High amounts of screen time begin as early as infancy

Child using tablet device

Children's average daily time spent watching television or using a computer or mobile device increased from 53 minutes at age 12 months to more than 150 minutes at 3 years, according to an analysis by researchers at the National Institutes of Health, the University at Albany and the New York University Langone Medical Center. By age 8, children were more likely to log the highest amount of screen time if they had been in home-based childcare or were born to first-time mothers. The study appears in JAMA Pediatrics.

"Our results indicate that screen habits begin early," said Edwina Yeung, Ph.D., the study's senior author and an investigator in the Epidemiology Branch of NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). "This finding suggests that interventions to reduce screen time could have a better chance of success if introduced early."

NICHD researchers and their colleagues analyzed data from the Upstate KIDS Study, originally undertaken to follow the development of children conceived after infertility treatments and born in New York State from 2008 to 2010. Mothers of nearly 4,000 children who took part in the study responded to questions on their kids' media habits when they were 12, 18, 24, 30, and 36 months of age. They also responded to similar questions when the children were 7 and 8 years old. The study compiled additional demographic information on the mothers and children from birth records and other surveys.

The American Academy of Pediatrics recommends avoiding digital media exposure for children under 18 months of age, introducing children 18 to 24 months of age to screen media slowly, and limiting screen time to an hour a day for children from 2 to 5 years of age. In the current study, researchers found that 87% of the children had screen time exceeding these recommendations. However, while screen time increased throughout toddlerhood, by age 7 and 8, screen time fell to under 1.5 hours per day. The researchers believe this decrease relates to time consumed by school-related activities.

The study authors classified the children into two groups based on how much their average daily screen time increased from age 1 to age 3. The first group, 73% of the total, had the lowest increase, from an average of nearly 51 minutes a day to nearly an hour and 47 minutes a day. The second group, 27% of the total, had the highest increase, from nearly 37 minutes of screen time a day to about 4 hours a day. Higher levels of parental education were associated with lower odds of inclusion in the second group. In addition, girls were slightly less likely to be in the second group, compared to boys, while children of first-time mothers were more likely to be in the high-increase group.

The researchers also classified the children into percentiles based on their total daily screen time. Children were more likely to be in the 10th, or highest, percentile if their parents had only a high school diploma or equivalent (more than twice as likely) or were children of first-time mothers (almost twice as likely). Similarly, compared to single-born children, twins were more likely to belong to the highest screen time group. Compared to children in center-based care, children in home-based care, whether provided by a parent, babysitter or relative, were more than twice as likely to have high screen time.

What keeps cells in shape? New research points to two types of motion

Illustration of human cell 

The health of cells is maintained, in part, by two types of movement of their nucleoli, a team of scientists has found. This dual motion within surrounding fluid, it reports, adds to our understanding of what contributes to healthy cellular function and points to how its disruption could affect human health.

"Nucleolar malfunction can lead to disease, including cancer," explains Alexandra Zidovska, an assistant professor in New York University's Department of Physics and the senior author of the study, which appears in the journal eLife. "Thus, understanding the processes responsible for the maintenance of nucleolar shape and motion might help in the creation of new diagnostics and therapies for certain human afflictions."

Recent discoveries have shown that some cellular compartments don't have membranes, which were previously seen as necessary to hold a cell together. Researchers have since sought to understand the forces that maintain the integrity of these building blocks of life absent these membranes.

What has been observed is the nature of this behavior. Specifically, these compartments act as liquid droplets made of a material that does not mix with the fluid around them -- similar to oil and water. This process, known as liquid-liquid phase separation, has now been established as one of the key cellular organizing principles.

In their study, the researchers focused on the best known example of such cellular liquid droplet: the nucleolus, which resides inside the cell nucleus and is vital to cell's protein synthesis.

"While the liquid-like nature of the nucleolus has been studied before, its relationship with the surrounding liquid is not known," explains Zidovska, who co-authored the study with Christina Caragine, an NYU doctoral student, and Shannon Haley, an undergraduate in NYU's College of Arts and Science at the time of the work and now a doctoral student at the University of California at Berkeley. "This relationship is particularly intriguing considering the surrounding liquid -- the nucleoplasm -- contains the entire human genome."

Yet, unclear is how the two fluids interact with each other.

To better understand this dynamic, the scientists examined the motion and fusion of human nucleoli in live human cells, while monitoring their shape, size, and smoothness of their surface. The method for studying the fusion of the nucleolar droplets was created by the team in 2018 and reported in the journal Physical Review Letters.

