She can't talk. She just sits there gurgling, if you're lucky. Or screaming, if you're not. But now scientists have found there might be far more going on behind the unfocused eyes of a baby girl than just "I'm tired" or "Feed me. Now!"
New studies suggest that the very young are capable of surprisingly adult emotions such as jealousy or even empathy.
Science has got used to thinking of the emotional life of a baby as a "great, blooming, buzzing confusion". But now a series of ground-breaking studies carried out by American psychologists has overturned conventional notions of what a baby understands and feels. According to the findings, babies as young as four months are highly sophisticated, both intellectually and emotionally.
The studies could even lead to doctors spotting disorders such as autism, depression and learning difficulties at a far earlier stage than ever before. By detecting symptoms sooner, doctors may be able to help children to cope with these disorders more effectively.
While much of the new research has relied on traditional methods of observing babies' behaviour, such as body language and facial reactions, scientists are increasingly turning to brain scans.
Professor Robert Winston, whose BBC series Child of our Time explores the behavioural patterns of a group of children as they grow up, said neuroscience could be the key to discovering how a baby's brain operates. "Neuroscience is now a very important research area in biology. We are now understanding a lot more about brains in babies, as well as children and adults," Professor Winston said.
The findings, which are revealed in the influential American news magazine Newsweek, could enable child psychologists to develop emotional milestones which babies should be expected to reach by certain ages, in a similar way to the physical milestones such as crawling, walking and talking.
One of the key studies has been conducted by Professor Charles Nelson, a Harvard neuroscientist, who has devised a programme that attempts to measure brainwave activity within a baby's head. A cap wired with 64 sensors is placed on the head of the infant, who is then shown a series of 60 different photographs of a woman. Each picture features a different facial expression; a computer attached to the sensors monitors the baby's reactions.
Professor Nelson hopes to find out whether babies can classify different emotions in the same way an adult can, although the results will not be known until later this year. Scientists are hoping to take this work one step further by developing MRI scans that will enable researchers to delve even further into a baby's brain.
Proof that babies younger than six months can understand different facial expressions is provided by Dr Diane Montague at La Salle University in Philadelphia. Experiments based on playing peekaboo suggested that babies reacted differently to happy, sad and angry faces. "Most textbooks still say that babies younger than six months do not recognise emotions," Dr Montague said. But her experiments in Philadelphia demonstrate otherwise. "It shows that babies younger than six months find meaning in expressions."
This, scientists claim, supports research which suggests that babies can feel empathy. Babies who have been played tape recordings of other young children crying do not take long to start shedding tears themselves. But when the same infants are played recordings of their own bawls and screams, the tears dry up.
Professor Martin Hoffman, a psychologist at New York University and an expert on social and emotional development, including empathy, said that while it has always been known that babies cry when they hear other infants doing likewise, no one has truly understood why. This new research, Professor Hoffman said, proves that "rudimentary empathy is in place right from birth".
But it is not just positive feelings such as empathy which babies appear to develop at an early age. Studies carried out at Texas University have shown that babies can also experience jealousy. In the experiment, a mother and daughter are filmed playing together. Then the mother is handed a baby doll and is instructed to give all her attention to the doll rather than her child. On almost every occasion, the child gets upset and starts crying.
Other studies analysing babies' awareness, shyness and even their ability to learn foreign languages have increased child psychologists' and paediatricians' knowledge of what goes on inside a baby's brain. Most importantly for parents, these advances will enable scientists to establish developmental markers throughout a child's early years.
Using the fusiform gyrus, babies are able to tell the difference between strangers and carers. It develops at four months and is key to building trust
The angular gyrus enables babies to understand the basic sounds of languages.
The peak level of connections
between nerve cells is at eight months, before it falls towards the lower level of adults by the age of four
The dorsolateral prefrontal cortex can help infants remember images and faces. When parents break up, babies as young as eight months old can suffer anxiety from missing a parent
Seeing & hearing
The visual and auditory cortices are two of the first areas to fully develop. They tend to reach their peak after just three months
One of the most crucial parts of the brain. The hippocampus drives a baby's memory. By the age of five years, it should be well developed
The prefrontal cortex is involved in emotional control. One of the slowest areas to develop, it peaks at the age of one year
What your baby can do
Every parent thinks their little darling is special, but how is he or she really doing? Psychologists have devised these emotional milestones. If you do not have a baby, try them out on your partner
Expect the baby to take a keen interest in those around them and respond to different sounds and facial expressions. Most child psychologists agree that emotions at such an early age are limited to happy, sad and angry.
Babies will begin to express emotions like joy and surprise. They should seem happy when he or she sees familiar faces. The new research suggests that babies will have already mastered jealousy and empathy by this stage.
Babies will begin to learn to follow their parents' gazes to understand what they are interested in. They will have a better understanding of how to get attention by trying to catch a parent's eye. Parents are encouraged to repeat sounds and faces that the baby makes.
Toddlers experience more complicated emotions as they become more self-aware. Children will increasingly turn to their parents for assistance in trying to solve problems, something that will help them learn to play with others in their age group. Parents can help this process by creating a problem which they can solve together with the child.
Additional research by Graham MoonieReuse content