Everything you need to know about the Wonder Weeks

Posted in Development.

The Wonder Weeks is a concept created by researchers Frans X. Plooij and Hetty van de Rijt. The husband and wife team used their background in psychology, anthropology and biology to explain the way babies develop, and how parents can support them while they go through big changes. Their work has helped parents better understand what their babies are experiencing and why they behave in a particular way at a specific age.

Ever wondered why your baby goes through very fussy periods?

Your baby’s mental leaps

Plooij and van de Rijt discovered that babies go through profound mental development periods, where they exhibit unsettled behaviour, such as crying, clinginess and interrupted sleep. This would then be followed by what they termed ‘sunny weeks’, where their behaviour would be more placid and content. The researchers suggest there are ten leaps during a child’s first year or two,  with each one encompassing a unique developmental stage. 

Read more about your baby’s development:

What you might notice in your baby

When your baby is going through a Wonder Week, Plooij and van de Rijt say it’s normal for them to be unsettled. According to the researchers, discovering new abilities can be a daunting time, and babies may become frustrated or overwhelmed as they progress through a particular developmental phase. What this translates to is your baby being on the grouchy or irritable side for anywhere between seven days and four weeks – the length of time a wonder week can continue for.

Understanding what’s behind your baby’s clingy behaviour can help you manage it. You can download the Wonder Weeks app to follow your baby’s leaps or just look for cues in their behaviour. For example, separation anxiety can inform you that baby is going through a developmental leap.

What are the leaps (aka stormy periods)?

Babies are busy little people, learning new skills and abilities that build on each other, with children under 20 months experiencing significant neurological changes. These leaps may be physical skills or mental ones, so you won’t always notice what they’re learning.  While all babies are different, and many other factors can influence individual development, Plooij and van de Rijt found that the way babies develop follows a similar path.

On average, these are the leaps (or stormy periods) you can expect your baby to go through during their first two years of life:

Leap 1 – Around 5 weeks:  The world of changing sensations

Your baby is more alert and becomes more sensitive to different sensations.

Leap 2 – Around 8 weeks: The world of patterns

Your baby begins to recognise patterns in the world around him.

Leap 3 – Around 11-12 weeks: The world of smooth transitions

Your baby’s understanding of how his world is organised grows a little more.

Leap 4 – Around 19 weeks: The world of events

Baby learns that experience is split into separate events.

Leap 5 – Around 26 weeks: the world of relationships

Baby begins to understand the relationships between one thing and another in his world.

Leap 6 – Around 37 weeks: The world of categories

Baby gains an understanding of different things belonging in categories.

Leap 7 – Around 46 weeks: the world of sequences

From this age, your baby learns that in order to achieve something, things have to be done in a certain order.

Leap 8 –  Around 55 weeks: the world of programs

Now a toddler, your little person’s way of thinking changes.

Leap 9 – Around 64 weeks: the world of principles

Your toddler becomes more skilful and varied in his behaviour.

Leap 10 – around 75 weeks (17 months): the world of systems

At this age, your toddler is able to modify behaviour according to different systems and circumstances.

How to survive

It’s not easy being a parent to a baby, especially one that is going through big developmental changes. Wonder weeks can be very tiring for mums and dads, so it’s important to take care of yourself along the way, and tend to your own needs for rest (or venting!)

Other tips for surviving your baby’s wonder weeks include:

  • Remember that each fussy period your baby has is just that: a period. It won’t last forever, and if your baby needs extra cuddles and reassurance to get through each leap, then go for it. This will help them feel better quicker!
  • Expect your baby to be clingy and unsettled when a wonder week approaches. These new skills can be scary and overwhelming for them.
  • Don’t worry if your baby or toddler falls out of routine when a leap is occurring. Your baby might want to feed more and sleep may be interrupted, which is all quite normal.
  • Remind yourself that with each leap, your baby is becoming more independent, which is exciting. They won’t need you so intensely as they get older.
  • If it helps to stay at home or spend the day cuddling, then follow your baby’s lead. Wonder weeks are about offering your baby more support and reassurance, which includes keeping things simple.


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