Friday, February 24, 2012

Well, that wasn’t worth it: Effort discounting in the brain

Most of us have a complicated relationship with the effort required to get things done.  On the one hand, we generally prefer to do things in the easiest possible way.  On the other hand, there are times when the effort we put in to accomplish a goal becomes part of the reward itself.

From a biological standpoint, though, for most situations we are probably best off finding the least effortful way to achieve a goal.  That is, an animal that routinely puts in a lot of effort to get some reward (say, food) will be at a disadvantage relative to some other animal that puts in less effort to get the same reward.  So, we might expect that humans would have mechanisms that allow the amount of effort we expend to achieve a reward to affect the value we give to that reward.  

This question was examined in a 2009 paper in Cognitive, Affective, and Behavioral Neuroscience by Matthew Botvinick, Stacy Huffstetler, and Joseph McGuire.  They explored a phenomenon called effort discounting, which is just a fancy way of saying that the more effort that you put into something, the less valuable the reward associated with the effort. 

They had people do two simple tasks in an fMRI scanner.  On each trial, they saw a numeral (0 and 5 were never shown).  If the numeral was yellow, they judged whether the numeral was odd or even.  If it was blue, they judged whether it was greater or less than 5.  Sometimes, the study required low effort.  In low effort blocks, people did a series of trials on only one of the tasks.  Sometimes, the study required high effort.  In high effort blocks, the two trials were randomly mixed together.  It is hard for people to switch back and forth between judgments, and so these blocks were much more difficult than the blocks that all involved the same judgment. 

After each block of trials, people were told whether they received a one dollar reward.  They were told that the computer would decide randomly whether they got the reward and that the reward was not based on their speed or accuracy in doing the task.  They were also told that the level of difficulty of the task would not affect whether they got the reward. 

The authors measured blood flow in the brain (which is related to brain activity).  They were particularly interested in a brain structure called the Nucleus Accumbens.  This structure is deep in the brain in an area called the basal ganglia.  This brain area is known to be involved when people are evaluating rewards.

The authors found that this area responded much less to a cash reward when people just did a high effort set of trials than when they did a low effort set of trials.  Another brain area, the Anterior Cingulate Cortex was related to the amount of effort people put in.  And the more this area was active (signaling that people perceived higher effort), the less that the reward was valued.

There are a few important things to say about this finding.

First, the Nucleus Accumbens is a deep and evolutionarily old portion of the brain.  This means that the tendency to see rewards as less valuable when they required more effort is a central part of our psychological makeup.

Second, in general it really is a good idea for us to accomplish our goals in the simplest way.  If we always found elaborate ways to satisfy goals that could be satisfied more simply, we would spend a lot of time wasting effort and energy.

Third, in those situations where we value the effort, the journey is often more rewarding than the destination.  For example, if you remodel your own home, then you probably put in a lot more effort than you would have put in if you hired someone else to do it.  In this case, though, the process of doing the remodeling is also rewarding.  In addition, whenever you look at the final product, you will remember that effort.  Those memories can also lead to feelings of pride in your accomplishment. 

So don’t shy away from putting in effort, but remember that effort is best spent when it will lead to a great reward or when the effort itself is part of what is rewarding in the first place.

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