Science

Blue light does not cause harm, that is a myth perpetuated by eyeglass corporations to sell you a product. You get more exposure to blue light from the sun than you ever will from your device screens. The only impact blue light has on you is interrupting your circadian rhythm.

and in terms of "memory" the article explains it:

This was because using the device shifted the way that people used their memory to store high-importance versus low-importance information. When people had to remember by themselves, they used their memory capacity to remember the most important information. But when they could use the device, they saved high-importance information into the device and used their own memory for less important information instead.