Actually memories are often linked to deep emotion. Often pain but it can be associated with joy as well. The adrenaline causes the mind to open up in a way that it otherwise runs on auto pilot. My first memory is associated with pain. It is not because of a photo. I was 4 years old and it was being dropping off by my Mother for my first day of school. I cried for an entire hour. I can still see the piano in the corner.. the sun coming through the window. Trauma induces a sort of scar if you will to the moment. Causing what we call a "memory". This can go in a positive way (amazing moments) or a negative way (bad moments). If you read through the responses there are 3 responses types. A really bad moment (sick in the hospital), (high fever mother splashing water), really happy moments (a huge bag of toys), (Donald duck), and then you have the all around jokers with their My teacher had huge guns comment which we all know is just to sound funny. lol. I have done massive research on it and could talk about it for hours. But for now I leave you with this article if your bored. And that is my 2 cents on it.

https://www.nature.com/news/fearful-memories-haunt-mouse-descendants-1.14272