Perception Of Time
If there was no time nothing that we can perceive would exist. Although our senses – sight, touch, hearing, smell and taste – work by utilizing specialized sensory receptors, there is no specific receptor for time. Yet we can obviously perceive it. However, our perception changes over time – no pun intended.
“From infancy onwards babies must come to grips with a world marked by recurrent time patterns, learning the length of time, or duration, associated with the various actions they experience every day,” says Professor Sylvie Droit-Volet, at the Social and Cognitive Psychology Laboratory (Lapsco) at Blaise Pascal University in Clermont Ferrand, France. “They react, become agitated or cry, when something they expect does not occur on time: when the mobile over their bed stops turning earlier than usual, when their mother takes too long preparing a feed”.
Very young children “live in time” before acquiring an ability to be aware of its passing. They can only estimate time correctly if they are made to pay attention to it, usually be experiencing time in through how long it takes to do something. “For a three-year-old, time is multifaceted, specifically related to each action,” Droit-Volet explains. At the age of five or six a child is able to associate and amount of time with a particular action. “They begin to realize that a single time continuum exists separately from individual actions.”
The maturation of the prefrontal cortex causes children’s awareness of time to improve during childhood as children’s attention and short-term memory capacities develop. To estimate the time required to complete a task, they must pay attention to it they must also memorize a stream of time-data without losing concentration. Therefore, children suffering from attention-deficit hyperactivity disorder tend to have trouble estimating time correctly.
Accuracy can be improved by counting time. “A five-year-old cannot count the passing of time, but can do so if prompted by an adult. But their counting does not really keep pace with the seconds. At the age of eight, children start counting time on their own, keeping cadence, but not till they are 10 will they count time regularly and of their own accord, without input from an adult,” Droit-Volet says.
As a result of the development of an ability to estimate passing time at an early age, researchers suggested in 1963 that time, as perceived by our brains (subjective time), was synchronized with the ticking of an internal clock, in a similar way that our daily lives are tracked by the ticking off the clock (objective time). The researchers developed a model for measuring time. It consisted of a pacemaker continuously admitted pulses (ticking) that were stored in an accumulator. The subjective duration of time depended on the number of pulses that had accumulated (from the beginning of the stimulus). When the internal clock was made to speed up, the number of pulses increased and thereby created the impression that time was passing more slowly.
Further, if you were to stop paying attention to time, the pulses would be blocked and would not reach the accumulator. The pulses were not counted, so time appeared shorter than it really was. Although the internal-clock model helps us to predict the behavior of people participating in psychological research, it is only a metaphor and cannot be used as a scientific indicator of brain physiology or anatomy.
Since then, Professor Warren Meck, at the Duke Institute for Brain Science, North Carolina, developed a more physiologically realistic model. According to the striatal beat-frequency model of interval timing, the representation of time is underpinned by the oscillatory activity of brain cells in the upper cortex. The activity of each oscillator cell is characterized by a specific rhythm. “Each of these brain cells has up to 30,000 connections with a series of cells in the cortex oscillating at various frequencies. The neurons in the striatum can read time codes emitted by oscillator cells in the cortex. They come into action when oscillatory activity corresponds to previously detected patterns, stored in memory,” Meck explains.
“For durations ranging from a few milliseconds to several minutes, the processing of explicit and implicit timing does not bring into play the same neuroanatomical regions,” says Jennifer Coull, a senior research fellow at the Cognitive Neuroscience Laboratory, at Provence University in Marseille. It has also been shown that the cerebellum plays a key role in motor tasks requiring perception of implicit timing. In addition, “the regions of the brain involved differ depending on the context, particularly if the stimulus only lasts for a very short time, less than 200 milliseconds,” says Coull.
The researchers also discovered that the brain’s perception of time involves processes linked to memory and attention: for example, feeling like time is passing more quickly when we are busy or doing something exciting. However, by contrast, minutes drag by when we are bored, for example, when we are standing in line.
“On account of the joint contribution of memory and attentional processes, processing by the brain of time-related data can only be based on a functional network, rather than a single region. This certainly explains why there are no neurological or psychiatric disorders characterized exclusively by temporal processing deficits,” Coull says.
Dopamine has been discovered to be the primary neurotransmitter involved in processing time. Dopamine agonists (compounds that activate dopamine receptors) tend to speed up our perception of time. This also occurs after consuming certain drugs (such as cocaine which enhances the effect of dopamine).
Emotions also play a role. In 2011 Professor Droit-Volet and Sandrine Gil, a lecturer on cognition and learning at Poitiers University, France, published research that examines how changes in the emotional state of the participants (caused by watching films) impacted their sense of time. The researchers showed students segments from films that were known to induce fear (horror movies) or sadness (dramas). A third category of “neutral” footage (weather forecasts) was also shown. After viewing the footage, the students were asked to estimate the duration of a visual stimulus.
“Fear distorted time, the stimulus being perceived as longer than it really was,” says Droit-Volet. Fear triggered a state of arousal that speeded up the rate of the internal clock. This also resulted in dilated pupils, higher pulse rate, increased blood pressure and muscular contraction. It appears to represent a defensive response triggered by a threatening situation. The researchers observed a similar tendency to overestimate time in three-year-old children exposed to a threat.
But, “quite unexpectedly, sadness does not affect our perception of time, no doubt because the emotion felt when watching a sad film is not strong enough to slow down physiological functions,” Droit-Volet explains.
Gil and Droit-Volet have also researched the perception of time when the face of someone close to them expresses a secondary emotion such as shame. Seeing someone that looks ashamed causes the observer to understand the reason for this feeling. “This reflective activity distracts attention from time-processing, so that estimated time seems shorter than it really is,” Droit-Volet says.
Droit-Volet says, “Our perception of time is very revealing of our emotional state. There is no single, uniform time, but rather multiple times which we experience. Our temporal distortions are a direct translation of the way in which our brain and body adapt to these multiple times, the times of life.”
Next article in this series: “Time Zones”