Social & Emotional
Reacts when you leave
Typical Timing & Development Window
Starts
28
wk avg
Median
40
wk
Std dev
±4
wk
Flag
48
wk
Visual Timeline & Milestone Benchmarks
Typical range (68% of babies)
Earliest typical start
Median milestone age
Pediatrician check-in flag
What these numbers mean
Starts
~wk 28
The average age babies first begin showing early signs of this skill. Before this, it's simply too early — there's nothing to worry about.
Median
wk 40
The midpoint age: half of babies have reached this milestone by here, half a little later. It's a typical target, not a deadline.
Std dev
±4 wk
How spread out the timing is. About two-thirds of babies achieve it within one standard deviation of the median (the shaded band, wk 36–44). Wide bands mean a normal range of variation.
Flag
wk 48
A gentle check-in point. If your baby hasn't shown this by around here, it can be worth mentioning to your pediatrician — most often it's still perfectly fine, just later.
About this milestone
The infant shows distress or separation protest when a caregiver departs, reflecting attachment development.
What to try & how to support
- 1. Keep goodbyes brief and predictable, and provide soothing on reunions to reassure safety.
What to avoid & gentle reminders
- 1. Avoid sneaking away unexpectedly; predictable routines reduce prolonged distress.