The human brain nonconsciously filters out negative spoken words when distracted

A new study suggests that people are more likely to consciously notice neutral spoken words than negative ones when distracted by a visual task. These findings, published in the journal Psychological Science, provide evidence that the human brain might filter out distracting emotional sounds before they reach conscious awareness. This research helps explain how the mind manages the overwhelming amount of auditory information encountered daily.

Our sensory environment is filled with constant sights and sounds. Because human attention is limited, the brain must prioritize which pieces of information enter our conscious awareness. Conscious awareness refers to the things we actively notice and can report experiencing.

Much of the sensory input we encounter is managed by nonconscious processes occurring behind the scenes. Past research exploring how the brain selects information for conscious processing has largely focused on vision. In these visual studies, scientists often briefly flash images that participants are unable to consciously report seeing.

Hearing presents a uniquely challenging case because humans cannot simply close their ears or avert their gaze from an unwanted sound. Speech is particularly difficult to study because spoken words, unlike images, cannot be delivered in a split second. Because auditory input is constantly flowing into the brain, the cognitive system needs an efficient way to sort important sounds from irrelevant background noise.

The authors of the current study wanted to understand how the emotional tone of a spoken word affects its chances of being consciously heard. Emotional valence refers to whether a stimulus is perceived as positive, negative, or neutral. Insights into this process could explain how nonconscious information influences an individual’s thoughts, feelings, and behavior.

Prior psychological frameworks suggest that detecting negative emotional information is important for survival. Recognizing a threat quickly allows people to react and adapt to dangerous situations. Based on this idea, one might expect the brain to prioritize negative words so they are noticed more easily.

“We assumed initially that people would notice the negative stuff more because that is our conscious intuition,” said lead author Gal R. Chen, a doctoral candidate in psychology at the Hebrew University of Jerusalem. “There is a lot of data showing that when you see or hear something negative you slow down or make more mistakes.”

On the other hand, another psychological perspective suggests that adaptive behavior benefits from filtering out negative information. If a negative sound is irrelevant to a person’s current goals, noticing it might unnecessarily distract them and interfere with their performance. The researchers designed a series of experiments to test whether nonconscious mental processes prioritize or ignore negative spoken words compared to neutral ones.

“Most theories predict that emotionally negative information should receive priority because it may signal threats,” Chen said. “Instead, we found that the mind may sometimes filter out emotionally costly information before we become aware of it. Think about a bus driver who needs to ignore a passenger who angrily speaks on their phone; not hearing the negative information, and stopping to process it, may be beneficial.”

To answer this question, the scientists developed a research method that mimics the phenomenon of inattentional deafness. Inattentional deafness occurs when people completely fail to hear an audible sound because their attention is focused on a demanding visual task. Creating this scenario in a laboratory allowed the authors to observe which types of words break through the distraction and reach conscious awareness.

The researchers conducted three separate experiments involving a total of 101 adult native Hebrew speakers. Participants were instructed to complete a visual memory activity on a computer screen. This visual activity involved looking at images of fictional, purple figures known as “Greebles” appearing in different environments.

In the first two experiments, participants completed a highly demanding memory task. They had to indicate whether the currently displayed figure was identical to the one shown immediately before it. This required continuous, intense focus on the computer screen.

While the participants performed this visual task, a steady stream of auditory sounds played through loudspeakers. Most of these sounds were pseudowords, which are pronounceable combinations of syllables that have no actual meaning in the Hebrew language. The pseudowords were played alongside quiet background chatter to prevent the sudden start of a sound from capturing the participants’ attention.

Occasionally, the audio stream would replace a meaningless pseudoword with a real, meaningful Hebrew word. These real words were selected to be either emotionally neutral, such as the word for cube or phone, or emotionally negative, such as the word for sadness or prisoner. The audio was entirely audible and easy to understand.

After a target word played, the visual task briefly stopped so the researchers could measure the participants’ awareness of the sound. Participants first completed a subjective awareness test by rating whether they heard a meaningful word or only meaningless syllables. Next, they completed an objective test by attempting to identify the category of the hidden word from a set of multiple-choice options.

