and "Katyusha". 1860s Russian folk tune "Korobeiniki" first appeared in Spectrum Holobyte's 1988 versions of Tetris together "Dark Eyes", "Polyushko-polye" and "The Birch Tree". Nintendo's Game Boy version also includes "Korobeiniki", as well as the Johann Sebastian Bach's French Suite No. 3 In B Minor (BWV 814), and an original track by Tanaka. "Korobeiniki" is used in most versions of the game, and has appeared in other games, albums and films that make reference to Tetris. It was also included in the SNES Tetris game, Tetris & Dr. Mario, Tetris DS and Blue Planet Software The Next Tetris (1999, PSX and Windows). Doctor Spin's 1992 Eurodance cover (under the name "Tetris") reached #6 on the UK singles chart. In the 2000s, the Tetris Company added as a prerequisite for the granting of the license that a version of "Korobeiniki" be available in the game. Cognitive effects Tetris can cause the brain to involuntarily picture Tetris combinations even when the player is not playing (the Tetris effect), although this can occur with any computer game or situation showcasing repeated images or scenarios, such as a jigsaw puzzle. While debates about Tetris's cognitive benefits continue, some researchers view it as a milestone in the gamification of education. The Tetris Effect is when people who may play games like Tetris see floating pieces. Studies by American Psychologist Richard Haier discovered in 1992 that the brain used less energy as players' gaming skills got better. The study showed that regular Tetris playing allowed the brain to perform more optimally, and even increased the thickness of the cerebral cortex. Prolonged Tetris activity can also lead to more efficient brain activity during play. When first playing Tetris, brain function and activity increases, along with greater cerebral energy consumption, measured by glucose metabolic rate. As Tetris players become more proficient, their brains show a reduced consumption of glucose, indicating more efficient brain activity for this task. According to one study, moderate play of Tetris (half-an-hour a day for three months) boosts general cognitive functions such as "critical thinking, reasoning, language and processing" and increases cerebral cortex thickness. Jackie Andrade and Jon May, from Plymouth University's Cognition Institute, and doctoral student Jessica Skorka-Brown have conducted research that shows that playing Tetris could distract from cravings and give a "quick and manageable" fix for people struggling to stick to diets, or quit smoking or drinking. Harvard University researcher Robert