There have been a vast number of studies done on infants and their knowledge of numbers. Most research confirms that infants do in fact have a profound innate sense of number, both in abstract and finite ways. Infants as young as 49 hours can accurately match up images with a certain number of objects, with sounds that contain the same number ("ra, ra, ra, ra") as the number of objects in the image. Because the sounds are abstract, or visibly there, we can see that infants as young as 49 hours have some abstract numerical sense as well as concrete numerical sense shown by their recognition of the image with the corresponding number of objects. Similarly, infants around the age of 7 months can also match up images of random objects.