Have you ever heard someone describe your baby or someone else's as being a "really happy baby"?
It's a phrase people often use, but what do they mean when they describe a baby as happy? One that doesn't cry (if such a thing exists)? Or just one who smiles a lot?
Jeni Hooper is a Child Psychologist and Wellbeing Coach, specialising in positive psychology. She agreed that yes, there is such a thing.
"We can look at baby happiness as having two aspects: the personal and the social side," Hooper tells HuffPost UK Parents.
"A baby’s personal needs are for food, warmth, adequate sleep, being kept clean and comfortable, and protection from harm.
"An equally importantly personal need is for a stimulating environment that starts the process of learning and brain growth.
"Sights, sounds, touch and taste all spark the brain cells to grow and begin to connect up, so your baby begins to recognise the world around them."
And, as Hooper explains, babies have social needs too that lead to happiness. They are born with a capacity to love and seek to connect with their parents and family.
"Oxytocin is released when a baby is held and touched, which creates calm and contentment. A happy baby is cared for and loved," she adds.
But a baby's smile isn't always the indicator of a happy baby. Hooper explains that a baby's first smile is a reflex smile, testing out muscles and getting them ready to talk.
These early reflex smiles have no meaning, but from around six to eight weeks, they develop the ability to smile intentionally.
"These smiles allow your baby to tell you how great it is to see you or to ask you repeat something that was fun," Hooper explains.
When parents, family members and friends alike refer to babies as being a 'happy', Hooper says it is defining them as being calm, content and easily soothed as their needs have been met, rather than a comment on the baby's personality.
"That's much more due to how sensitively needs are being met," she tells HuffPost UK Parents.
"A baby is totally dependent on how well parents understand what is being communicated.
"Babies are also very social beings, biologically primed to seek and maintain closeness, that’s why often a baby stops crying when picked up and starts again if put down again too soon."
"Every baby will be happy if they are healthy, free from pain and discomfort, well cared for and loved."
Hooper adds some parents might become worried their baby is distressed if they see other babies looking calm more often. There are things you can do to increase your baby's happiness, but it's important to remember that all baby's are individuals.
Although some babies might seem to be happier and calmer than others, it is biological temperament that determines both their liveliness and how quickly they are soothed by their parents' attention.
When they begin to grow and develop personalities, you can work out what things they prefer doing. Is it going outside? Or do they love playing with colourful toys?
Here are Hooper's tips for ensuring your baby is as happy as can be:
Always check your baby is well and comfortable.
Discomfort will affect how calm and content a baby seems to be. Although babies are physically helpless they have a remarkable ability to communicate. Every baby is an individual who wants us to know what they need.
Notice what works for your baby, but don’t get too caught up with trying to follow a parenting system.
These systems can be very different from each other, from attachment parenting at one end of the spectrum, which focuses on having your baby close by and instantly responding to your child. While a very different approach advises parents to train your baby to your routine and not to respond to every cry.
Advice to parents is there to help you, not to override your experience and intuition as you get to know your baby."
Aim for a balance which meets your baby’s needs for both care and stimulation.
Look after yourself too and seek help from family and friends so you get a chance to rest and be refreshed. A tired parent is less able to tune into baby and more likely to become anxious or unhappy.
Babies need to play to explore the world and learn about their environment.
It works better and is more fun when an adult is involved to bring new experiences. Tiny babies love big, bold and bright objects as their vision is developing and confined to close range.
Work with your baby's alertness and curiosity, see it as like holding a conversation where you adjust to the response you get.
Focusing on wellbeing and positive psychology, Hooper says that when your baby starts to grow in their first year there are things you can do to ensure their wellbeing.
"The baby and toddler years see rapid brain development which makes learning new skills possible such as walking and talking," she explains.
"A newborn baby’s brain has all the brain cells there waiting for experience and stimulation to join them together into a working, thinking brain with a remarkable capacity for learning.
"Work with what your baby is telling you and things will go brilliantly."
If you want to share your stories about what makes your children happy, share your photos with us on Instagram with the hashtag #HPhappy