There has been an increasing number of articles, both academic and popular, discussing the affect and effect on the brain. One of the key findings of this has been that those raised with the internet retain how to access information rather than the information accessed. There have also been studies that show that retention and comprehension is lessened through digital mediums. Some of the studies have compared traditional book reading vs tablets and e-readers and others have compared university students that hand write their notes vs typing lecture notes on a laptop. These studies have shown consistently that there is a greater degree of retention and comprehension of information when read in traditional books and written by hand. A search for "the effects of google on the brain" will yield a plethora of results, of which I appreciate the irony.
The research is more in favor of books right now than it is of the internet. This also translates into handwriting. While the internet does provide more visual cues, supposedly making it easier to process the information, it is not confirmed whether it does the same for its retainment.
Speaking from personal experience over many decades of reading books and similar media, I find I have good retention from the act of reading. My retention is good enough that years later, simply reading a few sentences of a book will be enough for me to recognise that I have already read it, and that I can recall much of what the book was about. When I read academic papers, my retention is certainly better when I have printed the paper than if I read it from a screen or tablet.
When it comes to writing, when I write notes, I tend to have excellent recall, but when I type something, there certainly seems to be a lesser level of recall.
However, since I have many more decades of experience of reading paoer based work than from screens and tablets, that may have a greater impact due to the conditioning effect. Similarly with writing versus typing.
It might be interesting to compare how very young people who have not experienced paper based reading and writing systems cope when presented with reading and writing in what to them would be a new medium in paper based reading and writing.
Many books have been carefully evaluated and they are relaible sources of information if they are not tampered with physically. Most of the information on the internet have not been subjected to proper scrutiny or evaluation, unless the online journals and other online resources that have been peer reviewed. There are some books that are difficult to get by online and/or vice versa.
Therefore, personally, I carefully select my sources of information from both sources for my teaching and research activities. However, which one is ingrained in my memory? Books
Personally, information from books retained more in my memory than those found on the Internet. I can internalize pieces of information from interesting books than just surfing the internet.