I've always felt there is a very subtle difference between "start to do" and "start doing". However, most sources I've seen online say there's no difference between the two whatsoever.
If you're a learner mostly concerned about what's correct or incorrect, this question isn't really for you. All of the sentences below are correct and mean the same thing, though some (to me) feel more natural than their alternatives.
Note that unlike "start", "stop to do" and "stop doing" mean totally different things in English.
Which of the following do you consider more natural? Or do you consider them equally natural?
1A. As soon as I walked out the door, it started to rain
1B: As soon as I walked out the door, it started raining
2A: I started to learn English when I was ten years old.
2B: I started learning English when I was ten years old.
3A: I should really start to do my homework.
3B: I should really start doing my homework.
4A: As soon as someone mentioned politics, the mood at dinner started to sour.
4B: As soon as someone mentioned politics, the mood at dinner started souring.
5A: The new government started to implement reforms as soon as it came into power.
5B: The new government started implementing reforms as soon as it came into power.
I have quite clear preferences in each pair of sentences. My logic is that "start to do" implies a more spontaneous, sudden start, whereas "start doing" implies something planned beforehand. Is this just my idiosyncratic preferences?
Your third example has nuance. Both phrases work, but there are multiple implied meanings: "I haven't done my work and I will start doing it now." Or "I haven't done my work and I will start to do it from now on."
One is more towards the future and the other is more towards the present. You can still use them interchangeably though, and the difference will be clarified in context, i.e. "I will start to do my work now" or "I will start doing my work later." Basically, if you're speaking in present tense and you feel there's any ambiguity in the situation, just clarify when the action starts with "now" "later" or some context like that. Otherwise both variations feel natural.
Infinitives or gerunds in bold are the more commonly used here in Canada:
nuances aside:
1. ... it started to rain - same as - it started raining
2. ... started to learn - same as - started learning
3. ... start to do - same as - start doing
4. ... started to sour - NOT started souring.
5. ... started to implement - same as - started implementing
Thanks for both your comments - I assume your answers are "same" for all except #4, with a caveat for #3: it's a habit with "to do" but an instant decision with "doing".
It's interesting that you both had strong reactions to that one sentence (#4). It could possibly be because you both speak American English, I'm not sure - in any case, I agreed with #4 but disagreed with #3. I don't feel "to do" is natural in either context.
(It's only fair here that I disclose that I speak New Zealand English, which is based on British English)
If you (or anyone else) can think of other sentences where "start to do" and "start doing" are not interchangeable in your view, you're welcome to provide them.
In my opinion and to my knowledge, verbs such as start, prefer, hate, love and others keep the same meaning without implying anything about a particular time regardless of whether the infinitive or the gerund is used.
There are some verbs like stop (as you mentioned) or try, for example, that do have another meaning, but without implying anything about a particular time either when used with one or the other.
Verbs such as regret, forget or remember have a different meaning since they imply something in regard to the future or in regard to the past when used with one or the other.
"Remember to do your homework." is said in regard to the future.
"Do you remember doing your homework?" is said in regard to the past.
Now, strictly speaking and aside from some particular verbs, you are right to think that both of them have a subtle nuance as Michael said.
The gerund is often used for an action that happens before or at the same time as the action of the main verb.
"I suggest doing the chores another way." implies to do the chores (in another way), but now, as soon as I said it. I suggest it now, and I want it to happen now.
"I suggested doing the chores another way." implies that "we" did the chores (in another way), but before I had even suggested it, which would also imply that although we were already doing the chores another way, I "suggest" (at that time) doing them (immediately) in another different way.
The infinitive is often used for actions that follow the action of the main verb.
"I suggest to do the chores another way." implies in a near future, maybe in a couple of minutes/hours or later basically. I suggest it first, and then later we will do it.
"I suggested to do the chores another way." implies the same thing, but it was in the past.
To me, your sentences have the same meaning unless we use adverbs such as now, later (as Colin mentioned) or others to identify whether or not we want to emphasise a particular time.
@Michael Chambers: can you give examples to illustrate your point?
It's honestly surprising to me that the verb "sour" has brought everyone together. It makes me wonder if there are other such verbs that can only be used in one form.
