Abstract
This study explores the possibility of using EEG (electroencephalography) in conducting usability tests of hardware products such as DSLR cameras which require physical contact with hands. Since questionnaire-based usability tests use verbal or lingual expressions about tactile feeling, it is often difficult to precisely indicate the level of the differences. Thus this study took a different approach utilizing EEG technology to directly measure psychophysical responses in order to quantitatively observe the difference in tactile sensation. In the experiment, four different brands of camera with similar market position and outfit design were used. Twenty subjects were asked to complete the same three tasks. They included the primary modes of picture taking: gripping, shuttering, and mode dialing. Among EEG parameters, we chose relative alpha band power (7.5-12.5 Hz) and beta band power (13-30 Hz) on the frontal, parietal, and occipital lobes. Subjects were told to perform the tasks twice, once with closed eyes and again with eyes opened. ANOVA and post-hoc analysis were performed to indicate the differences of alpha and beta band power response of subjects during given tasks. In results, relatively apparent differences were observed in mode dialing in left hemisphere and with open eyes than the others. Such data revealed user’s tactile preference among four DSLR cameras although the outcome was not always statistically significant. In conclusion, psychophysical response can be applied to evaluate the subtle tactile stimulation of products along with questionnaire-based tests under certain experimentally-controlled conditions.
Research Goal
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Try to find the way to quantify of Physical User Interface Usability
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By comparing the operation and initial tactile feelings of four products with similar hardware designs with brain waves, I want to determine whether it is possible to distinguish minor differences.
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Based on the EEG data showing significant results, the shape, material, and design characteristics of the product are compared and the design improvement factors and directions are presented
Research Scope
DSLR or mirrorless cameras competing for similar markets and consumer groups is selected as an experiment target to investigate the gripping feeling, shuttering feeling, and dialing feeling.
*All cameras hide the brand name so that it is not known
Gripping
Focus on the feeling of holding the camera with one hand.
Shuttering
Focus on the feeling of pressing a button when taking a picture.
Dialing
Focus on the feeling of turning the camera's mode dial with your finger.
Method
In the experiment, four different brands of camera with similar market position and outfit design were used. Twenty subjects were asked to complete the same three tasks.
Null Hypothesis
H1
When comparing the sense of grip, the difference in tactile feel between cameras cannot be found with brain waves.
H2
When comparing the shutter feel, the difference in tactile feel between cameras cannot be found with brain waves.
H3
When comparing the feel of the dial, the difference in tactile feel between the cameras cannot be found with brain waves.
Experiment Design
Independent variable: Camera
Dependent variable: Relative Alpha Power Spectrum, Relative Beta Power Spectrum
Equipments
Experiment Process
Data Analysis
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Sampling rate: 200Hz
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5-10 seconds of experimental data for 15 seconds, Using the average value of the difference of 3 seconds before and after
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Power Spectrum Analysis (Used software Laxtha):
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Converting time domain data to frequency domain using FFT(Fast Fourier transform),
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Alpha("α": 7.5~12.5Hz), Beta(" β ": 13~30Hz) Amplitude (power, μV2) for each band
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ANOVA, Bonferroni correction
Result
In results, relatively apparent differences were observed in mode dialing in left hemisphere and with open eyes than the others. Such data revealed user’s tactile preference among four DSLR cameras although the outcome was not always statistically significant. In conclusion, psychophysical response can be applied to evaluate the subtle tactile stimulation of products along with questionnaire-based tests under certain experimentally-controlled conditions.
Found of Design Elements
Shutter Depth
Considering the depth of shutter release, the frequency of failure of half-shutter clicks should be reduced and accurate feedback should be provided.
Shutter Position
The shutter position should be designed so that the influence of the shutter to be pressed can be quickly induced, and anatomical factors such as the joint angle of the finger and the palpable area of ​​the palm should be considered.
A
Examples of situations where the shutter position cannot be found immediately
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B, C
Difference between the angle of the index finger and the distance between the hand and camera according to the shutter position