The Color and Blink Frequency of LED Notification Lights and Smartphone Users’ Urgency Perception

LED notification lights are used in smartphones to deliver various information to users, such as missed calls, incoming calls, receiving a new text message, and low battery. This study explores whether the settings of the color and blink frequency of the LEDs notification lights affect smartphone users’ urgency perception in two important information states, i.e., missed calls and incoming calls. We set the blink frequency of LED notification lights high and low, assuming that high frequency blink will be perceived as more urgent notification. As for color, we first set the color of LED indicators as White for both high and low blink frequencies. Then, we changed the color to Red for high frequency blink and Green for low frequency blink to examine whether color has any effect on smartphone users’ urgency perception of the notification. We measured users’ urgency perception by asking participants to evaluate how effective each setting of LED notification lights is in indicating the degree of urgency of the corresponding information state. In an experiment with 30 participants, we found that participants perceived high blink frequency as more intuitive and attractive and therefore more effective than low blink frequency in indicating high urgency in both information states. We also found that the use of color increases users’ overall urgency perception. We further found that users’ urgency perception—both intuitive and attentive—was highest when color was used and the blink rate of notification was high. That is, the urgency perception score was highest when the color was Red and the blink frequency was high. In the post-experiment interviews, participants chose red as the best color to indicate urgency. Given that, we conclude that the use of red color with high blink frequency of the LED notification light is most effective in conveying urgency information.