Memory Takes a Lot of Mental Resources
There are two effects that take place when retaining memories that take place when involved in a relatively long task (movies, conferences, extended conversations etc.). The first being the Recency Effect, which dictates that someone is more likely to remember the ending of a talk/movie than the beginning. Seems fair. Then there's the Suffix Effect, which dictates that if you get distracted during the middle to end of a talk/movie, you're more likely to remember the beginning of it. This chapter also goes into one of the major theories on the purpose of dreams, which is that they are a way of categorizing and consolidating memories from your waking hours. Like dreams, which are hard to remember at times, abstract concepts such dreams are harder to remember than "concrete" words, such as "chair" or "table." Mostly because these are things that we interact with physically on a daily basis. Unlike concepts we don't consciously interact with.