On January 19, as TikTok was completely shut down in the United States, 170 million American users officially became "TikTok refugees." However, its resurrection after a brief shutdown indicates that this saga is far from over. Amid the wails across the internet, people lament that their lives have long been inseparable from TikTok. Since its inception, TikTok has captivated countless netizens with its precise short-video algorithm, drawing them into an endless cycle of scrolling and refreshing the app obsessively.

As short videos continue to consume our attention and time, have you ever wondered what is really happening to our brains behind this addiction?

1. Why Is It Addictive? 

A recent functional magnetic resonance imaging (fMRI) study has revealed the connection between short videos and addiction (as shown in the figure) [3]. The study conducted a survey of 153 Douyin users, finding that approximately 45.8% of participants exhibited mild to moderate addiction to the platform, while 5.9% were severely addicted. Statistical analysis showed that the lower a person's self-control, the higher their level of addiction. Common modern anxieties may drive people to view short videos as a refuge from stress, and those with poor self-control may find it even harder to break free from this escapism, leading to an excessive dependence on short video content.

Adolescent addiction to short videos is a major concern. Hormonal changes caused by brain development can affect teenagers' self-control and expose them to higher mental health risks. This may make them more susceptible to short-video addiction, which in turn can negatively impact their mental well-being.  

A 2021 study surveying over 3,000 teenagers found that those who were overly reliant on Douyin were more likely to experience psychological issues such as depression and anxiety, which could lead to a decline in short-term memory. Excessive smartphone use also tends to lower sleep quality among teenagers, affecting healthy brain development.  

Moreover, short-video content can influence teenagers’ self-perception. Among female participants, the frequency of using Douyin and other social media platforms was positively correlated with appearance-related anxiety. Short videos may also reinforce upward social comparisons*, reducing teenagers' self-confidence and self-esteem.

Furthermore, short videos have become a new source of emotional support for middle-aged and elderly individuals after retirement. Their relatively limited social interactions allow them to devote significant amounts of time to short-video platforms. Additionally, due to their lack of experience with internet recommendation algorithms, they may be more easily immersed and addicted to such content.  

As people age, cognitive decline can weaken self-control, and the need for social recognition may further contribute to short-video addiction. Although the effects of short videos on the aging brain remain unclear, one thing is certain: maintaining brain health requires regular physical exercise and an active social life. The habit of endlessly scrolling through short videos may replace these healthier routines, potentially having a negative impact on cognitive aging.

2. The Brain in a State of Immersion

A decrease in （default mode network (DMN)） activity is the most noticeable signal that the brain is focusing its attention. The DMN is a large neural network spanning the brain, primarily composed of the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus. It becomes highly active when a person is idle or lost in thought. Additionally, it plays a role in various complex cognitive functions, including environmental observation, self-referential processing, and social cognition.  

Self-referential processing refers to the cognitive process of thinking about information related to oneself, such as recalling past experiences, planning for the future, and reflecting on the present. In short videos, personalized recommendations often closely align with users' preferences, interests, and experiences, triggering their self-referential thinking process.  

During this process, the medial temporal subsystem, responsible for projecting past and future events, becomes less active, while the dorsomedial prefrontal cortex subsystem, which processes present-moment awareness, becomes more active. As a result, thoughts about the past and future are suppressed, and attention is entirely focused on the present.  

At the same time, communication between the DMN and the primary visual cortex, primary auditory cortex, and frontoparietal network is enhanced. The primary sensory cortices decode and process fundamental visual and auditory stimuli, while the frontoparietal network is responsible for maintaining attention and short-term memory. The close collaboration of these networks evokes past positive viewing experiences, which in turn top-down regulate attention allocation, making users focus more on the visual and auditory stimuli provided by the video.

3. Focused Attention

The posterior cingulate cortex (PCC) is a crucial hub of the default mode network (DMN) and plays a key role in balancing internally oriented attention (focused on internal thoughts) and externally oriented attention (focused on external stimuli). Short-video recommendations strengthen the connection between the PCC and the superior frontal gyrus and middle frontal gyrus, which are responsible for short-term memory. This shift redirects the viewer's attention from external stimuli to internal processing. By integrating video information stored in short-term memory, the brain engages in deeper, more meaningful, and higher-level processing of the video content.

While certain brain regions become more active, others show a decrease in activity. The dorsal anterior cingulate cortex, caudate nucleus, and parts of the thalamus are responsible for attention allocation and inhibition control. When watching short videos, activity in these areas diminishes, signaling a reduction in self-control. Additionally, weakened connections between these regions and the DMN further impair individuals’ ability to regulate self-control and maintain conscious awareness. As a result, people become deeply immersed in short-video consumption, making it difficult to disengage.

4. Addiction and Compulsion

When watching videos, the brain’s reward pathway is activated by the stimuli. Neurons in this pathway release large amounts of dopamine, reinforcing the association between certain behaviors and pleasure, thereby creating a strong desire to repeat those behaviors.

A 2019 study revealed that the cerebellum might also be part of the reward pathway, as it is directly connected to the ventral tegmental area (VTA)—one of the brain's core regions for processing rewards . The VTA, along with the substantia nigra, strengthens behaviors that lead to rewards. The substantia nigra encodes the salience of information, making certain stimuli stand out from background noise, while the VTA neurons assess the value of rewards. This process allows the brain to prioritize sensory information from videos, making these stimuli seem especially valuable.

Studies have found that compared to regular videos, algorithm-recommended personalized videos significantly activate the VTA, indicating that these recommended videos have a higher reward value for viewers, making them more addictive.

5. Does This Affect Cognitive Abilities?

Since the rise of short videos is a relatively recent phenomenon, there is currently insufficient evidence to determine their exact effects on human cognitive abilities. However, many scientists have begun researching how information technology might be altering the human brain, and the academic community has produced several studies that may offer insights and hypotheses for further investigation.

Some studies have found that short bursts of fast, immediate information intake on the internet can make it harder for people to maintain long-term attention. A 2020 study published in Nature on "social networks use disorder" found that the level of social media addiction is positively correlated with attentional impulsivity. Moreover, the study suggested a bidirectional relationship—people prone to impulsive attention shifts are also more easily drawn to social media. The research team speculated that online stimuli may weaken self-control by affecting the brain's attention processes, leading people to pursue instant rewards while ignoring long-term risks. As a result, individuals are more easily drawn to social media notifications and visual stimuli, heightening their craving for rewards and making it harder to resist impulses .

A review published in World Psychiatry also highlighted how "information rewards" on the internet reinforce compulsive phone-checking behavior by stimulating the cortico-striatal dopaminergic system . One brain imaging study mentioned in the review found that people who frequently multitask perform worse on distraction tasks, despite increased activity in related brain regions . This suggests that the brain is working harder but achieving worse results, indicating inefficiency.

Additionally, a study on brain structure found that heavy internet users exhibited reduced gray matter volume in the prefrontal cortex, specifically in areas responsible for resisting distractions and maintaining task focus. Since gray matter is a key neural tissue composed of densely packed neurons, this finding hints at potential damage to brain health from excessive internet use. However, this research is still in its early stages, and further replication studies are needed to confirm these findings .

While many studies point to the negative effects of excessive internet use, there is still no conclusive evidence proving that any resulting cognitive decline is long-term or irreversible. Therefore, as long as we manage our screen time wisely and balance online entertainment with real-life interactions—such as chatting over tea with family and friends—we can still enjoy the best of both worlds.