Hi there,
I heard that children under the age of 3 (I think it was) can’t distinguish between a drawing of a cat and the real thing. Most flashcards I’ve found on the market and several links provided within this forum seem to have only drawings or cartoons of objects. Obviously LR combats this but has anyone else heard about such research?
I haven’t heard of such research. Personally, I would just use real pictures because I want it to be an accurate representation of the actual thing.
From my own observations, I also find that babies don’t seem that attracted to cartoons, though when they reach 2+ or 3 they would prefer cartoons over real life stuff.
I am not too sure about pictures on flashcard. But from my baby’s experience, we have lots of pluffy toys for her and it’s all in cartoon, but she has no problem recognizing the real animals. Someone has told me that we should not show cartoon or drawing to babies because they will not know the real one, but to my surprise, when my baby sees a picture of real cat, she knows it’s a cat!! And same for elephant and dog. She did that when she was younger than 6 or 8 month, so I think it may be ok. But if we have real picture, why not show the real one! For pluffy, I have no choice 
For our case, my gal despite that she is only 1+, she can easily identify the type of animal whether it is a real photo or a cartoon and show use the correct sign she learnt for that type of animal. I was so surprise that she can tell the cartoon cat straight away despite what we are showing to her is a really cat initally.
I have not yet started the program, but am looking in to it for my son who is currently 3 months old. I think that I will use photos for his flashcards. I think it is a better link to what he will see in real life.
I use photos, cartoons, puppets, plastic animals…anything that resembles a cat is exactly that…something that resembles the image of a cat. And a photo of a cat is not a cat, it’s just an image or representation of a cat. I want bub to recognise an animal in all its representations.
I use only real photo’s because I believe children pick up the slight differences in things that we might not even be thinking of teaching about. For example how an Eagle’s claws look.
Cartoon picture or drawing just do not have that natural detail.
That being said a well done drawing is better than a lousy photograph but I would look for another photo!
I show my son actual photographs, cartoons, toys, stuff animals, and anything I can get a hold of. I would rather show him the real object but if I can’t any representation of the object is good. I personally think that showing objects in different forms will help the child recognize it when do see it in different forms. 
I just wanted tosay that even though I choose to use real photo’s in my presentation she can recognize a catoon, drawing or photo of a cat. Even some very poorly drawn representations that I have drawn. So I’m sure what ever is used will teach the subject just make sure it’s clear and as accurate a representation as possible.
I also prefer real photos. Some cartoons are too simplified and it does not accurately represent the real thing. Having said that I think babies are able to recognize similarity between pictures, real thing and probably cartoons. Just the other day, my daughter pointed out a lion statue in a magazine and said “grrrrr”. I’ve only showed her real lion photos.