The verbs hear, see, notice and watch can be followed by object + infinitive without to or object + -ing form.
- I heard him go down the stairs.
- I watched him cross the road.
- I saw her light the lamp.
- We heard her scream.
- I watched them play in the garden.
There is a difference between the infinitive and the –ing form. The infinitive suggests that we see or hear the whole of an action or event. An –ing form, on the other hand, suggests that we hear or see an action in progress.
A progressive form can suggest repetition.
- I saw her throwing stones at the dog.
Only –ing forms can be used after can see, can hear, can smell etc.
- I could smell something burning.
- I could hear her crying.
We cannot use possessive forms with –ing forms after these verbs.
- I saw Mary lighting the lamp. (NOT I saw Mary’s lighting the lamp.)
Look at can be followed by an object + -ing form. In American English, object + infinitive is also possible.
- Look at him eating!
- Look at him eat!