A flow state typically occurs when a person’s abilities match the level of difficulty for the current task they are completing. During this state, researchers have found that most people who exhibit flow experience changes in blood pressure, muscle activation, and mental focus, among other responses. They also lose self-awareness and subjectively evaluate time as passing more quickly than usual. All of these factors relate to both the sympathetic and parasympathetic nervous systems, suggesting that flow may involve a non-reciprocal coactivation of both systems. Neuroscience and Psychology researchers in Stockholm, Sweden hypothesize that these effects suggest a potential physiological component that differentiates flow from other states of increased mental effort. This indication may provide accurate measurement of deep concentration in a flow state during various activities, including, but not limited to, music, video games, and writing. To test this hypothesis, the researchers had a total of 77 participants play a modified version of the video game Tetris and then complete a questionnaire about their experience. Participants were instructed to play three game difficulties: Easy, Optimal, and Difficult. In the Optimal setting, researchers adjusted the speed of the game to match the participants’ ability, based on initial performance. Speed was then decreased and increased by three stages for Easy and Difficult modes, respectively. Wireless ECG and Respiration data was recorded using the wearable BioNomadix amplifier (BN-RSPEC); surface electrodes were placed on the left and right chest. In addition, mental activity was measured in 35 participants—this was determined by frontal lobe oxygenation, which was recorded by placing the BIOPAC fNIR100 optical brain imaging sensor on the forehead of each participant. After completing all three video game difficulties, subjects were given a questionnaire to indicate their subjective experience with each game level. The results found that while larger respiratory depth was associated with deeper flow, there was no significant correlation between frontal cortex activity and flow.