Personal Infinitive with Perception Verbs (ver, ouvir, sentir) | Portuguese (Brazil) Grammar

When you want to say "I saw the kids play" or "I heard the birds sing," Brazilian Portuguese gives you the personal infinitive as one of its main tools. After verbs of perception — ver (see), ouvir (hear), escutar (listen to), sentir (feel), observar (observe), notar (notice) — the embedded verb can take its own subject and inflect: Eu vi as crianças brincarem. This page covers that construction and the all-important contrast with the gerund (brincando), which expresses something subtly different.

The good news for English speakers: the structure maps onto English fairly closely. "I saw the children play" puts the perceived doer (the children) right after the perception verb, and so does Portuguese. The twist is that Portuguese can inflect the embedded verb, and it offers a second option — the gerund — that changes the flavor of what you're describing.

The basic pattern

Perception verb + perceived subject + personal infinitive. The infinitive inflects to agree with the perceived subject.

Eu vi as crianças brincarem no parque.

I saw the children play in the park.

Ouvi os pássaros cantarem de manhã cedinho.

I heard the birds sing early in the morning.

Senti as paredes tremerem quando o caminhão passou.

I felt the walls shake when the truck went by.

In each case the perceived subject is plural (as crianças, os pássaros, as paredes), so the infinitive takes the -em ending (brincarem, cantarem, tremerem). With a singular perceived subject, the infinitive shows no ending — it looks like the plain infinitive:

Vi o menino cair da bicicleta.

I saw the boy fall off the bike.

Ouvi a vizinha cantar no chuveiro.

I heard the neighbor sing in the shower.

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The inflection only becomes visible in the plural (-em) and the nós form (-mos). With singular subjects (o menino, a vizinha) the personal infinitive is identical in shape to the plain infinitive — but it's doing the same job: carrying its own subject.

The big contrast: infinitive vs. gerund

Here is what makes this topic genuinely interesting. Brazilian Portuguese lets you express the same scene two ways, and the choice is meaningful.

Eu vi as crianças brincarem.

I saw the children play. (the whole event — they played, I saw it happen)

Eu vi as crianças brincando.

I saw the children playing. (in progress — I caught them mid-play)

The personal infinitive (brincarem) presents the action as a discrete, complete event: something happened, and you perceived it as a whole. English captures this with the bare infinitive: "I saw them play."

The gerund (brincando) presents the action as ongoing, a scene unfolding while you watched. English captures this with the -ing form: "I saw them playing."

This maps remarkably well onto the English "see them play" vs. "see them playing" distinction, which is one of the few places where an English instinct actually helps you in Portuguese.

Ouvi você chamar meu nome.

I heard you call my name. (one call, a complete event)

Ouvi você chamando meu nome.

I heard you calling my name. (you were in the middle of calling)

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Think "event vs. scene." The infinitive zooms out and shows you the action as a single happening (I saw them do it). The gerund zooms in and shows you the action in progress (I saw them doing it). Both are correct and common — Brazilians switch between them effortlessly.

When the difference matters most

For a completed, bounded action — especially something brief or whole — the infinitive is the more natural choice:

Vimos o sol nascer atrás das montanhas.

We watched the sun rise behind the mountains. (the full event)

A gente ouviu a porta bater.

We heard the door slam. (a single, sharp event)

For an action you observed while it was already happening — a backdrop, a process, a continuous activity — the gerund fits better:

Encontrei meu pai assistindo ao jogo e gritando com a TV.

I found my dad watching the game and yelling at the TV. (ongoing scene)

Cheguei e vi todo mundo dançando na sala.

I arrived and saw everyone dancing in the living room. (a scene in progress)

Many sentences accept either with no real difference; the contrast becomes sharp mainly when the bounded/ongoing distinction is communicatively relevant.

A subtle point: the embedded subject's position

With perception verbs, the perceived subject sits between the perception verb and the infinitive — exactly where you'd expect from English word order. You do not need que, and you do not need a preposition.

Observei os atletas se aquecerem antes da corrida.

I watched the athletes warm up before the race.

Note se aquecerem: with a reflexive verb, the pronoun se stays attached, and the infinitive still inflects for the plural subject (os atletas → aquecerem). This is a place where the personal infinitive shines, because the -em ending and the se together make it unmistakable who is warming up.

Why Portuguese works this way

The reason the infinitive can carry its own subject here goes back to the personal infinitive's core function: it lets a non-finite verb behave almost like a small clause, complete with a subject, without the heaviness of a full conjugated clause introduced by que. After a perception verb, you are reporting a perceived event, and Portuguese treats that perceived event as a compact unit — perceived-subject plus infinitive — rather than as a full subordinate clause. The gerund offers the alternative "ongoing" framing because gerunds inherently express action-in-progress. So the two options aren't arbitrary; they fall straight out of what infinitives and gerunds fundamentally do.

Compare with English, where "I saw them play" (bare infinitive) and "I saw them playing" (gerund) carve up the same conceptual space. The difference is that Portuguese can also inflect its infinitive (brincarem) to make the plural subject explicit — something English cannot do.

Common Mistakes

❌ Eu vi as crianças brincar no parque.

Marginal — with a plural perceived subject, careful Brazilian Portuguese inflects: brincarem.

✅ Eu vi as crianças brincarem no parque.

I saw the children play in the park.

The plain infinitive here is heard colloquially, but the inflected form is the standard and clearer choice when the subject is plural.

❌ Ouvi que os pássaros cantarem.

Incorrect — perception verbs take the subject directly, with no que.

✅ Ouvi os pássaros cantarem.

I heard the birds sing.

This is a direct English-transfer error: English never says "I heard that the birds sing" to mean a perceived event, and neither does Portuguese in this sense. Drop the que.

❌ Vi as crianças brincandem.

Incorrect invented form — the gerund (brincando) never takes person endings.

✅ Vi as crianças brincando.

I saw the children playing.

Only the infinitive inflects. The gerund is always invariable: brincando, never brincandem.

❌ Senti as paredes tremer e tremendo ao mesmo tempo.

Incorrect — pick one form per clause; don't combine the infinitive and gerund.

✅ Senti as paredes tremerem.

I felt the walls shake.

❌ Observei os atletas aquecerem-se.

Marginal/formal — in BR the pronoun normally comes before: se aquecerem.

✅ Observei os atletas se aquecerem.

I watched the athletes warm up.

Key Takeaways

After perception verbs (ver, ouvir, sentir, observar, notar), the embedded verb can be a personal infinitive that inflects for its own subject: vi as crianças brincarem.
No que and no preposition: the perceived subject goes directly between the perception verb and the infinitive.
The infinitive frames the action as a complete event ("saw them play"); the gerund frames it as ongoing ("saw them playing"). Both are correct.
The inflection is only visible in the plural (-em) and nós (-mos); singular subjects look like the plain infinitive.
The gerund never inflects — brincando, never brincandem.

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