Sorry for the late reply: Response times and reciprocity in WhatsApp and Instagram chats

A new study published on arXiv analyzed 3.4 million messages from 889 donated WhatsApp and Instagram chats to explore how response times reflect reciprocity. The researchers found that about 70% of WhatsApp messages and 44% of Instagram messages were answered within five minutes, confirming the fast-paced nature of instant messaging. More importantly, chat partners showed strikingly similar response speed distributions — captured by Jensen-Shannon distance and regression slopes of 0.786 (WhatsApp) and 0.796 (Instagram) linking one person's probability of replying quickly to their partner's. This balance remained stable over months, suggesting that response timing is a persistent, measurable aspect of social bonding.

Beyond the raw numbers, the study offers a new lens for analyzing relationship dynamics in computer-mediated communication. The authors propose using response speed balance as a complementary metric to track strengthening or weakening social ties — potentially useful for researchers studying online social networks, platform designers aiming to foster healthy communities, or even individuals reflecting on their own chat habits. The data and code are publicly available for qualified researchers, opening the door for replication and deeper exploration of how timing shapes digital relationships.