They say that times flies when we’re having fun. And from all personal experiences, this seems to hold true. When bored, annoyed or just in a low mood, time seems to creep forward. In a boring lecture, you feel as if hours must have passed. The clock reveals that you are mistaken. Only five minutes have passed in reality.
When we are having fun, or are in high spirits, time seems to be running away from us. Instead of staring at the clock and realising no time has passed, all the time has passed! There we are, thinking we had hours left, when in reality, the fun will (have to) end in 5 minutes. Time’s up.
It does seem odd that our moods influence our perception of time. But according to neuroscience, this makes perfect sense. At least it seems to work for mice. Research by Soares et al (2016) trained mice to be able to estimate time intervals. The mice would be asked to indicate whether the time interval between two tones (T1, T2) would be longer or shorter than 1.5 seconds. Shorter would mean the mouse had to go to the left and stick its nose into a port. If it were correct, it got water a reward, to make sure it stuck with the task. If the mouse judged the interval to be longer than 1.5 seconds, it had to go to the right, and stick its nose into that port. Again, when right, it received water as a reward. Pretty simple right?
Now before we start getting in deep, there is endless debate between the overgeneralisation from one species to another, and sample sizes. Yes both the studies that I am about to describe had under ten mice in them. These mice also did 8513 trials. They were also pharmacogentically edited, or under the influence of optogenetics. So, although unsurprisingly not tested on humans, the research was done in such a way, and its results are such that I am happy to extend these findings to people also.
Let’s look at the first study then. The mice had been trained to be able to follow the task, and answer the question: “longer or shorter than 1.5?” well enough for some serious science. Now, in study 1, the mice get their dopaminergic activity suppressed through pharmacogenetic means. In simple English: these mice have been bred to have a gene, or a complete pathway, that is sensitive to a certain type of pharmacology (drug). When this drug enters the mouse, in this scenario the mouse becomes less sensitive to dopaminergic activity. The mouse as such can produce, uptake and re-uptake dopamine, but it makes little to no difference to the mouse. So, what does this do to its time perception? Well, if the mouse could even be asked to perform the task (no dopamine = no motivation!), it got the timing rather wrong. So, when dopamine is being messed with, it becomes rather more difficult to estimate whether an interval was shorter or longer than 1.5 seconds. At least, the mice got it increasingly wrong.
The third study might be of more interest to us humans (I am also blatantly skipping the second study, as it was check for the relationship between dopaminergic activity and movement within the mice). So, within the third study, dopamine neurons get switched on, an/or off, through the means of optogenetics. This means the mice have been bred to have genes or a pathway that is sensitive to light receptors. These mice specifically have a sensitivity that can inhibit or activate dopaminergic activity. Again, ethics won’t allow this type of testing on humans.
Now what happens if I switch off your dopamine neurons? Well, within the mice it led to the overestimation of time having passed. The clock was dragging its feet, and so where the mice. What happens when dopamine neurons are activated? The mice underestimated the time having passed. And were continuously estimating intervals that were over 1.5 seconds to be shorter than. Lucky this is a systematic estimation. The mice, when training for the task, were measured and an S-curve was built on their accuracy. Along the x-axis of the graph is time. The original curve sits in the middle, with an exact copy of itself to the left (dopamine activation) and to its right (dopamine inhibition). So it’s not as we saw in study 1 that mice become less sensitive and just plain wrong. No! There is a systematic skew in the perception of time. We do experience time as faster when we have more dopaminergic activity and slower when we have less. So there it is folks: Time really does fly when we are having fun!
So what does this mean? And what can we do with it? Remember, dopamine is important when it comes to motivation. When we underestimate time, we also increase the likelihood of the activity. The reverse is true if we feel as if hours doing a task have passed, but we have only been “at it” for about 20 minutes. So when you have a daunting, probably very long task that needs completing, make sure you stock up on some dopamine, or take enough exercise breaks to create it when you have depleted it doing the most boring thing ever!
References: Soares, S., Atallah, B. V., & Paton, J. J. (2016). Midbrain dopamine neurons control judgment of time. Science, 354(6317), 1273-1277.
