What makes something memorable?


by Dr. Joni Wallis

As educators, we’re constantly striving to make our message memorable. But what is a memory and what does it look like in the brain? To answer that question, we need to know a little bit about how brains work.

Our brains are made up of neurons. There are other types of cells in there too, but it’s the neurons that are doing the heavy lifting when it comes to creating our mental processes. Let’s take a closer look at those neurons. The picture above shows a neuron that has had a fluorescent dye injected into it so that we can see the whole cell. The first thing we notice is the crazy tangle of branches that come out of the neuron’s cell body. Look a bit closer though, and you’ll see that the branches have dots all along their length. Each of those dots is a synapse and it’s a docking point where other neurons can connect. We have about a billion neurons in our brain and each neuron can connect with about 10,000 other neurons, so there are about 10 trillion synapses in the brain. Making all these connections gets pretty messy. The tangle of wires behind your TV has nothing on the tangle of wires in your brain. The picture below shows a ‘brainbow’: it’s how things look when we inject different colored dyes into all the neurons.

brainbowAll of those messy wires though allow us to make connections between different kinds of information. It’s at these synapses that we store information. Let’s take a concrete example. Imagine an infant eating a strawberry for the first time. When the child sees the strawberry some neurons in its brain will fire that respond to small, red objects. We’ll call them ‘strawberry neurons’. When they bite down into the strawberry other neurons will fire that respond to sweet tastes. Whenever two neurons are firing at the same time, synapses form between them. So the next time the child sees a strawberry, the strawberry neurons will excite the sweet neurons that they newly connect with, and the child will remember that strawberries taste sweet.

Now we know how memories are formed, let’s explore some of the ways we can make those memories stronger. In our strawberry example, we were looking at just a single connection: the association between the sight of a strawberry and its taste. But in reality, memories involve many associations. Think about going out for a meal in a restaurant. A whole bunch of different kinds of neurons will be firing in your brain: visual neurons responding to the faces of your friends, taste and smell neurons responding to the food, auditory neurons responding to voices, and emotional and cognitive neurons responding to the conversation. All of these neurons will be forming synapses with one another and laying down the memory of the evening. However, unlike our strawberry example, where just a single synapse was formed, we now have a big network of synapses, and activating any single neuron in the network can cause the whole memory to be reactivated. Seeing the same friends again, or thinking about the same topics of conversation, eating the same food or attending the same restaurant can all lead to the entire memory being remembered. So for something to be easily recalled, we want it forming as many synapses as possible between neurons and for those synapses to be nice and strong.

How can we make this happen? The first thing we can do is to try to ensure as many neurons are active as possible. That increases our chances that some of them can form connections. So a picture is easier to recall than text, and a movie is easier to recall than a picture. Neurons particularly like novelty, and will fire more strongly to things they aren’t expecting. For example, we’re more likely to remember the pink polar bear than the white one. Second, we can try and capitalize on existing networks. If we’re learning something brand new, although our neurons are firing (because its novel), it’s difficult for them to form any connections, because there are no other neurons firing. However, as we begin to acquire more information about a topic, our network of connected neurons begins to grow, and new information can be readily slotted into the network. So a mechanic is more likely to retain information about a new camshaft than a chef, while the chef will remember a new recipe better than the mechanic. Third, neurons are under the control of our emotions. A brain area called the amygdala acts like a volume control on our neurons, turning up their activity when we’re experiencing an emotion and making it more likely that connections will be formed. This is why we remember emotional events better. It’s a powerful tool that has to be used with care. Extreme emotions can produce “flashbulb memories”, memories so strong and vivid it is almost as though we’ve taken a picture (many of us have flashbulb memories related to hearing about the events of 9/11).

Putting all of this together, we get an insight into why using real world data is compelling and engaging. Real world data is usually richer and more vivid than hypothetical examples. It can also capitalize on the things that children already find rewarding such as sports, video games and movies and use those pre-existing networks of knowledge to teach them new concepts and information. This engages their attention, but also enables them to slot the new piece of information into their pre-existing network and retain it better. Finally, by using information that the children relate to, learning becomes more fun and their reward and emotion circuits can help stamp the memory more strongly into brain networks.

Joni Wallis is a Professor at the University of California, Berkeley in the Department of Psychology and the Helen Wills Neuroscience Institute. She specializes in behavioral neuroscience, cognition, brain and behavior. Joni received a Ph.D. in Anatomy from the University of Cambridge, and did her postdoctoral work in the lab of Dr. Earl Miller at the Massachusetts Institute of Technology.