Another effect that TikTok has on the brain is an addiction to instant gratification. The short videos train the brain to expect rewards and crave joy obsessively (Coleman, 2023). TikTok utilizes the psychological principle of random reinforcement. In the 1950s, American psychologist and behaviorist B. F. Skinner made an interesting discovery. He found that when rats were given regular pellets as rewards for pressing a lever, they eventually became bored and uninterested in the activity. However, when the pellets were given unpredictably, the rats became obsessive, even abandoning their usual activities (Zaveri, 2023). The dopamine hits that TikTok gives the brain are a very serious problem that causes disordered psychological gratification expectations. In 2019, there was a study published in Nature Communication that suggested that our collective attention span is narrowing due to how quickly people consume content on social media. The Science Times said it was "a relevant study that suggests the app has genuinely affected people's brains” (Coleman, 2023).