Arbitrary but related

Many of the things that we need to remember are related only arbitrarily. Consider:

• You're at a party, and your wife introduces to one of her co-workers whom you've never met before. You smile, shake hands, and try frantically to remember that this new face belongs to Alice.
• You exit the mall, bags in hand, and are confronted with a sea of cars and a burning question – Where did I park?
• You know that you've got two meetings this afternoon, but were you supposed to get coffee with your friend before or after chatting with your advisor?

Memory binds the pieces of these experiences together. What's less obvious is that they all rely on the same type of memory – relational memory. As the first real content for this blog, I'll be giving a breezy overview of relational memory theory (RMT) intended for a general audience with a minimum of jargon. In future posts, I'll elaborate and offer more specifics. But for now, the basics of relational memory and RMT.

Multiple memories, multiple systems

The earlier examples describe what we often think of as memory – they focus on events, places, and facts. However, we can store information about earlier experiences in lots of different ways, all of which count as memory. Here are a few examples:

• Your significant other is really excited about riding bikes in the park, so despite being years out of practice you saddle up and find yourself gliding along with no effort.
• Your student submitted his report in a bizarre font that you can barely read at first, but by the third or fourth page you're barely noticing it.
• You pull into a surprisingly empty parking lot at work only to realize that it's Saturday and you've followed your daily commute instead of running errands.

In each case there's memory at work even though what’s been learned is a skill or habit. However, memories of this kind seem very different from memories for facts and events.

The distinction between these two kinds of memory is a key component of RMT. The theory suggests that different kinds of memory depend on unique memory systems, and that memory systems belong to one of two groups. Non-relational memory systems are the second type that we considered, and are well-suited for gaining motor skills such as bicycling, tuning perceptual systems to read a difficult font, or habit learning that can lead to commuter's coma.

Non-relational learning is typically very incremental and slow; non-relational memories are usually very durable but inflexible. These are great properties for lots of memories. Having learned to ride a bike, you'll retain that motor skill throughout your life with little or no practice. However, we don't always have time to learn new information by practicing. You may only hear a new acquaintance's name once; you probably won't have the luxury of parking in the same spot every day for a year; and you aren't going to rehearse your daily schedule until you know it by heart. Slow, durable learning is great, but sometimes you need to learn fast.

Relational memory

Relational memory is used every time you need to bind together two or more pieces of information together, especially when those pieces of information were not previously related to each other. Say you're trying to bind Alice's name to Alice's face during your first meeting: there's nothing in her face that can clue you in to the name; and there's nothing about the name that would prompt you to think of a particular face. The relation between these two pieces of information is therefore arbitrary. Non-relational memory systems might eventually help you learn the arbitrary "Alice"-face relationship, but the hundreds of introductions it would take might get on her nerves. Relational memory offers a shortcut – having met Alice once (or twice or three times), you have a decent chance of remembering her name.

Relational memory is strikingly different from non-relational memory, and not just in terms of learning speed. Relational memory is also extremely flexible. Meeting Alice again later on, you might recognize her in a new outfit and a work setting. One lonely bit of information, such as Alice's face, can be enough to trigger memory for all kinds of related information, including her name, the party where you met, and so on. And despite the speed with which relational memories are formed, they can be extremely durable, lasting for years. The strengths of relational memory, its speed and style of learning, complement non-relational memory in important ways.

Where to next?

I'll pause here for now, but plan to write more about RMT before too long. Likely topics:

• RMT in the brain
  • Brain regions supporting relational memory
  • Brain regions supporting non-relational memory
• The continued evolution of RMT
  • Development during my time at UIUC
  • Contributions by other scientists
• My own experience studying RMT
  • Developing RMT tasks
  • Working with amnesic patients
• Challenges for RMT
  • Future directions and how to stay relevant
  • Alternative accounts of memory function

But for now, I'll just close by acknowledging the guys who put it all together.

Origins

All credit for originating RMT belongs to Neal J. Cohen and Howard Eichenbaum. If you're interested in reading an authoritative account, check out their respective publications at the above websites or PubMed, or one of their two books on the topic (non-affiliate links, I promise).