It is May 2, 2019 today, 24 days till my graduation. I can’t believe my four years’ life at college is already approaching the end. I can still remember the moment when I first arrived here, and that still felt like yesterday. What’s more, it is such a shocking thing when I realized that the beginning of 21^st century is already almost 20 years ago. I still remember when I was in primary school, whichever essay I wrote when thinking about the past would start with “Time flies”. However, there are also moments when one feels the time has frozen. There are so many times after I wake up from a long and complicated dream that I realized it was only 10 minutes since I last checked my phone. Also, whenever I finished writing up my exams and started going through all answers, I would find that one second in this situation was as long as ten minutes when I was actually writing the exam.

Does time really fly, sneaking from your notice? Does time sometimes freeze, leaving you nothing to do? Or does time actually flow at a constant rate, but our perceptions of it differ? Objectively we know that time goes by at constant rates, independent of what meanings and emotions we attach to it. But why do we perceive time to flow at different rates in different contexts?

One explanation of time lapse perception changes comes from changes in our internal clock (Droit-Volet & Meck, 2007). In this internal-clock model, an internal pacemaker records neural pulses and an accumulator judges the lapse of time by comparing the number of pulses. The comparator then compares the duration from accumulator with a sample drawn from reference memory, so that the relative time lapse could be determined (Gibbon et al., 1984). Neurologically speaking, cortical neurons in the striatum serve as the pacemaker, as are set to equal levels of activations in the beginning and different cortical neurons have different oscillation frequencies. Spiny neurons form the accumulator and comparator, which compares the pattern of activation stored in memory (Cordes et al., 2007).

Changes in the internal clock is brought by attention (Buhushi & Meck, 2006). This means that when we are not paying attention to the internal clock because we are focusing on processing something important, the internal-clock time will be slower than actual time. In this situation, we will think of the time as “flying”. Changes can also be brought by the changes in our arousal level. When arousal is high, the pacemaker accelerates, so it takes shorter time to reach the reference pattern of oscillation. Our arousal level is regulated by dopamine levels in the internal clock system, where an increase in dopamine speeds up the clock (Droit-Volet & Wearden, 2002). This means that when arousal is high, we tend to have more dopamine and overestimate durations, feeling that time flows slower than we think.

However, this does not seem to be somewhat different from real-life observations, as we always say happy hours are too short. What’s missing between neurological results and daily life? Emotion. Research has shown that it is actually the interaction between arousal levels and emotion valences that decide how you think time flows (Angrilli et al., 1997). When arousal is high, positive emotions leads to an underestimation of duration whereas negative emotions leads to an overestimation. This is explained by motivation and survival mechanisms, as negative situations require quicker responses, thereby speeding up the internal clock. In positive emotion states, the appetite motivation mechanism is triggered to savor a better experience, so duration perception becomes slower (Bradly et al., 2001). The reverse is true when arousal is low, where people tend to overestimate duration in positive emotions and underestimate in negative emotions. This difference is explained by attention allocation differences, as we tend to attend more to negative cues in negative mood, thereby paying less attention to the internal clock, making time “fly”.

References

Angrilli, A., Cherubini, P., Pavese, A., & Manfredini, S. (1997). The influence of affective factors on time perception. Perception & Psychophysics, 59(6), 972-982.

Bradley, M. M., Codispoti, M., Cuthbert, B. N., & Lang, P. J. (2001). Emotion and motivation I: defensive and appetitive reactions in picture processing. Emotion, 1(3), 276.

Buhusi, C. V., & Meck, W. H. (2006). Interval timing with gaps and distracters: evaluation of the ambiguity, switch, and time-sharing hypotheses. Journal of Experimental Psychology: Animal Behavior Processes, 32(3), 329.

Cordes, S., Williams, C. L., & Meck, W. H. (2007). Common representations of abstract quantities. Current Directions in Psychological Science, 16(3), 156-161.

Droit-Volet, S., & Wearden, J. (2002). Speeding up an internal clock in children? Effects of visual flicker on subjective duration. The Quarterly Journal of Experimental Psychology: Section B, 55(3), 193-211.

Droit-Volet, S., & Meck, W. H. (2007). How emotions colour our perception of time. Trends in Cognitive Sciences, 11(12), 504-513.

Gibbon, J., Church, R. M., & Meck, W. H. (1984). Scalar timing in memory. Annals of the New York Academy of Sciences, 423(1), 52-77.

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