Scientists have built a robot baby to reveal how bubs kick up clouds of "biogunk" when they crawl across carpets.
A new US study created robot babies to reveal how bubs' movement across floors, especially carpeted surfaces, stirred up high levels of dirt, skin cells, bacteria, pollen, and fungal spores.
In the process, the infants inhaled a dose of "biogunk" in their lungs that was four times what an adult would breathe walking across the same floor.
But as alarming as that sounded, lead researcher Dr Brandon Boor, of Purdue University, was quick to add that wasn't necessarily a problem.
"We are interested in the biological material an infant inhales, especially during their first year of life when they are crawling," Boor said.,
"Many studies have shown that inhalation exposure to microbes and allergen-carrying particles in that portion of life plays a significant role in both the development of, and protection from, asthma and allergic diseases.
"There are studies that have shown that being exposed to a high diversity and concentration of biological materials may reduce the prevalence of asthma and allergies later in life."
Scientists have previously carried out studies to determine how much dirt and biological material is kicked up and resuspended into the air when an adult walks indoors, but this was the first to look at what happened with infants and their unique forms of locomotion.
Human babies were the only mammals that couldn't get up and walk soon after being born.
Elephants, giraffes, horses, all could take a few wobbly steps soon after they entered the world, but it was months before a human could claim the same accomplishment.
As babies rolled, slid and crawled on the floor, their movements stirred up more particulates into the air, and their mouths and nostrils were much closer to the floor where the concentrations were greater.
This was countered somewhat by the fact that babies tended to move in much shorter bursts of activity than older children or adults.
To study just how much of the floor debris babies breathe, the research team built a robotic crawling baby and tested it crawling on actual carpet samples they had removed from homes.
Then the researchers measured and analysed the breathing zone to find a concentrated cloud of re-suspended particles formed around them.
These could be as much as 20 times greater than the levels of material higher in the room.
Moreover, infants' bodies weren't as good at blocking this dust storm, Boor said.
"For an adult, a significant portion of the biological particles are removed in the upper respiratory system, in the nostrils and throat.
"But for very young children, they more often breathe through their mouths, and a significant fraction is deposited in the lower airways - the tracheobronchial and pulmonary regions.
"The particles make it to the deepest regions of their lungs."
Counter-intuitively, perhaps, this may be just what nature intended.
In the late 1980s, British epidemiologist David Strachan was the first to propose the
"hygiene hypothesis", which suggested that too clean of an environment may suppress the development of the immune system.
Allergists also sometimes refer to this as "the farming effect".
"Exposure to certain bacterial and fungal species can result in the development of asthma, but numerous studies have shown that when an infant is exposed to a very high diversity of microbes, at a high concentration, they can have a lower rate of asthma later in life," Boor said.
"Such exposures act to stimulate and challenge your immune system."
Do video games really make us more violent?
It's often been said playing violent video games, in turn, makes the player more violent in real life.
But UK researchers who carried out an exhaustive study, involving more than 3000 participants, have found no evidence to support that theory.
The University of York team demonstrated video game concepts didn't "prime" players to behave in certain ways - and that increasing the realism of violent video games also didn't not necessarily make them more aggressive.
The dominant model of learning in games is built on the idea that exposing players to concepts, such as violence in a game, makes those concepts easier to use in reality.
Called "priming", this is thought to lead to changes in behaviour, although previous experiments on the effect have yielded mixed conclusions.
The researchers expanded the number of participants in experiments, compared to studies that had gone before it, and compared different types of gaming realism to explore whether more conclusive evidence could be found.
In one study, participants played a game where they had to either be a car avoiding collisions with trucks or a mouse avoiding being caught by a cat.
Following the game, the players were shown various images, such as a bus or a dog, and asked to label them as either a vehicle or an animal.
"If players are 'primed' through immersing themselves in the concepts of the game, they should be able to categorise the objects associated with this game more quickly in the real world once the game had concluded," study author Dr David Zendle said.
"Across the two games we didn't find this to be the case."
Participants who played a car-themed game were no quicker at categorising vehicle images, and indeed, in some cases, their reaction time was significantly slower.
In a separate, but connected study, the team investigated whether realism influenced the aggression of game players.
Research in the past has suggested that the greater the realism of the game, the more primed players are by violent concepts, leading to anti-social effects in the real world.
"There are several experiments looking at graphic realism in video games, but they have returned mixed results," Zendle said.
But there were other ways that violent games could be realistic, such as the way their characters behaved.
"Our experiment looked at the use of 'ragdoll physics' in game design, which creates characters that move and react in the same way that they would in real life."
Human characters were modelled on the movement of the human skeleton, and how that skeleton would fall if it was injured.
The experiment compared player reactions to two combat games, one that used "ragdoll physics" to create realistic character behaviour and one that did not, in an animated world that nevertheless looked real.
Following the game the players were asked to complete word puzzles called word fragment completion tasks, where researchers expected more violent word associations would be chosen for those who played the game that employed more realistic behaviours.
They compared the results of this experiment with another test of game realism, where a single bespoke war game was modified to form two different games.
In one of these games, enemy characters used realistic soldier behaviours, whilst in the other game they did not employ realistic soldier behaviour.
"We found that the priming of violent concepts, as measured by how many violent concepts appeared in the word fragment completion task, was not detectable," Zendle said.
"The findings suggest that there is no link between these kinds of realism in games and the kind of effects that video games are commonly thought to have on their players."