Color and Emotion: Effects of Hue, Saturation, and Brightness
Colour is a fundamental part of human perception. Light from the visible spectrum is absorbed and reflected in varying ways. The eye receives the reflected portion, relays it to the brain through the optic nerve, and processes it in the visual cortex. Given the complexity of this phenomenon, the question arises regarding the various locations where colour is processed in the brain. In this study, authors Kuller, Wilms and Oberfeld (2017) investigate this question. Specifically, they aim to study the impact of chromatic lights on human physiology and emotions. Their endeavour to corroborate the colour-emotion association was substantiated by addressing the shortcomings of previous literature. By independently varying the hue, brightness, and saturation, the authors could control the exact colourimetric specifications and determine the association between these dimensions and human physiology and emotion. In addition, their approach involved measuring the emotions evoked by the colour instead of measuring the valence of the colour itself. This allowed for accurate measurements of emotional state and comparison against physiological measures such as skin conductance and cardiovascular activity.
Three primary measures were taken during the experiment. First, emotions were assessed using a nonverbal Self-Assessment Manikin, where participants rated their current arousal and valence on a 9-point scale. Physiological measures were also recorded for electrodermal activity and heart rate. Electrodermal activity was analyzed using the amplitude and latency of conductance. Each index was significant, as the amplitude described the difference between the baseline and peak of the response and the latency indicated the time difference between the baseline and the stimulus onset.
Sixty-two participants were seated before an LED panel that displayed 27 chromatic colours, a product of three levels of hue (red, blue, green), brightness (dark, medium, bright), and saturation (low, medium, high) and 3 brightness-adjusted achromatic colours, for a total of 30 discrete trials. Each trial involved a 60-second achromatic adaptation phase where participants viewed a white light on the LED panel to prevent the chromatic adaptation of the rod and cone cells in the eye. After this, the colour stimulus was presented for 30 seconds, followed by the emotion rating scale. Once the SAM ratings were submitted, the next trial began immediately.
Following the experiment, data analysis revealed several significant associations and interactions consistent with the proposed hypotheses. Saturation and brightness had a statistically significant and positive impact on self-rated arousal (higher saturation/brightness = increased arousal) with red being reported to be the most arousing hue. However, an important nuance must be noted: hue and brightness positively impacted arousal only when the saturation was high. A similar nuance was also reported in valence ratings. Valence ratings of green and blue increased with saturation while those for red were highest at medium saturation, followed by low and high. Lastly, valence was positively affected by the brightness for all hues and saturations.
Akin to SAM ratings, saturation positively influenced the amplitude of skin conductance rate. However, although positive, the effect of hue on amplitude was not statistically significant. Similarly, the effect of chromatic colours on skin conductance latency produced statistically insignificant results. Interestingly, the authors noted that achromatic colours (with 0% saturation) also generated high skin conductance amplitudes, contradicting their initial hypothesis. The effect of chromatic colours on heart rate was observed as an acceleration due to higher brightness. Although statistically insignificant, this result was consistent with their prediction. The only significant effect on the heart rate was the deceleration caused by the achromatic stimuli. Beyond the proposed goals of the experiment, the authors also found a weak yet positive correlation between the participants’ self-rated arousal and SCR amplitude. Sex differences were virtually non-existent, except for achromatic stimuli where female participants rated gray colours less pleasantly than male participants.
Across all participants, the authors found evidence of a correlation between the three dimensions of colour (hue, saturation, and brightness) and human response. The study's central conclusion emphasizes that psychological or physiological responses are not determined by a single dimension but rather by the combined influence of all three dimensions. Despite its merits, however, the study only examines three hues. Authors suggest examining even more hues could provide greater insight into this context. In addition, using light strictly limits the generalizability of the study’s implications. For instance, this study does not establish any equivalence between the influence of LED lights and oil-based or water-based paint. Using paint as a stimulus instead of light could provide a more nuanced understanding of the relationship between colour and human responses.
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Citation:-
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Wilms, L., Oberfeld, D. Color and emotion: effects of hue, saturation, and brightness. Psychological Research 82, 896–914 (2018). https://doi.org/10.1007/s00426-017-0880-8