Ruby flew down the hall, careened around the corner, and stopped just briefly to jump on me before charging off again. His pointy ears and tail bobbed and wagged in rhythm as he ran laps around the house. I had just come through the door on my first trip home from college and it was the best welcome-home I could ask for. Ruby’s exuberance over seeing me again, after our months apart, is a favorite memory from my college days.
Remembering my reunion with Ruby is an example of an episodic memory – recalling an experience. Such autobiographical memories – tied to specific places, times, and emotions – are integral to our lives as humans. There are other types of memory, for example, your phone number or each State’s capital city are semantic memories – memories for facts that build over time. But, as perfectly described in the lyrics of Bob Dylan’s Precious Memories, episodic memories are the ones that “flood the soul.”
The question for researchers in a recent study published in Current Biology is whether other animals besides humans share the ability for episodic-like memory. Could Ruby encode and recall memories of our experiences together something like I do? The first task for Claudia Fugazza and her colleagues was to design a memory test that would target episodic memory by ruling out reliance on learning, which would instead tap into semantic memory. Memory researchers agree that a crucial aspect of episodic memory is that memories are saved without the knowledge that they have to be remembered in the future. So, any test of episodic memory has to be unexpected.