QUESTION: Should I say I heard a baby cry or I heard a baby crying?
ANSWER: The answer may be found if we look at the big picture, that is, the whole context. Isn’t it possible for a baby to shout out a single cry, for example, a cry of delight? Isn’t it also possible and very common for a baby to cry longer, for example, until his parents figure out that he isn’t hungry but rather in need of a diaper change? If your ears perceived a single cry of delight, I think it’s correct to say I heard a baby cry. In contrast, if you perceive a baby’s cry and it’s ongoing, it seems more accurate to say I heard a baby crying. My first point is that the choice between the base verb (bare infinitive) and the -ing form following a verb of perception and its direct object is made based on whether we are focusing on the completion (base verb) or process (-ing form) of an action.
Here are additional examples that support the above conclusion:
I saw my friend cross the finish line, and I shouted, “You did it! You won!” (completed action)
Witnesses saw the man enter the building at 12:00 and leave the building at 12:30. (completed actions)
My face turned red with anger and embarrassment when I heard them talking about me. (process)
I saw the man going in as I was going out. (process)
However, there’s more to consider. For instance, a man might say to his beloved, “I love to hear you laugh.” I don’t feel this is a matter of completion versus process. This is an expression of what he likes. This falls into the category of preferences, habits, and repeated actions. My second point is that the base verb (as opposed to the -ing form) is more appropriate if what is being perceived is a regularly occurring action or if the speaker is using the verb of perception in a general sense.
Here are additional examples to support my second conclusion:
As a child, I got used to hearing my dad sing in the shower. (regularly occurring action)
When was the last time you just relaxed and watched the clouds move across the sky? (general perception)
The exception to my second conclusion would be a desire to emphasize frequency and possibly annoyance. Example: You say that there’s nothing going on between you and Mary, but I always see you talking to her. Are you just friends or what? This distinction is similar to the one between the simple present and the present progressive tenses: He often sings in the shower. (neutral) / He’s always singing! Does she ever stop? (complaint)
There could be a third point, one that is supported by the folks at Eslgold.com. They propose that the choice between the bare infinitive and the -ing form is decided by the speaker’s focus: If the act of perceiving is the focus, we use the bare infinitive: I heard the door open. If the focus is on what is being perceived, then we use the -ing form: I heard the door opening. I would add to this that context is always the deciding factor. We need as much context as possible to choose the more appropriate form. These same two examples about the door opening could be used to support my first point about completion versus process. However, I would agree with the argument of focus if more context is given to suggest that focus is important. For example:
Father: You came home rather late last night.
Son: Not really. It was around midnight.
Father: Actually, I think it was more like 2 in the morning! I heard you come in. I heard the door open, and when I looked at the clock it was after 2.
Husband: Huh? Why did you wake me up?
Wife: Shh! I thought I heard the front door opening. Maybe it’s a burglar!