Caffeine is a substance that causes pharmacological changes in the human body. It is one of the most frequently ingested substances in the world, strongly rooted in cultures around the world in different forms. It is found in drinks such as coffee, tea and soft drinks, in chocolate and in medicines. The fact that it is widely consumed has sparked interest in the scientific community to research its effects on human health and functioning. Many people rely on a cup of coffee in the morning to the point that some people declare themselves addicted to coffee. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay. So, what effect does this cup of energy have on our cognitive function? Caffeine is a central nervous system stimulant that feels noticeably alert after ingestion. It makes a person feel more awake, less tired and provides increased energy levels within minutes. This is great for Monday mornings, for those who struggle to shake off sleepiness once they wake up in the morning, and for times when you need to work through the night. However, research has shown that habitual morning coffee consumption replaces the production of cortisol, a hormone naturally produced at high levels in the early hours of the morning to provide the body with a boost of morning energy. It has been shown that postponing having a cup of coffee until 9 or 10 am is better as cortisol levels would have dropped and therefore caffeine can now step in to boost someone's energy again. In addition to inhibiting cortisol production, caffeine intake is also associated with hyperactivity and feelings of anxiety. Research shows that, in excessive quantities, caffeine overstimulates the brain. Alertness and energy turn into agitation, which negatively impacts cognitive function by causing you to lose focus on what needs to be done. This happens when caffeine is ingested in very large quantities. In a study conducted on the effects of black tea on human performance (Rizwan 2017), the conclusion drawn was that consumption of black tea “accelerated performance, improved memory, reduced the number of errors in various cognitive tasks. . . Even in small quantities, drinking black tea can speed up cognitive processing. The subjects underwent a series of cognitive tests, and the results revealed that drinking black tea improved delayed recall, which can be explained by caffeine's ability to increase a person's level of alertness. Furthermore, the subjects who consumed caffeine were faster in the visual search task than their counterparts taking a placebo because caffeine increased their alertness and short-term memory. This view is further supported by a review carried out by McLellan TM, et al. (2016) who state that low to moderate caffeine consumption increases alertness, alertness, alertness, reaction time, and attention. However, they did not notice any improvement in memory. Another study, however, showed that regular consumption of coffee and black tea had a correlation with the prevention of cognitive decline, thus reducing the risk of Alzheimer's and dementia. This is only possible if taken in reasonable quantities, within the daily intake limit, as ingesting too much coffee can overstimulate the brain causing confusion. Please note: this is just a sample. Get a custom paper from our expert writers now. Get a custom essay The study on black tea consumption also found that caffeine had no.