New Study Challenges the Influence of Color on Temperature Perception

In this newly published study in Scientific Reports (https://www.nature.com/articles/s41598-024-71784-7), we tested the validity of the hue-heat effect in relation to human thermal sensitivity. The so-called “hue-heat effect” refers to the automatic association we make between warm colours, such as red and orange, and warm temperatures, and between cool colours, like blue and green, and cold temperatures.

Several researchers, particularly in the field of thermal comfort, have explored whether this effect has practical applications in everyday contexts. For example, studies have examined whether using warm lighting in an office can make people feel comfortable in cooler environments. However, this body of literature often relies on subjective measures, such as 5 or 7-point scales to assess comfort levels, and the findings across different studies often conflict. To address this, our research group aimed to test the validity of the hue-heat effect using a more objective measure of thermal sensitivity rather than relying on thermal comfort.

We adopted the same experimental paradigm as in our previous published study (https://www.nature.com/articles/s41598-023-47880-5), where participants experienced different temperatures by moving between the Small Cubes.

In the present study, we added a visual stimulus—red or blue light inside the chambers—in synchrony with the thermal stimulus. Specifically, participants moved between the four small cubes, each time indicating whether the second chamber they entered felt warmer or cooler than the previous one. The temperatures in the chambers fluctuated within a range of 23 °C to 25 °C, and the chambers were illuminated with either blue or red LEDs in a manner that was either congruent or incongruent with the temperature. In the congruent condition, the warmer chamber was lit with red lights, and the cooler chamber with blue lights, aligning with the hue-heat effect. In the incongruent condition, however, the warmer chamber had blue lights, while the cooler one had red lights, opposing the hue-heat effect.

© Eurac Research | Andrea De Giovanni

This study also posed a technical challenge for our engineers. Beyond fine-tuning the chambers’ heating and cooling systems to meet the temperature requirements, they developed a feature that allowed the automatic adjustment of the lighting based on the room temperatures being compared, according to the researchers’ requests. This automation ensured that the congruent and incongruent conditions were tested without human error, preserving the integrity of data collection.

Our hypothesis was that participants would demonstrate greater sensitivity—and thus a more precise ability to detect temperature differences—in the congruent condition compared to the incongruent one. However, we found no significant difference between the two conditions. Instead, there was an overall decline in participants’ performance compared to our previous study, where the lights were neutral (all white). This general reduction in thermal sensitivity when the visual stimulus (red and blue lights) was introduced led us to conclude that rather than facilitating or interfering with performance based on congruency, the visual stimulus generally distracted participants.

We hypothesise that the addition of the visual element increased the cognitive load required to perform the task, resulting in diminished thermal sensitivity, which was optimal in the white light condition.

In conclusion, our study suggests that while we may automatically associate warm colours with warmth and cool colours with cold, this association does not appear to influence our thermal sensitivity, raising questions about its practical applicability in real-world settings.

This study is part of the “Cognition Out of the Lab” project, where our researchers explore human sensitivity to environmental temperature and its impact on other aspects of perception.