Try it
Watch how a language model actually picks its words
Below is a working language model, a small n-gram model to be precise. It solves the same basic task as the large ones, predicting a likely continuation, but by a different technique: counting which words have followed which before. Switch the training set and you can see for yourself how much the amount of data decides.
Pick a word and the machine will show which words most likely follow it.
What is actually happening here
01
The machine counted word pairs
It went through the text and noted which word followed which, and how many times. That is all it knows. It does not know what any of the words mean.
02
You choose, the machine counts
The machine looks at the last two words and finds their continuations in its table. If it has not seen that particular pair, it settles for one word. The percentage says how often the continuation appeared in the data.
03
Switch the data and see the difference
The same algorithm, two different training sets. With the large one the sentence sounds like English. With the small one it falls apart and starts reciting the source text from memory. The algorithm did not change, only the amount of data.