Have you ever been at a party full of people and, despite the noise, been able to perfectly follow the conversation with the person in front of you, or heard your name spoken by someone, even if you were immersed in something else? Here, this is it the cocktail party effect and explains how auditory attention is selective and flexible: we don’t listen to everything, but we choose what to listen to. In a certain sense, this is also what is happening to you as you read these lines: surely, if you pay attention to it now, you will hear noises around you; yet your brain had “hidden” them by considering them irrelevant, so as to allow you to concentrate only on reading. Wanting to be more precise, this last example explains how ours works in general selective attentionwhich filters out any non-significant stimuli to prioritize what matters at a given moment. THE’selective listening (or cocktail party), is specific to sound sources.
The cocktail party effect, what it is and why it is called that
The study of the cocktail party effect was born in the 1950s thanks to the British psychologist Colin Cherry. To understand how auditory attention worked, he devised an experiment known as dichotic listeningor dichotomous listening.
Participants were made to wear headphones that played two different sound messages at the same time: one in the right ear, another in the left. Furthermore, they were asked to concentrate on one of the two messages (“expected channel”) and to repeat it out loud, word for word, completely ignoring the other (“unexpected channel”). What emerged from the experiment was that people were able to remember almost all of the message they were focused on, while nothing (or almost nothing) of the other message. In fact, when they were later questioned about the content of the unexpected message, the participants showed that they had grasped very few details: they had not noticed whether the language had changed, whether the words were reproduced backwards or whether the message was nonsense. However, Cherry observed that the subjects perceived some physical characteristics of the unexpected messagesuch as a change in voice (for example, from male to female) or the insertion of a pure tone.
Subsequent studies have also highlighted an exception to this selective filter: the people they tended to notice their own name if it was spoken in the unexpected channel. This proves that the brain continues to monitor even the information it deems less important, intervening when it detects something particularly significant on a subjective level. It does not limit itself to excluding unwanted stimuli: it keeps them in a sort of “passive listening zone”, ready to bring them to the foreground if they become relevant.
The two principles underlying the cocktail party effect are therefore:
- the selectivity of attentionor the ability of our mind to concentrate cognitive resources on specific stimuli, ignoring others; this selectivity depends on the fact that our brain is programmed not to overload itself and only selects what it deems useful or important at a given moment;
- the relevance factor: the cocktail party effect manifests itself especially when the stimulus that captures our attention is highly relevant to us, attributing it to it a cognitive priority. Furthermore, the ability to switch attention from one relevant sound to another (for example when we hear our name pronounced while we are absorbed in something completely different), depends a lot on the significance which represents every sound source for us. Some factors that may capture our attention include information regarding our safety, the possibility of a reward, or even topics that reflect our personal interests or current concerns. For example, a parent may be immediately attracted to the crying of his baby, even if far away and covered by other noises.
The cocktail party effect is therefore the ability that our brain has to focus on a single sound source in a noisy environment, filtering and suppressing auditory inputs deemed irrelevant at that moment; at the same time, the brain continues to monitor what is happening around us and can get our attention if it perceives significant stimuli (such as our name, a familiar voice or a topic that interests us).
How selective attention works and what happens in our brain
Modern neuroscience has shown that the cocktail party effect is the result of a refined network of attentional processes. The auditory cortex continuously receives auditory inputs from any direction and of any intensity, but only some are chosen and amplified by the areas responsible forselective attention. It is as if the brain applies a “dynamic filter” that is constantly updated, based on what it deems important, interesting or significant.
Even when we are concentrated in a single conversation, however, the auditory areas continue to monitor the environment in the background; and this is precisely how we can catch a sudden sound, a familiar voice or our name, even if we weren’t paying attention. However, this filter is not foolproof; when we are tired, stressed, or overloaded with too much information, our ability to deploy selective attention and consequently also selective listening decreases: this is the reason why we sometimes struggle to concentrate in noisy environments or while “multitasking”.
The cocktail party effect is a fundamental part of how we function: every day our mind selects, filters, prioritizes what matters. And to think that the way in which our brain is able to isolate or recognize a voice among the noise has become a model for the development of speech recognition and artificial intelligence algorithms. When we talk to a voice assistant like Alexa or Siri in a noisy environment, the system faces the same problem studied by Cherry: distinguish the user’s voice from all other sound sources and at the same time suppress background noisejust like when our brain listens to a single person at a party.
