly, you're not going to be a pleasant person to talk with. There is a correlation between attention and perception, such that greater external focus of attention will lead to greater accuracy in  perception. Put simply, it is hard to accurately perceive something if you are not paying attention to it.

Accurate perception and ability to focus are obviously key to the game of golf. Once stress starts to interfere with attention, which subsequently affects perception, the results can be negative in terms of performance. However, this is not to say that Tiger Woods is experiencing serious impairments with attention or perception. His ability to focus and concentrate are some of his strengths, and his attention and perceptual abilities are still probably above average. The real question is this -- if his external attentional capacity has been reduced to say 75% from 90%, what effect would that have on his score across an entire tournament?

In terms of memory and stress, the latter can have a particularly negative effect on working memory. Working memory refers to the ability to hold a piece of information in mind in order to facilitate completion of another mental task. Working memory is what we use when we have to consider multiple pieces of information at once. In golf for example, while contemplating your strategy for how to best play a particular hole, you will simultaneously need to to hold one or more pieces of information in mind (ex: current wind speed; hole position) while making a particular decision (ex: club selection). As such, working memory and decision making will overlap a fair bit.

When it comes to decision making, the brain may have to store and manipulate multiple pieces of information at once. Using the computer CPU analogy from earlier, if you must consider multiple pieces of information, but have limited resources available, your ability to process information will be limited and perhaps inefficient. Also, there's greater risk of errors in decision making if the brain cannot process all the necessary information. Again, with someone like Tiger Woods, it is unlikely the case that he is struggling to process golf information. He has played the game his whole life and things that are well-learned are less affected by stress. Therefore, his ability to process information is still going to be greater than most players' ability. However, this does not mean that his working memory and decision making are completely intact. As most golfers know (myself painfully included), it only takes one or two relatively poor decisions to ruin a golf score.

The coping strategies that Tiger uses to handle the stress may also be affecting his golf game. For example, research shows that trying to suppress negative thoughts is not only ineffective under stress, but there can be rebound effects whereby the suppressed thoughts occur more frequently than what  was originally the case. If Tiger is simply trying to suppress certain negative thoughts while playing,  they could be recurring in his mind and acting as a distraction.

To show how these problems with cognition might play out during a round of golf, I'll use a concrete example that most golfers can understand and appreciate. While on the putting green, golfers must make use of multiple cognitive processes using multiple pieces of information in order to decide how to make their putt. It starts with attention and perception. The more distracted you are with inward focus, the more difficult it will be to focus externally on the green. And perception is key here. You must be able to see subtle shifts in slope and notice things like grass length in order to accurately perceive the true putting line. Also, while trying to focus externally, you will periodically have to hold certain pieces of information in mind (ex: wind; previous experiences on this green; what your caddy is saying) while making a decision. This whole process of thinking, perceiving and evaluating requires processing capacity in the brain. The more stress in the background of one's life, the less processing capacity available at a given time. Furthermore, this whole process requires some degree of patience -- unfortunately, impulsivity can increase under high stress loads as well.

As you can see, stress can make the mental side of the game more difficult. However, stress can also affect the body in negative ways as well, which may or may not be affecting Mr. Woods' game. Stress is often accompanied by physical symptoms. Perhaps the most common physical symptom of stress is increased muscle tension, which can obviously interfere with motor functions like swinging a club. Also, stress can interfere with both sleep quality and quantity. The interaction of muscle tension and troubled sleep often produces another physical symptom of stress (particularly chronic stress) -- fatigue. Stress also affects immune functioning, making people more susceptible to illnesses from viruses and bacteria, and can also have a negative effect on tissue repair. Indeed, recovery from injuries, including minor muscle tears, can be slowed by stress' negative impact on the body. Again, any one of these factors has the potential to impact performance -- including the performance of a great player like Tiger Woods.

As I have stated on more than one occasion in this article, the chronic stress in Tiger Woods' life may not be affecting him as severely as it might affect other people. He is an incredible athlete who knows the game of golf very well. And stress typically has fewer negative effects on activities we are very good at -- which is to say that stress probably affects Tiger's playing ability less than the average amateur golfer. However, when it comes to the world of professional golf, it only takes a few mistakes to significantly affect your score. And in this case, it is likely the case that the psychological and physiological effects of stress are playing a role in Tiger Woods' struggles.

I recently read that Tiger Woods is now thinking of changing his swing coach, in response to his problems on the golf course. My advice? He should perhaps consider consulting a psychologist.

Dr. Roger Covin
Montreal Psychologist
www.drcovin.ca

Notable References

Lupien et al. (2007). The effects of stress and stress hormones on human cognition: Implications for the field of brain and cognition. Brain and Cognition, 65,  209-237.

Walburn et al. (2009). Psychological stress and wound healing in humans: A systematic review
and meta-analysis. Journal of Psychosomatic Research, 67, 253–271.

3 comments:

Cathi said...

Thank you for your post. In your expert opinion, given the sequele of stress, why is it that there isn't more real education provided about it?

Thank you.
Cathi

Dr. Roger Covin said...

Well, I think there tends to be under-reporting about psychological issues generally speaking. But in cases like these specifically, there needs to be someone who knows the theory and research behind a particular issue, and then takes the time to make it accessible and concrete to the general public. University professors are your best bet to fill this gap, and they do -- but usually they're audience is a classroom, and not the public. This is partly why I wanted to write a blog -- to help take somewhat obscure psychological research and make it both accessible and understandable to readers.

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