Robbie made a semi-circle in the air with one finger. (Robbie.40)
Robbie can't talk, but notice that he has no problem communicating with Gloria. Our later robots can talk, but let's not forget that there are other ways to communicate.
"At the same time, when you sent him out after the selenium, you gave him his order casually and without special emphasis, so that the Rule 2 potential set-up was rather weak." (Runaround.148)
This is half of Speedy's problem: a decreased sense of the Second Law because Donovan gave the order too casually (the other half involves his increased sense of the Third Law). See, Asimov's robots understand English, but English can be a little ambiguous. (We'll see this issue pop up again in "Little Lost Robot," with strong language.)
Cutie laughed. It was a very inhuman laugh—the most machine-like utterance he had yet given vent to. It was sharp and explosive, as regular as a metronome and as uninflected. (Reason.55)
You could do a whole (awesome) paper on how robots speak in these stories, starting from un-speaking Robbie to playful and warm-sounding robots. But Cutie is still a pretty early robot and he still has a robotic voice. See also "His voice carried the cold timbre inseparable from a metallic diaphragm" (7).
"I sensed that an order was sent, but there was never time to receive it." (Catch that Rabbit.127)
The "positronic field" is a bit of technobabble (not even Powell and Donovan know how it works). But it's a useful reminder to us how close "language" is related to technology. That is, even writing was an invention, as were the printing press and Twitter. Communication tends to be tied to technology, and new technologies may bring new opportunities and problems. So, in the case of the "positronic field," the robots are presented with a weird situation: they sense an order, but don't receive it.
"It's your fiction that interests me. Your studies of the interplay of human motives and emotions"—his mighty hand gestured vaguely as he sought the proper words. (Liar.40)
Herbie isn't a human, so only novels can help him when he tries to understand human thoughts and feelings. This is another example of a different method of communication: Robbie can't talk, so he makes motions; Herbie needs to find out how people feel, so he reads novels.
"You told him to go away?" asked Dr. Calvin with sharp interest. "In just those words? Did you say 'Go away'? Try to remember the exact words." (Little Lost Robot.90)
As in "Runaround," part of the story of "Little Lost Robot" is not just what people say, but how they say it. Gerald Black didn't just tell Nestor-10 to leave him alone—he used a lot of swear words and harsh language. So robots aren't just sensitive to what is said; they're also sensitive to how it's said.
"Original impressionment is not everything," Calvin snarled at him. "Robots have learning capacity, you... you fool—" And Bogert knew that she had really lost her temper. She continued hastily, "Don't you suppose he could tell from the tone used that the words weren't complimentary? Don't you suppose he's heard the words used before and noted upon what occasions?" (Little Lost Robot.124)
We brought this quote out because we love that Calvin's version of "strong language" is to call someone a fool, but also because Calvin lays out clearly what we were talking about in the previous quote: robots understand language, but they also understand other aspects of communication through speech—they understand slang and tone. If you've ever tried to communicate with a machine on the phone (you know, the type that says, "say 'pay bill' if you want to pay a bill" and then never hears you correctly), you can see how advanced these robots are.
"When we come to a sheet which means damage, even maybe death, don't get excited. You see, Brain, in this case, we don't mind—not even about death; we don't mind at all." (Escape.48)
OK, so Calvin is usually right and smart, even if it takes her some time to figure out what's going on. But here she falls into the same problems that keep fouling up people's plans with robots: she's not careful about what she says. She tells Brain that humans don't mind death, so Brain figures that it's OK to kill humans temporarily. Of course, this ends with a positive turn of events—thanks to this, Brain figures out the hyperatomic drive.
And Stephen Byerley, tight-lipped, in the face of thousands who watched in person and the millions who watched by screen, drew back his fist and caught the man crackingly upon the chin. (Evidence.268)
With robots, it helps to keep in mind that there are ways to communicate besides what we say. For instance, Speedy and Nestor-10 both pay attention to how people say commands. But with humans, there's also other ways to communicate, and Byerley has just demonstrated one of the most basic forms of communication: hitting someone. This isn't just a regular punch, though; this punch communicates a lot of information about Byerley being human (maybe).
"Do you remember the Machine's own statement when you presented the problem to him? It was: 'The matter admits of no explanation.' The Machine did not say there was no explanation, or that it could determine no explanation. It simply was not going to admit any explanation." (Evitable Conflict.220)
This may be the final evolution of robot language—not only can they understand human tone and slang, but they can be purposely ambiguous in what they say. They're just like us that way.