Caffeine increases alertness and improves reaction to moving targets

That morning coffee might be even more helpful than you think.


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There is evidence that caffeine improves several visual and cognitive skills. However, no studies have investigated the acute effects of caffeine on dynamic visual acuity (DVA). In a new study, scientists at the University of Waterloo explored caffeine’s effects on dynamic visual skills. They found that caffeine increases alertness and detection accuracy for moving targets.

A person’s visual acuity is a person’s ability to detect and recognize small details. It can be measured under static (stationary) or dynamic (moving) conditions. In both conditions, visual acuity offers essential information about how we interact with the world around us. But, in particular, the DVA skills are especially important in the many daily activities in which we or objects around us are moving.

It is well known that caffeine increases the velocity of rapid eye movements. In this study, scientists determined how exactly caffeine enhances visual processing and facilitates the detection of moving visual stimuli by testing dynamic visual acuity.

Dr. Kristine Dalton of Waterloo’s School of Optometry & Vision Science said, “A lot of what happens in our environment is moving—like trying to cross a busy intersection as a pedestrian or finding something on a shelf as you’re walking through the aisles of a grocery store. Testing visual acuity under dynamic conditions can provide more information about our functional performance in these scenarios than traditional static visual acuity measurements alone.”

Twenty-one low-caffeine consumers participated in this study. On two different days and following a random order, participants ingested either caffeine or placebo. Scientists used a computer-based test to measure each participant’s dynamic visual acuity skills. The measurements were taken before and 60 minutes after caffeine ingestion.

Caffeine is a central nervous system stimulant that acts as an adenosine receptor antagonist. There is a considerable amount of research illustrating that caffeine ingestion modifies human behavior. The outcome agrees with many studies that proved that caffeine increases alertness and feelings of wakefulness and energy.

In this study, scientists found that participants who had ingested the caffeine capsules showed significantly greater accuracy and faster speed when identifying smaller moving stimuli. This indicates that caffeine positively influences participants’ stimulus processing and decision-making.

Dalton said, “Our findings show that caffeine consumption can be helpful for a person’s visual function by enhancing alertness and feelings of wakefulness. This is especially true for those critical, everyday tasks, like driving, riding a bike or playing sports, that require us to attend to detailed information in moving objects when making decisions.”

Journal Reference:

  1. Beatríz Redondo, Raimundo Jiménez et al. Effects of caffeine ingestion on dynamic visual acuity: a placebo-controlled, double-blind, balanced-crossover study in low caffeine consumers. DOI: 10.1007/s00213-021-05953-1


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