## 4 Discussion  
Tea and coffee are consumed by millions of Americans every day, but which has a higher impact on cognitive performance has not been conclusively determined. In this study, three different cognitive domains were investigated to assess coffee and tea products during a multi-day within-subject controlled study. While participants' self-reported responses did not indicate that they felt confident about their task performance while consuming either hot beverage, their behavioral and neural efficiency results did indicate significant group and drink differences. One of the main ingredients in both tea and coffee is caffeine. Caffeine is one of the most widely used neurostimulants [3; 39; 40]. Among adults, the daily intake of caffeine ranges from 166-336 mg/day [41]. A typical cup of tea can contain between 40-60 mg of caffeine per serving, and coffee can range from 19-177 mg per serving, with Americans averaging approximately two cups per day [3; 42]. Caffeine has subjectively been shown to improve performance and memory, reduce errors in tasks, speed up cognitive processing, and improve mood [43; 44]. Caffeine is able to improve concentration and attention by eliminating distractors and improving focus [45]. Further caffeine consumption can improve vigilance performance and reaction time [45]. Functional magnetic resonance imaging (fMRI) has been used to look at the effects of caffeine on cognition [46]. One study reported that caffeine alters neuronal activity in the dorsolateral prefrontal cortex (DLPFC) during working memory tasks [47]. However, there is no conclusive evidence on whether tea or coffee is better for improving cognitive ability. Specific ingredients such as cocoa flavanols and gingko and ginseng can be added to traditional tea and coffee to enhance their effects on cognition. Cocoa flavanols have been shown to positively influence cognitive performance through increased central and peripheral blood flow [48; 49; 50]. The increase in blood flow could improve performance for a wide range of tasks through increased attention, motivation or arousal [48; 51]. Ginkgo and ginseng have been shown to improve different aspects of cognitive performance [52; 53; 54; 55]. During the arithmetic task, behavioral efficiency showed an improvement across the blocks; however, there was no significant difference between the cognition-enhancing beverages and the traditional hot beverages. As expected, neural efficiency was higher during the simple arithmetic task compared to the challenging task. However, for the coffee group, the enhanced coffee significantly improved neural efficiency for the challenging math task compared to the traditional coffee. For the tea groups, there was no difference. The enhanced coffee contained both caffeine and cocoa flavanols, which have been shown to improve cognitive ability [3; 48]. Caffeine is able to improve focus and  
Figure 11: Comparison of neural efficiency in the Stroop task. The left graph indicates neural efficiency while participants consumed the enhanced drink. The right graph indicates neural efficiency while participants consumed the traditional drink. Whiskers represent the SEM. attention while cocoa flavanols are able to increase blood flow, which also affects attention [43; 51]. This indicates that enhanced coffee is better when performing mental computations compared to the enhanced and traditional teas. Tea traditionally contains less caffeine than coffee and therefore could require consuming more over a longer period of time to see an effect on cognition [42]. In the RVP task, for behavioral efficiency, we saw no distinct pattern across the blocks for both the cognition-enhancing beverages and the traditional hot beverages. However, for the neural efficiency, both the enhanced blue tea and the enhanced coffee increased neural efficiency across the blocks. Similar to the math task, the enhanced coffee contained both caffeine and cocoa flavanol, both of which have been shown to improve attention and focus [49; 50].