Walking EEG Study – Nature vs. Crowds and how it affects us all

  • out-of-lab
  • GSR
  • multimodal
  • neural oscillations
  • synchronization
  • walking

Urban and natural environments have distinct impacts on our cognitive and emotional states. Have you ever felt overwhelmed by traffic noise, billboards, and crowds in a huge city? Or felt a wave of relief at the sight of an empty beach while vacationing?

Exposure to nature, such as parks and forests, has more positive effects on mood and attention compared to urban spaces. Yet there is growing interest in studying effects of environments beyond the nature vs. urban dichotomy.

Mobile EEG allows researchers to investigate emotional experience of walking in indoor and outdoor environments, while also considering the influence of crowding.

Expected outcomes of the study

Authors of this study hypothesize outdoor spaces would give participants a more positive and calm feeling, compared to indoors. We can attribute this to spaciousness, boundary height, or sense of enclosure.

Crowds could have a more unpleasant feel compared to no people. An alternative hypothesis is that pedestrian crowds might be associated with human presence and city life. This could result in positive perception of crowding amongst participants.

Difference in walking EEG and standing while exposed to different environments hasn’t been studied that much. As a result, we don’t know how physical activity affects brain measurements or personal feelings. The last hypothesis in this work is that walking leads to stronger emotional experiences.

Setting up the experiment

To address these questions, the scientists let the participants walk or stand on a treadmill while watching walk-through videos. The researchers measured two types of physiological signals:

EEG, using mobile EEG SMARTING device, and Electrodermal activity (EDA), using Shimmer GSR+.

They synchronized the two data modalities with presented stimuli using Lab Streaming Layer (LSL) protocol.

 

Read more about event triggering and data synchronization in mobile EEG studies with LSL.

Recording walking EEG on treadmill and viewing different environment videos
Physical setup of the walking EEG experiment (left) and the experiment procedure (right)

Researchers wanted to examine effects of different physical and social environments. They presented different environment videos in first-person perspective:

Indoor crowded (IC), outdoor crowded (OC), indoor uncrowded (IU), outdoor uncrowded (OU) and green space (G).

Video stills of Green, urban outdoor and indoor spaces with different levels of crowding
Stills from different environment videos.

After each video, participants self-reported their emotional state using the Self-Assessment Manikin (SAM). They rated their arousal and valence on a scale from 1 to 9.

Also, participant filled a questionnaire about their sense of presence while watching the scenes.

Exploring the data

From EEG data, researchers extracted multiple measures in frequency domain. These measures imply frequency power of EEG in different spectral bands.

With EDA, researchers extracted slower (phasic) and faster (tonic) components.

To check effects of different videos, researchers fitted a Bayesian hierarchical regression model for each measure. Then they performed pairwise contrast analysis in case of types of environments and social density.

Contrast in subjective ratings and physiological measures in case of different environments
Showing difference in parameters in case of green vs urban environments. Walking and standing groups are shown separately.
Contrast in subjective ratings and physiological measures in case of different social densities
Showing difference in parameters in case of crowded vs uncrowded environments. Walking and standing groups are shown separately.

Effect of different environments on self-reported measures

Arousal and valence ratings show that participants felt the most calm and positive while looking at green spaces. When it comes to urban outdoor vs. indoor, participants felt better in outdoor environment.

Lastly, crowding was always perceived as less calming compared to no people. Participants also reported a more negative valence in case of bigger crowds.

Physiological markers – EEG and EDA measures in crowds

Theta/beta power ratio (TBR) is associated with cognitive load. Researchers found that green spaces evoked lower TBR compared to crowded environment. This implies more mind-wandering in nature and less attention control in crowds.

Higher Frontal alpha asymmetry (FAA) indicates more approach affective states. FAA was higher in participants during walking through crowded outdoors compared to green spaces.

Physiological arousal based on EDA is higher in participants exposed to crowds.

These findings all add up to previous studies where researchers suggest even artificial crowds in a virtual setting have influence on our experience.

Physiology in outdoor vs indoor environments

Researchers observed that outdoor spaces produced positive and calm emotions compared to indoors. Both EEG measurements and EDA components back this up.

Walking EEG compared to standing condition

Two groups (walking vs standing) didn’t have different perceptions of spatial presence. Yet, researchers did find difference in physiological data between walking and standing participants.

Looking at FAA in walking EEG, they noticed a more positive affective state when in crowds compared to standing group. Researchers think this has to do with sense of control when walking in a crowd, rather than just standing.

EDA measures show evidence that walking increases physiological arousal, compared to standing group.

To summarize

This study shows the influence of environment type, crowding and walking on subjective experience.

The results suggest that green environments evoke more positive affect than urban spaces. Participants perceived outdoor environments as more positive than indoors.

Uncrowded spaces, compared to crowds, are associated with more calm and positive emotions. Less crowding reduces physiological arousal and lowers attentional demands.

With these results, researchers add to the field of environmental neuroscience. They give us new ideas on how we experience urban environments and different social densities.

Finally, researchers highlight the crucial value of mobile EEG studies. They allow participants to experience environments while recording walking EEG inside the laboratory or ‘in-the-wild’.

 

The original publication source: https://www.nature.com/articles/s41598-022-20649-y#citeas

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