choice of speak vs. talk

Donoto wrote:

Could you comment (idiomatic/not idiomatic, different meanings, etc) on the choice of speak/talk in the following sentences?   (1)   Who did this?  Now, speak/talk to me! Someone speak up!: would be most appropriate. Speak to me: It doesn't sound quite right. Talk to me: It implies that  I want to have a conversation with you.   (2)   He hesitated, and then spoke/talked. Spoke is correct. Or you can say: He hesitated, and then we talked.   (3)   It’s ridiculous that nobody got a raise this season.  As a union representative, I’ll go and speak/talk to the manager. In the U.S. we say talk in this situation, but speak would be okay to.   (4)   You don’t understand. Let’s speak/talk. Talk is correct.  Speak is more of a one-way communication.   (5)   He spoke/talked in front of a crowd of angry commuters. Spoke is correct.    (6)   The professor spoke/talked about the ecology of the lake. Either is okay.  I would be more inclined to say the professor spoke about...  Whereas, I'd say we talked about (discussed) the topic of...   (7)   Don’t speak/talk to me like that. Talk.   (8)   We spent hours speaking/talking about our childhood. Talking.   A related question: Basically, to speak as opposed to talk sounds more generic, meaning to utter words, not necessarily telling stories or engaging in conversations. If that’s true, how come: I think 'speak' is a little more formal, and 'talk' is used to describe two way conversations.   (9) When did the baby begin to talk?   is more idiomatic than   (10)   When did the baby begin to speak?   Or am I wrong about (9) and (10)? You are correct.  A baby does not give a formal speech.  But a baby can begin to engage in a conversation by responding to simple questions like "what is your name?"

Speak and talk have almost the same meaning.
In general, "speak" is used for one person and "talk" is used for conversations, or potential conversations.
This is a general rule. You should still say "Shut up when i'm talking!"

 The main thing to remember is that while 'speak' may or may not take a direct object, 'talk' never does. I can say "I speak English," but not, "I talk English." On the other hand, I could either 'speak' or 'talk' to my friend. In this case, it's merely context that determines which one to use: 'speaking' is generally a one-way communication while 'talking' implies a conversation or discussion of sorts. Hope that helps!