Parents dutifully record their children’s developmental breakthroughs in baby books, documenting their first laugh, first steps, and first words—but what about their first lie? It might be worth jotting down beside the other milestones. New research published in the journal Cognitive Development shows kids learn to lie early, adding new types of deception to their repertoire as their tiny conniving minds develop.
An international team of psychologists led by Elena Hoicka of the University of Bristol asked parents of more than 750 children up to 47 months old to complete an online survey about their kids’ deceptive behaviors. After analyzing the results, they identified 16 distinct types of deception—from withholding information, to exaggerating, to outright fabrication.
They found that around a quarter of children deployed deception before they reach 10 months old (with the earliest report around 8 months), and half by 17 months. Once kids started lying, they kept at it, too, with half the parents of little liars reporting their child had attempted to deceive them in the past 24 hours alone. By the time they reach their third birthdays, most kids are master manipulators, researchers found.
“It was fascinating to uncover how children’s understanding and usage of deception evolves from a surprisingly young age and builds in their first years so they become quite adept and cunning ‘little liars,’” Hoicka explained in a statement. “As a mother of three children myself, I can certainly vouch for how artful and wily they can be. Hiding under the table or in the bathroom to eat sweets or chocolate is their common ploy.”
Read more: “The Strange Physics of How Babies Talk”
According to the results, different types of deception were more likely to emerge at different ages, which researchers say reflects the development of their cognitive and linguistic aptitudes.
“From two years, deception tends to be action-based, or require only basic spoken responses, liked pretending not to hear their parent say ‘time to tidy up,’ hiding things from others, or denial—such as eating chocolate but shaking head to say ‘no’ when asked if they ate chocolate,” Hoicka said.
After three years of age, kids branch out into lying that requires more advanced representational thought, better working memory, and more developed linguistic skills.
“This could mean exaggerating, such as saying ‘I ate all my peas’ when they only ate a quarter, understatement, or indeed complete fabrication such as telling a lie like ‘a ghost ate the chocolate,’ as well as pretending not to know, see, or understand,” Hoicka continued. “They also start to withhold information, for instance accurately telling their parents their sibling hit them, while leaving out the fact that they hit their sibling first.”
Lying, the researchers stress, is completely normal for kids, and they hope these findings will give parents, educators, and caretakers a road map of what to expect as children develop.
So the next time your toddler tries to pull a fast one, consult the research. It might just be cause for celebration that they’re lying at an advanced level. 
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Lead image: Bogdan Sonjachnyj / Shutterstock
