Your toddler is starting to use some negative phrases themselves now (or will be soon), so it isn’t unreasonable to think they can understand negatives. While they do, in theory, understand negative instructions and phrases, in practice this approach to giving instructions or making requests might cause confusion.
Your toddler is still developing the ability to control their attention
When your toddler is busy, or you are in noisy or exciting place, they might find it difficult to really focus on what you’re saying so might pick out just a few keywords.
If you say, “Don’t run up the slope.” or, “No jumping on the sofa” they might focus on ‘run’ and ‘slope’ or ‘jumping’ and ‘sofa’.
Try to avoid giving your toddler ideas (even if your intention is to tell them what not to do!)
You might think, I’ll prepare my toddler before we go to the restaurant with the family by telling them the things they shouldn’t do. “No running around during the meal and don’t ask Uncle to share his food.”
Your toddler might not have been thinking about running or sharing food – but they probably will be once you have told them what not to do.
Instead, turn the negatives into positives
Think about how you turn your instructions or requests into positives which will ensure your toddler understands straight away – and won’t prime them to do precisely the thing you’d rather they didn’t.
“Let’s walk down the slope.”
“Jump on the floor now”, “Let’s go outside and jump together” or even, “Jumping's finished now.”
“We’ll sit down at the table.”
“We’re all going to eat our own food – I wonder what you’ll have?”
Most of us are quite used to instructions and requests being given as negative statements – so this switch might take a bit of practice!