The hippocampus is the brain’s primary gateway to memory. Essentially, all new information must pass through this neural structure in order to be converted into consciously accessible long-term memory.
Lining the hippocampus are millions of tiny neurons called “place cells.” These cells continuously and subconsciously encode both the spatial layout of whatever objects we are interacting with and our physical relationship to those objects. For instance, if I were to place you in a maze, place cells would map out not only the global pattern of the maze but also your unique location within that pattern as you walked through the maze.
As a result, spatial layout is an integral aspect of all newly formed memories. This is the reason why, when it comes to reading comprehension and retention, hard copy always beats digital.
Print ensures that material is in an unchanging and everlasting three-dimensional location. You may have noticed that after reading from physical media, you can typically recall that a particular passage of interest is “about halfway through the book on the bottom, right-hand page.”
The unvarying location is embedded within our memory and can be used to help trigger relevant content in the future. Digital media have neither an unchanging nor an everlasting spatial organization. When reading a PDF document, words will begin at the bottom of the screen, move to the middle, then disappear out the top. When content has no fixed physical location, we lose a key component of memory and cannot draw upon spatial organization as a cue to recall content in the future.
Modern e-readers allow users to “flip” (rather than scroll) through the “pages.” Although a step in the right direction, this still omits the important third dimension of depth, which allows for the unambiguous triangulation of information.
If your primary purpose for reading is not memory (for instance, if you’re searching for key terms), then digital tools will often prove more effective than print. Furthermore, if you have a physical or mental impairment which necessitates the need of text interactivity, then digital tools may be essential.
However, if your aim is learning and if you have the luxury of selecting between different media, then print it out.
Might be of interest: https://www.psychologytoday.com/us/articles/202407/5-ways-to-help-your-brain-learn-better