Their latest study showed two types of nucleolar pair movements or "dances": an unexpected correlated motion prior to their fusion and separate independent motion. Moreover, they found that the smoothness of the nucleolar interface is susceptible to both changes in gene expression and the packing state of the genome, which surrounds the nucleoli.

"Nucleolus, the biggest droplet found inside the cell nucleus, serves a very important role in human aging, stress response, and general protein synthesis while existing in this special state," observes Zidovska. "Because nucleoli are surrounded by fluid that contains our genome, their movement stirs genes around them. Consequently, because the genome in the surrounding fluid and nucleoli exist in a sensitive balance, a change in one can influence the other. Disrupting this state can potentially lead to disease."

How does language emerge?

The word 'welcome' in different languages 

How did the almost 6000 languages of the world come into being? Researchers from the Leipzig Research Centre for Early Childhood Development at Leipzig University and the Max Planck Institute for Evolutionary Anthropology have tried to simulate the process of developing a new communication system in an experiment -- with surprising results: even preschool children can spontaneously develop communication systems that exhibit core properties of natural language.

How the languages of the world emerged is largely a mystery. Considering that it might have taken millennia, it is intriguing to see how deaf people can create novel sign languages spontaneously. Observations have shown that when deaf strangers are brought together in a community, they come up with their own sign language in a considerably short amount of time. The most famous example of this is Nicaraguan Sign Language, which emerged in the 1980s. Interestingly, children played an important role in the development of these novel languages. However, how exactly this happened has not been documented, as Manuel Bohn describes: "We know relatively little about how social interaction becomes language. This is where our new study comes in."

In a series of studies, researchers at the Leipzig Research Centre for Early Childhood Development and the Max Planck Institute for Evolutionary Anthropology attempted to recreate exactly this process. The idea had been around for quite some time, says Gregor Kachel. But there was a problem: how to make children communicate with each other without them reverting to talking to each other? The solution came up in Skype conversations between the two researchers from Germany and their colleague Michael Tomasello in the US. In the study, children were invited to stay in two different rooms and a Skype connection was established between them. After a brief familiarization with the set-up, the researchers sneakily turned off the sound and watched as the children found new ways of communicating that go beyond spoken language.

The children's task was to describe an image with different motifs in a coordination game. With concrete things -- like a hammer or a fork -- children quickly found a solution by imitating the corresponding action (e.g. eating) in a gesture. But the researchers repeatedly challenged the children with new, more abstract pictures. For example, they introduced a white sheet of paper as a picture. The depicted "nothing" is difficult to imitate. Kachel describes how two children nevertheless mastered this task: "The sender first tried all sorts of different gestures, but her partner let her know that she did not know what was meant. Suddenly our sender pulled her T-shirt to the side and pointed to a white dot on her coloured T-shirt. The two had a real breakthrough: of course! White! Like the white paper! Later, when the roles were switched, the recipient didn't have a white spot on her T-shirt, but she nevertheless took the same approach: she pulled her T-shirt to the side and pointed to it. Immediately her partner knew what to do." Within a very short time, the two had established a sign for an abstract concept. In the course of the study, the images to be depicted became more and more complex, which was also reflected in the gestures that the children produced. In order to communicate, for example, an interaction between two animals, children invented separate gestures for actors and actions and began to combine them -- thus creating a kind of small local grammar.

How does a language emerge? Based on the present study, the following steps appear plausible: first, people create reference to actions and objects via signs that resemble things. The prerequisite for this is a common ground of experience between interaction partners. Partners also coordinate by imitating each other such that they use the same signs for the same things. The signs thus gain interpersonal and eventually conventional meaning. Over time, the relationships between the signs and things become more abstract and the meaning of the individual signs more specific. Grammatical structures are gradually introduced when there is a need to communicate more complex facts. However, the most remarkable aspect of the current studies is that these processes can be observed under controlled circumstances and within 30 minutes.

The studies demonstrate that communication cannot be reduced to words alone. When there is no way to use conventional spoken language, people find other ways to get their message across. This phenomenon forms the basis for the development of new languages. The study by Manuel Bohn, Gregor Kachel and Michael Tomasello shows what the first steps in the development of a new language could look like. According to Bohn, however, numerous new questions arise at this point: "It would be very interesting to see how the newly invented communication systems change over time, for example when they are passed on to new 'generations' of users. There is evidence that language becomes more systematic when passed on."