The first experiment included 29 participants who encountered 72 different target words over several testing blocks. The researchers found that participants missed a significant portion of the real words entirely, confirming that the visual task successfully distracted them. When analyzing the words that were noticed, the scientists noted a specific pattern based on the emotional tone of the sounds.

Participants consistently demonstrated a higher probability of consciously detecting neutral words compared to negative words. This pattern held true even when the researchers accounted for other factors like the arousal level of the words or how distinctively they were pronounced. This finding contradicts the idea that negative information automatically captures human attention.

“This study is a nice example of how our conscious intuitions regarding what we notice are not always what our unconscious is doing,” Chen said. The unexpected pattern initially prompted the research team to question their own data.

“We thought it was a mistake,” Chen said. “So we repeated the study while adding new words. The results gave us the same trend: People notice negative words less.”

The second experiment included 28 participants and served as a replication with a slightly expanded set of 75 words. The authors once again found an overall tendency for participants to consciously detect neutral words more frequently than negative ones. To ensure that the acoustic properties of the sounds were not skewing the results, the scientists used an artificial intelligence tool to analyze the speech patterns.

This computational analysis allowed the team to control for specific linguistic features, such as the number of vowels or the types of consonant sounds in each word. Even after accounting for these acoustic characteristics, the emotional tone of the word remained a strong predictor of conscious detection. Negative words consistently failed to reach awareness as often as neutral words.

The third experiment included 44 participants and introduced a variation in the difficulty of the visual task. The researchers wanted to see if the rate of noticing negative words would change if the primary task was easier and required less mental energy. Participants completed the original, demanding memory task for half of the experiment and a simpler visual task for the other half.

In the simpler task, participants only had to indicate whether the fictional figure on the screen was right-side up or upside down. As expected, participants performed much better and responded faster during the easier task. However, the emotional tone of the spoken words still influenced their conscious awareness in the exact same way.

Neutral words were detected more often than negative words across both the hard and easy visual tasks. The level of cognitive load did not change how the brain prioritized the auditory information. This suggests that the nonconscious filtering of negative speech is a consistent process that occurs regardless of how intensely a person is focusing on something else.

“It may be the default of the unconscious mind to suppress information that may be harmful to us,” Chen said. “If your primary task is to talk to me, random words popping up are not helpful. And if these words slow you down, the default unconscious bias might be, ‘don’t bring them around.’”

While these findings provide new insights into auditory processing, the researchers acknowledge some potential limitations. One concern involves the timing of the awareness questions. Because the researchers waited a brief moment after the word played to ask the participants what they heard, it is possible that the emotional tone of the word influenced short-term memory rather than initial awareness.

If this is the case, participants might have consciously heard the negative words but immediately forgotten them before they could report the experience. Even if the effect is related to rapid forgetting, it still indicates that the emotional meaning of a word drastically alters a person’s ability to report hearing it. Another limitation is that the study only examined negative and neutral single words.

The data provides no information about how the brain might process highly positive words or socially taboo words in a similar situation. Future research could explore whether the same effects appear in full sentences, stories, and more realistic listening environments. Additionally, because the experiments only involved young Hebrew speakers, further research is needed to see if these patterns generalize to older populations or speakers of different languages.

The findings also offer new avenues for studying mental health conditions, such as phobias or PTSD. Chen speculates that future research could investigate whether this unconscious filtering process operates differently in people with anxiety disorders. “The normal population notices negative words less often compared to neutral words,” Chen said. “In a clinical population, they might not have this selection bias.”

By continuing to study how the mind prioritizes sounds, scientists hope to better understand how sensory gating mechanisms affect daily life. “If you think of the unconscious as a gatekeeper guarding us against things that may harm us or influence our decisions, you might ask what happens if this gatekeeper screws up,” Chen added.

The study, “Conscious Detection of Spoken Words Depends on Their Valence,” was authored by Gal R. Chen, Zaheera Maswadeh, Leon Deouell, and Ran R. Hassin.