Today I started looking for info on the net about why people keep photos. There’s a lot of thoughts out there on this topic, for example:

http://youthcoders.net/photo/theory/979-why-do-people-keep-photographs.html

However, more academic discussion about the underlying reasons were harder to find. There is a site which, among other things, summarises aspects of  “The Psychology of photography” which is relevant but not exactly spot on:

http://dynamics.hubpages.com/hub/The-Psychology-of-Photography

I found a piece in the Psychology Today site which describes a paper by  philosopher Robert Hopkins of the University of Sheffield on “what’s special about photographs?”

http://www.psychologytoday.com/blog/maybe-its-just-me/201012/whats-so-special-about-photographs

I also came across a very detailed presentation about hoarding which seems to have some sort of relationship to the question:

http://www.hoardingsqualorconference.com.au/2009/files/presentations/Psychology%20of%20Compulsive%20Hoarding%20-%20Dr%20Christopher%20Mogan.pdf

I think I’ll have a more detailed read of the above links and then maybe contact somebody working in the area to try and have a brief discussion on the subject.