Hear, see, etc. + object + infinitive or -ing

We can use either the infinitive without to or the -ing form after the object of verbs such as hear, see, notice, watch. The infinitive without to often emphasizes an action or event which is in progress or not yet completed.

Compare

He saw her drive off with a young man in the passenger seat. 

-> The speaker observed the whole event. 

Maria heard him coming up the stairs towards her room, and felt scared. 

-> The action was in progress, happening, but not completed. 

The -ing form can also emphasize that an action or event is repeated: 

We watched them running back and forth, loading and unloading the trucks and taking boxes in and out of the building. 

After can or could with one of these verbs, we always use the -ing form, not the infinitive:

I can hear people talking. They must be in the next room.

Not: I can hear people to talk. 

Typical errors 

• We don't use to with the infinitive form after the object:

She heard the doorbell ring and went to answer it. 

Not: She heard the doorbell to ring ...

• We don't use a finite verb form after the object: 

I watched the woman come out of the house and get into a car. 

Not: I watched the woman came out of the house and got into a car. 

출처: http://dictionary.cambridge.org/grammar/british-grammar/verb-patterns/hear-see-etc-object-infinitive-or-ing