Though life expectancies these days may no longer be short enough to truly consider thirty as being “middle-aged”, my experiences with my memories are no longer the same that they once were. Perhaps it is the amount of stress that comes with being a parent of two, a co-owner of a business, suffering from chronic illnesses including an autoimmune disease, or just the simple fact that I am a full-time college student (whether on its own or in combination with these things) but I feel that there truly is a difference in the way that our memory works later in life as opposed to when we were younger.

Mental time travel refers to the recollection of events that have happened to us previously and which are stored as episodic memories. Personally, this term for episodic memories has come to be my favorite part of my studies so far involving memory and its connections to psychology and the brain. It truly makes sense to describe the process of recalling episodic memories as a sort of mental time travel since episodic memories, as opposed to semantic memories, store the exact time at which the memory was stored. It is for this reason, that recalling those memories feels almost as if we are turning the dial to the time in which that memory was created and can often even recall the feelings we associated with the creation of the memory. In contrast, semantic memory is the recollection of facts gathered from the time we are young and are indisputable nuggets of information that aren’t associated with emotion or personal experience(s).

One way to establish the difference between semantic memories and these time-travelling episodic memories is to compare an example of each. A semantic memory that I possess as an almost-thirty mother of two can be found in the song lyrics of way too many nursery rhymes and themes for children’s shows. I don’t particularly recall when these memories were officially “stored” since my oldest child is almost ten and my youngest is three, so sometimes I can’t remember if I knew a song from my first child or my second child, but you better believe that I do know just about every word, and really wish that I didn’t.

My episodic memories on the other hand, time-travel me back to the exact moment that I first held my infants in my hands, recalling their exact birth times, birth weights, lengths, head circumferences and the euphoric feeling – quite possibly somewhat impacted by meds – that I felt when holding them for the first time and gazing into their tiny little squinty blue-eyes. Now, I can hardly tell you what sizes they are for any of those things since it changes so frequently and honestly, if you ask me what time it is, I probably won’t know the answer to that either!

Joking aside, the differences are surprisingly different to me now when recollecting these episodic memories than they were when I was much younger. For instance, when I was a teenager, I know for a fact that episodic memories were easy to recall from as far back as toddler and elementary years. If I attempt to recall those memories now, everything is a bit hazier. It’s as if my episodic memories are much stronger in my ability to travel back in time if they are attached to much more distinct triggers, whether emotional, auditory, olfactory or otherwise.

For example, I can smell gas or antifreeze and know right away what it is. I also could tell my friend that her catalytic converter was going bad because I could smell a very distinct and familiar smell from during high school when my friend Joe had the same issue with his Jeep Grand Cherokee. I instantly remembered that weird guy and his weird car with the weird smell which helped me to help my friend. If I hear a song that was playing during a special moment or memory shared with my husband or one of my children, it’s very easy for me to recount the events of that memory with them and to feel the same good feelings that I did when the memory was created. Memories that lack these triggers, however, seem to be less easy to retrieve for me now that I am later in life.

Since episodic memories include memories for events in which we personally had participated, they can come from things such as our wedding day, the birth of our children, graduation, prom, or even what we’ve had for breakfast or dinner the night before. Often, it’s not as easy for me to recall the latter two choices as it is for me to recall the rest of the things I’ve named previously. I’ve always wondered whether this is because my brain stores it as somehow less important and therefore it is not as easily recollected or whether I’ve just recalled the information for other events more frequently, so they are more readily available for time travel than the other memories.

“Perhaps in recalling our memories and speaking about them frequently, they cross into the category of semantic memory and are then considered to be both”, I wondered. Well, I wasn’t completely wrong. Since our memories are initially created as episodic and eventually become semantic, it seems plausible that the two types of memories are clearly linked in some way. Both are long-term memories, explicit, or declarative, in nature and therefore are conscious memories but beyond this, there must be an explanation for why memories seem to shift between being episodic and semantic.

So, I set out to determine why my time-traveling skills are less adequate now as they were in my teens or twenties and moreover, why some memories appear to only retain the semantic memory now when they once were episodic memories in the past. Since I’m currently battling a nasty stomach virus (thanks once again to my autoimmune disease) and haven’t had power all weekend due to the winter storms in our area, my research is limited to our Cognitive Psychology textbook and all information in my blog post is supported through this single resource.

Endel Tulving made some distinctions between episodic and semantic memories. Tulving observed that forming a new episodic memory is affected by information within semantic memory. Moreover, he suggested that the memory must pass through the semantic memory before it can be cemented into long-term memory as an episodic memory. Through his studies, we can discern that there is a steady movement of memories from episodic to semantic, especially during childhood when we are continuously learning new things. For example, children who play with kitchen sets, toy phones or keys, and even baby dolls, can learn things through their pretend play which will last in their long-term memory as knowledge that will help them to use a kitchen, phone and keys and eventually care for a child more properly when they are adults and face these things.

Even more fascinating to me was learning that semantic memory is generally derived from episodic memory which makes sense since we typically learn new facts or concepts from our experiences. Our episodic memory is considered to reinforce semantic memory which also makes sense since I was able to recall the smell of the catalytic converter going bad and was therefore able to assess the situation based on a smell from back in high school.

Researchers seem to agree that there is some sort of transition that takes place from episodic memory to semantic memory, in which episodic memory reduces its sensitivity and association to events, so that the information can be stored as general knowledge. For instance, we all know how to use a remote control to operate the television, but don’t remember exact timing of when we learned to use a remote for the first time whether it was during our earliest years when we played with a toy remote or when it was that first week of having our new cable box and fumbling around with the remote until we learned its basic functions.

I suppose the answer to my question is clear now that memories which were once more episodic must have transitioned into semantic memory, storing only the knowledge from the memory which is deemed most important to retain. Perhaps certain triggers could bring the memory to surface more readily because the same areas of the brain that were active during the creation of the memory are being used during the recollection of the memory but this still doesn’t answer my question as to why I can’t remember some things at all from when I was young unless that information has just become lost like the match to several pairs of my children’s socks. I think though, that it likely has to do with our brain being more focused on what is necessary for survival and honestly – age just makes things work a little less efficiently overall – including gravity within the human body. Nevertheless, it was very interesting to learn about the connection and transitions between episodic and semantic memories.

Goldstein, E.B. (2017). Cognitive Psychology: Connecting Mind, Research, and Everyday Experience (4th edition). Stamford, CT: Cengage Learning