You're trying to make fresh tomato sauce but can't seem to get the tomatoes out of the plastic container.

After a minute of trying, you stop to think. Should you keep pushing and pulling? Should you ask for help? Should you give up on fresh tomatoes and just open a can?

We make decisions like this all the time. How much effort should we expend on something? We have only so much time and energy. Five minutes fumbling with the container is five minutes taken away from reading a book, talking to your family or sleeping. In any situation, you must decide how hard to try.

Developmental cognitive scientists are interested in how we make decisions about effort. In particular, how do young children, who are constantly encountering new situations, decide how hard to try?

IF, AT FIRST, YOU DON'T SUCCEED...

The importance of effort extends beyond daily decisions about time allocation. Studies show that self-control and persistence increase academic outcomes independent of IQ. Our beliefs about effort can affect academic outcomes. Children who think effort leads to achievement outperform those who believe ability is a fixed trait.

Given the link between persistence and academic success, decisions about effort are particularly important in childhood.

We know that infants are keen observers of the social world. But they're not just idly watching. They can generalise abstract concepts like causal relationships and social roles from a few examples. A 15- month-old infant can outperform a high-level computer in such tasks.

Could infants make broad inferences from a few examples when it comes to effort? If so, then maybe "grit" isn't simply a character trait. Maybe it's flexible and adaptable, based on social context.

PUSHING THROUGH FAILURE?

To explore this question, my team and I showed 15-month-old babies one of two things - an experimenter working hard to achieve two different goals (getting a toy out of a box and getting a keychain off a carabiner), or an experimenter who effortlessly reached each goal.

We introduced the baby to a novel "music" toy that looked like it could be activated by pushing a big button on top. (The button could be pressed down but didn't activate anything.)

Out of sight of the babies, we turned on the music toy with a hidden button so that they could hear it making music. We gave them the music toy and left the room.

Coders watched videotapes of the experiment and counted how many times the babies tried to activate the toy by pressing the button.

Across one study and a preregistered replication (182 babies in total), babies who had seen an adult persist and succeed, pushed the button about twice as many times as those who saw an adult effortlessly succeed. In other words, babies learnt that effort was valuable after watching just two examples of an adult working hard and succeeding.

Part of what's exciting about this finding is that the babies didn't just imitate the adult's actions. Instead, they generalised the value of effort to a novel task. The experimenter never demonstrated pushing a button or trying to make music. Instead, the babies learnt from different examples of effortful actions (opening a container or unlatching a carabiner) that the new toy probably also required persistence.

However, most of the time when a parent is frustrated, he's focused on the task at hand and not on trying to teach his child the value of effort. Can babies learn the value of effort from adults who are not deliberately demonstrating to them?

We ran the experiment again, eliminating cues such as eye contact or child-friendly speech.

Again, the infants tried harder on their own task after seeing an adult persist and succeed. But the effects were much weaker when the adult didn't use any pedagogical cues.

LEARNING TENACITY BY WATCHING

Educators and parents want to know how to foster persistence when children encounter challenges. Our study suggests that persistence can be learnt from adult models. Babies watch those around them and use that information to guide their own behaviour.

Yet babies don't simply learn they should try harder at everything. Like adults, they make rational decisions about effort. If they see someone trying hard and succeeding, they try harder. When they see someone succeed effortlessly, they infer that effort may not be worthwhile.

So what does this mean? We can't presume that our results would work for parents at home as in the laboratory. If you know your baby can achieve a task if she tries hard, it might be worth modelling effort and success for her first.

This study suggests that parents don't have to make things look easy all the time.

The next time you struggle to open that tomato container, it's okay, maybe even beneficial, to let your child see you sweat.

• The writer is a PhD student in brain and cognitive sciences at Massachusetts Institute of Technology .

• This article first appeared in The Conversation at http://theconversation.com, a website which carries analysis by academics and researchers .