⚙️ Grammar · Verb Patterns: -ing & Infinitives
Perception Verbs (See Him Do vs See Him Doing)
I saw him leave or I saw him leaving? After see, hear, watch, notice and feel, the tiny difference between the bare infinitive and the -ing form changes what you actually witnessed.
Grammar › Verb Patterns: -ing & Infinitives › Perception Verbs (See Him Do vs See Him Doing)
The rule in one sentenceAfter see, hear, watch, notice and feel + object, use the bare infinitive for a complete action you witnessed from start to finish (I saw him leave) and the -ing form for an action that was in progress (I saw him leaving).
What’s the difference?
Perception verbs describe what your senses pick up — and English lets you report that in two ways. Both are correct; they simply paint different pictures.
With the bare infinitive (no to), you claim the whole event: you watched it begin, happen and finish. In Nine Queens, we see two strangers meet, team up, and spend a single day running scams across Buenos Aires — one complete action after another.
With the -ing form, you only claim a slice of the event: the action was already under way when your senses caught it, and it may have continued afterwards. In Tell No One, the hero opens a mysterious video link and sees a woman looking straight into the camera — a woman identical to his wife, who died eight years earlier. He doesn’t see the whole recording session; he catches her mid-look.
🎬 Compare: in Port of Shadows, “we see the deserter arrive in the foggy harbour of Le Havre” (a complete event — he wasn’t there, and then he was) vs. “through the mist, we see him walking along the quay” (we catch the action in progress).
Same man, same fog — the verb form tells your listener how much of the action you witnessed.
One more thing the two forms share: perception verbs in the active voice never take to + infinitive. I saw him to leave is impossible. The choice is only ever between leave and leaving.
How to build it
Bare infinitive — the complete action
We watched the newlyweds board the barge at the start of L’Atalante.
He didn’t see anyone send the mysterious email in Tell No One.
didn’t + perception verb + object + base verbDid you hear the audience gasp at Tell No One’s final twist?
Did + subject + perception verb + object + base verb-ing form — the action in progress
In I Am Cuba, you watch the camera gliding down the side of a hotel and into a swimming pool.
You don’t notice the shots changing — some takes run for minutes.
don’t + perception verb + object + verb-ingCan you feel the tension building as the camera floats above the funeral procession?
can + subject + perception verb + object + verb-ingWhen to use which
Bare infinitive — you saw it all
- The whole event, beginning to end: We watched the two con men in Nine Queens plan the whole scam.
- Short, sudden events: The audience heard a phone ring — then Tell No One’s plot exploded into life.
- A sequence of completed actions: In Monster, we see the same days unfold three times — first through the mother’s eyes, then the teacher’s, then the child’s.
-ing form — you caught it mid-flow
- Already happening when you noticed: Through the fog of Port of Shadows, we noticed a figure walking towards the docks.
- Long or continuous background action: In Pépé le Moko, the police can hear the market traders shouting all through the Casbah of Algiers.
- Deliberately incomplete — you looked away: I only caught a minute of Monster, but I saw the two boys playing in the woods.
The perception verb family
These are the verbs that follow this two-pattern rule. Learn them as a group — they all take an object + bare infinitive or -ing, and never to + infinitive in the active.
Visual guide
Teacher Teddy’s illustrated guide to this rule is being drawn — the full swipe-through infographic will appear here soon.
Common mistakes
❌ I saw him to leave the cinema before Monster finished.
✅ I saw him leave the cinema before Monster finished.
Perception verbs never take “to” + infinitive in the active voice — it’s the bare infinitive or -ing, nothing else.
❌ We heard the audience to gasp at Tell No One’s twist ending.
✅ We heard the audience gasp at Tell No One’s twist ending.
A gasp is a short, complete event heard from start to finish → bare infinitive.
❌ I glanced at the screen for a second and saw the couple dance on the deck of L’Atalante.
✅ I glanced at the screen for a second and saw the couple dancing on the deck of L’Atalante.
A one-second glance can only catch the action mid-flow — you didn’t see it start or finish → -ing.
❌ In The Teachers’ Lounge, a member of staff was seen take money from a wallet.
✅ A member of staff was seen taking money (or: was seen to take money).
In the passive, the bare infinitive is impossible — it becomes “to” + infinitive, or stays as -ing. See the tricky cases below.
Exceptions & tricky cases
Four details that separate a good B2 answer from a perfect one.
1. The passive flips the bare infinitive to “to”. Active: They saw her leave. Passive: She was seen to leave — never “was seen leave”. The -ing form survives unchanged: she was seen leaving.
✅ In The Teachers’ Lounge, the whole school argues about what exactly was seen to happen on one short video clip.
2. See / hear + that-clause means “learn” or “understand”, not perception.
✅ I see that Monster won the screenplay prize at Cannes. (= I’ve learned this — I didn’t literally watch it.) Compare: I saw the boys run to their hideout — real, physical seeing.
3. With “can see / can hear”, English strongly prefers -ing. These describe an ongoing sensation, so the in-progress form fits naturally.
✅ From the first frames of Port of Shadows, you can see the fog rolling in over the harbour.
4. “Smell” and “find” only take -ing. There is no bare-infinitive option for these.
✅ In I Am Cuba, a farmer sets fire to his own field — you can almost smell the sugar cane burning. (Never “smell the cane burn”.)
Practice: choose the right form
Eight quick questions. Pick the answer you’d actually say — you get the explanation either way.
1. We watched the newlyweds ___ aboard the barge in L’Atalante’s opening scene.
After watch + object, use the bare infinitive — “to” is never possible here.
2. I only caught a minute of Monster, but I saw the two boys ___ in the woods.
You saw a slice of the action, not the whole event → -ing.
3. We watched the con men in Nine Queens ___ their scam from start to finish.
“From start to finish” = the complete action → bare infinitive.
4. Through the fog of Port of Shadows, we suddenly noticed a figure ___ towards the docks.
The walking was already in progress when you noticed it → -ing.
5. Did you hear the audience ___ when Tell No One’s twist was revealed?
A gasp is short and complete, and “to” is impossible after hear + object → bare infinitive.
6. In The Teachers’ Lounge, a member of staff was seen ___ money from a wallet.
In the passive, the bare infinitive disappears — it’s “seen taking” or “seen to take”.
7. In I Am Cuba, you can watch the camera ___ down the side of a hotel for a full minute.
“For a full minute” and “can watch” both point to a continuous, in-progress action → -ing.
8. For most of Pépé le Moko, the gangster is never seen ___ the Casbah of Algiers.
Passive voice → the bare infinitive becomes “to” + infinitive: “seen to leave”.
Keep going
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