When you are having a conversation with someone, do you ever want to say a specific word, but for some reason, you cannot find it? You know that word, you can even picture it in your mind or you know its first letter, but still, you don’t manage to say it. Have you ever wondered why you can’t find that word and what happens in your brain while you’re desperately searching for it?

The processes behind saying a word 

This frustrating situation is also known as the tip-of-the-tongue phenomenon and it is a common experience for people all over the world. In order to understand what goes wrong during the tip-of-the-tongue, we first need to know which processes are behind saying a simple word. The words that we know are stored in our memory and for instance, when we want to say the word house, we first think about the concept of the house just like picturing it in our mind. After that, we connect the concept with the word in the language we speak, house in English, then we select the right sounds to pronounce the word (what scientists call phonological information), and only then, we finally say the word. Considering that all these processes are needed to say one single word, it is quite hard to know which type of information is missing during the tip-of-the-tongue. Is it the word itself or is it how we pronounce it in our language?

The missing information during the tip-of-the-tongue

Scientists think that the tip-of-the-tongue state is caused by a problem in retrieving the sounds to pronounce the word from our memory. This theory is supported by the fact that retrieving phonological information from memory gets more difficult with aging and the tip-of-the-tongue occurs more frequently as we get older. In addition to this, scientists suggest that the feeling of knowing the word, that we experience during these episodes, comes from the fact that we already know (at least partly) the meaning of the word and the letters that are part of it. What did scientists do in order to prove this theory? They looked at the brain! Namely, specific regions of the brain are active during specific cognitive functions, such as speaking, making decisions, remembering information, and so on. By looking at the regions that are active during the tip-of-the-tongue, scientists tried to understand which cognitive processes are happening while we are looking for the missing word. 

How to study the tip-of-the-tongue

But how can scientists make sure that participants experience many tip-of-the-tongue states while recording their brain activity? Important to know is that the tip-of-the-tongue happens more frequently with proper names, for instance, we might remember the face and the clothes of a person, but we cannot remember their name. For this reason, in order to study the tip-of-the-tongue, scientists ask participants a set of questions with a person’s name (for example ‘Who painted the ‘Girl with a Pearl Earring’?’) and participants have to remember and say the name (Johannes Vermeer). Another task that can be used is showing a picture of a famous person to participants and asking them to name the person. During these types of tasks, participants can either answer the question/say the person’s name when they know it or they can tell the experimenter that they have a tip-of-the-tongue when they know the person, but cannot remember their name. These tasks can be performed while participants lie or sit in a scanner, which records brain activity and tells scientists which regions of the brain are active in a specific moment. 

The tip-of-the-tongue in the brain 

The areas active during the tip-of-the-tongue experience are located on the left side of the brain, over the frontal (highlighted in purple ), and the lower lateral part of the temporal lobe (highlighted in red ).

 The tip-of-the-tongue in the brain
Using these tasks, scientists found that many regions are active in the brain when participants are experiencing a tip-of-the-tongue: these regions are located on the left side of the brain, over the frontal (area highlighted in purple in the picture) and lower lateral side (area highlighted in red in the picture), part of the temporal lobe. Why are these regions specifically active? The frontal regions take part in the retrieval of information from memory and some temporal regions are involved in phonological processing (finding the sounds to pronounce a word) and in word selection. What does this mean? Many regions are active during the tip-of-the-tongue state probably because this is an effortful process. We might use different strategies in order to try to find the word. On one hand, we might activate regions that are specific for phonological processing, in order to retrieve the sounds to pronounce the word from our memory. On the other hand, we might keep regions that are selective for concept and word information active until we find and say the word. 

Overall, the tip-of-the-tongue phenomenon is a well-known situation in which we struggle to find a word, although we feel like we know it. Thanks to science, we know that this happens because some information about the word is missing, such as the sounds to pronounce it. Some regions on the left frontal and temporal side of our brain are active during the tip-of-the-tongue with the goal of 1) searching and remembering the meaning of the word and its letters and 2) retrieving the missing sound information of the word from our memory. Thanks to the joint activation of these regions, we eventually manage to find the words lost on the tip of our tongue!

This blog was written by Sara Mazzini, Ph.D. Student at the Max Planck Institute for Psycholinguistics.