Everytime you spend time with content, there are two things happening. Either you are consuming or you are absorbing. Sometimes both.
Consumption, you remember. The reel your friend sent you this morning. The photo or video you opened to watch. An article you searched to read.
Absorption is different. This happens mostly unconscious. The half second of a stranger's holiday photo, a celebrity's latest new car, someone screaming negativity about their life, the tone of a comment you scrolled past, 1 min stimulations, 100 different stories in seconds.
These are not memories. They become your mood, your thoughts.
By the time you put the phone down, you cannot list what you absorbed. But your nervous system can.
Every app I have used measures consumption. Watch time. Scroll depth. Sessions per day. Minutes per session.
I have never seen one measure absorption. Because absorption is harder. You cannot ask the user "how do you feel after using this product" and get a clean number. The mood does not arrive on the homescreen. It arrives forty minutes later, in the kitchen, as a low you cannot explain.
Building for the residue
I think the next generation of consumer products has to take this seriously. Not as a wellness add-on. As a core design question.
A few things I would start with, if I were building:
Ask the user how they feel after, not just during. A check-in twenty minutes after a session, not inside it. The session is the wrong moment, the user is still in the loop. The later, is the honest moment.
Treat repeated low-mood signals as an engagement failure, not a content preference. If a user keeps watching a category and keeps feeling worse afterward, the algorithm should read that as misalignment, not affinity. Right now most algorithms read it as the opposite.
Build friction around the unprotected moments. The first hour after waking. The transition out of focused work. Before sleep. These are when absorption is highest and resistance is lowest. A product that respects this would slow down, not speed up, in these windows.
Make the residue visible. Show users their post-session mood trend the same way fitness apps show heart rate. Once a user can see what a 40-minute session costs them three hours later, they will choose differently. Not because the product told them to. Because they could finally see it.