“See / hear someone do / doing”

After verbs of the senses — see, hear, watch, notice, feel, listen to — you can use object + base verb or object + -ing. There is no to in active sentences, and the second verb doesn't change for tense.

💡Only the sense verb changes for tense; the second verb stays as the base form or -ing: saw him leave / saw him leaving, not “saw him left”.

1. Base verb — the complete action: you see or hear it from beginning to end, or a series of actions one after another

• I saw him get off the bus and walk into the bank.

• We watched the sun go down over the sea.

• Did you hear the phone ring?

2. -ing — an action in progress: you only catch part of it, not necessarily the beginning or the end

• I heard someone singing in the shower.

• When I walked in, I noticed two kids hiding behind the sofa.

• I could feel my heart beating fast.

3. Very short or long actions: a quick action (a slam, a fall, a single shout) usually takes the base verb; a long or repeated action usually takes -ing

• I heard the door slam.

• I heard the dog barking all night.

4. smell, catch, find take -ing (not the base verb)

• I can smell something burning!

• My mum caught me eating sweets before dinner.

• I found him sleeping on the sofa.

Often both forms are grammatically correct — the form you choose changes the meaning.

• I watched them play the whole match.

• I watched them playing for a few minutes, then left.

• I saw him cross the road.

  he reached the other side

• I saw him crossing the road.

  he was in the middle of crossing

💡When in doubt, ask yourself: did I witness the whole action from start to finish? Yes → base verb. Only part of it → -ing.

• With see, hear, smell and feel we often add can / could: I can hear the neighbours arguing again.
• In the passive, to comes back (fairly formal): He was seen to enter the building. The -ing form stays the same: He was seen entering the building.
• see / hear + that + clause has a different meaning: realise or learn something, not witness it directly: I saw that she was upset. / I heard that you got a new job.
• The person takes the object form: heard him singing, saw them leave (not he, they).

• ✗I saw him to leave the office.

  ✓I saw him leave the office.

  No to after see / hear in active sentences.

• ✗We heard her sang a beautiful song.

  ✓We heard her sing a beautiful song.

  Don't put the second verb in the past.

• ✗I watched him crossed the road.

  ✓I watched him cross the road.

  Don't put the second verb in the past.

• ✗I heard he singing in his room.

  ✓I heard him singing in his room.

  Use the object form (him).

• ✗I can smell something burn.

  ✓I can smell something burning.

  smell takes -ing.