Perception verbs: see someone do or doing something

The idea

After active see, hear, notice or watch + object, a bare infinitive often presents the whole event; ing usually highlights activity in progress or repeated activity. In the passive infinitive pattern with see, include to: was seen to leave.

Examples

• I saw a fox cross the empty road.
• I saw a fox crossing the road as we drove past.
• We heard someone knock twice on the side door.
• I could hear water dripping behind the wall.
• Lea watched the potter shape the bowl from start to finish.
• The courier was seen to leave through the side gate.

Watch out

An ing observation does not prove the action remained unfinished later. A passive ing pattern is also possible: was seen leaving. Do not add to to active saw him leave. Not seeing an action happen is not proof that it never happened.

Try it yourself

1. Choose the correct option. I saw a fox ___ the empty road. (cross / to cross)

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   cross

   Active saw + object takes bare cross, not to cross. The sentence presents the crossing as an observed event.

2. Choose the correct option. I could hear water ___ behind the wall. (dripping / dripped)

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   dripping

   Dripping presents the ongoing or repeated sound of drops. Dripped cannot directly replace it in this active perception pattern.

3. Choose the correct option. The courier was seen ___ through the side gate. (to leave / leave)

   Show answer or example answer

   to leave

   The passive infinitive construction needs to leave. The active counterpart would be someone saw the courier leave; was seen leaving is another valid pattern with a different focus.

Use it today

Describe a sound you heard as a complete event, then a scene you noticed while passing. Explain which part you observed and choose the complement that presents that viewpoint.