Just wanted to add a bit more to the two good answers above. In the second statement, the difference is the word "did." When you use the word did in this way (before the word), it puts a strong emphasis on the fact the action was done. Generally this is taken as "This was done, despite something else" For instance: Mother: "Why didn't you take out the trash when I asked you to?" Child: "I did take out the trash but..." Another example: Person A: "Did you speak to Tom today?" Person B: "No, but I did speak to him yesterday evening." The use of the word "did" in these statements reenforces and confirms them. So, unless there is some reason to reenforce or confirm them, it sounds very awkward to use them.

Both are equally right, but as Vasilis says the emphasis is slightly different. There is nothing particularly Scottish about the second sentence - it is just as likely to be said by English people.

Hi Anna. As it seems to me, 'i did see him yesterday' is more emphatic than the first alternative and would suit better as an answer to the question : ' you didn't see him yesterday, did you ? '

Ahh, sorry. I'm having an off night clearly. I meant (before the verb), not (before the word). Before the word isn't very helpful haha