New research explains why we sometimes find it so hard to ignore the sight of a delicious-looking drink.
If you’re a smoker who’s trying to quit, you’ll know that the sight of the smoking area where you used to share the latest gossip with your coworkers can trigger not just fun memories but also full-blown nicotine cravings.
Similarly, the sight and smell of food can trigger our appetite and make us want to eat more than we need. Neuroscientific studies have also shown that seeing an alcohol advertisement makes certain brain areas, such as the prefrontal cortex and the thalamus, hyperactive in people with alcohol use disorder.
Other studies in rodents have shown that environmental stimuli, or cues — such as certain buildings, objects, or places — can have strong effects on the brain. For example, in humans, exposure to these environmental cues may strengthen the memories we associate with certain behaviors, such as using addictive substances.
However, are our brains defenseless when we come into contact with these cues, or are our “central processing units” constantly hard at work, successfully keeping these distractions at bay?
Until now, it was unclear how much control our brains can exert over these stimuli, but new research looks under the hood and finds that we are, indeed, continually fending off unwanted reward signals that can trigger cravings and addiction. We do this by using our brain’s executive control processes.
Poppy Watson, from the University of New South Wales in Sydney, Australia, is the lead author of the new study, which appears in the journal Psychological Science.
Testing the brain’s self-control
The term “executive function,” or executive control, refers to the brain’s ability to solve problems, set and work toward goals, pay attention, stay focused, and regulate emotions, all while using cognitive functions, which include “cognitive flexibility, working memory, [and] inhibitory control.”
Working memory, or short term memory, allows us to hold information in our heads while we engage in other activities, for example, remembering a list of groceries when going to the supermarket.
In the new research, Watson and team wanted to see whether ignoring reward cues was harder if people also had to engage their working memory at full capacity.
So, the researchers devised an experiment in which the participants had to look at a screen that showed various shapes, including a diamond shape and a colorful circle.
The researchers told the participants that they would receive money if they successfully found and gazed at the diamond, but if they looked at the colorful circle, they would not receive anything.
Then, the researchers told the participants that differently colored circles meant different rewards for completing the diamond task.
So, a blue circle on the screen signified that they would earn a higher amount of money if they completed the diamond task, whereas an orange circle indicated less money.
As such, the diamond became the focus goal, while the colorful circle was the distracting reward cue.
Using eye-tracking devices, Watson and her team examined the direction in which the participants looked on the screen.
“To manipulate the ability of participants to control their attention resources, we asked them to do this task under conditions of both high memory load and low memory load,” Watson explains.
In the high memory-load conditions, the participants had to memorize a sequence of numbers in addition to completing the diamond task, so their executive control, i.e., focus, became highly divided.
“Study participants found it really difficult to stop themselves from looking at cues that represented the level of reward — the colored circles — even though they were paid to try and ignore them,” reports Watson.
“Crucially, the circles became harder to ignore when people were asked to memorize numbers: Under high memory load, participants looked at the colored circle associated with the high reward around 50% of the time, even though this was entirely counterproductive.”
Why stress makes it harder to go on a diet
The findings show, for the first time, that people need their full attention and cognitive control resources if they are to ignore environmental signals of a reward successfully. In other words, they also help confirm that self-control is a limited resource.
“We have a set of control resources that are guiding us and helping us suppress these unwanted signals of reward. But, when those resources are taxed, these become more and more difficult to ignore,” explains Watson.
“This is especially relevant for circumstances where people are trying to ignore cues and improve their behavior, e.g., consuming less alcohol or fast food,” the researcher adds.
The findings, Watson continues, also explain why people find it so much harder to kick a bad habit or quit an addiction if they are experiencing a lot of stress.
Conditions of high stress are the equivalent of the high memory-load version of the experiment wherein the participants had to remember and juggle several pieces of information at the same time.
“Constant worrying or stress is equivalent to the high memory-load scenario of our experiment, impacting on people’s ability to use their executive control resources in a way that’s helping them manage unwanted cues in the environment.”
“If you are under a lot of cognitive pressure (stress or tiredness), you should really try and avoid situations where you’ll be tempted by signals. You need to be in the right frame of mind to be in a situation where you can stop yourself from getting distracted and going down a path where you don’t want to go.”
Implications for addiction treatment
Scientists already knew that people find it hard to ignore cues of a large reward, but the new study shows that beating these cues requires our executive function and working memory. It also demonstrates that this is harder to do when we have to remember additional information.
These findings have important implications for treating addiction.
“Now that we have evidence that executive control processes are playing an important role in suppressing attention towards unwanted signals of reward, we can begin to look at the possibility of strengthening executive control as a possible treatment avenue for situations like addiction,” Watson says.
“Our research suggests that if you strengthen executive control, you should have better outcomes. Some studies have already demonstrated that training executive control can reduce the likelihood that you will eat chocolate or drink alcohol.”
Also, clinical studies have shown that “training attentional focus away from pictures of alcohol towards soft drinks [can] reduce relapse” in people with alcohol use disorder, she says.
However, the author cautions that we have yet to fully understand “the exact mechanisms” behind this, so more research is necessary “to figure out how exactly we can use executive control to our advantage.”