The fallacy of WhatsApp’s “last seen” status

Last Seen = Fast Response?

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When sending a message with WhatsApp, senders often check the receivers “last seen” status to judge whether the message will be read soon. It shows when the receiver had last openend the application.

it gives me a timeframe and allows me to estimate when my message will be read

Intuitively, if the receiver was online only recently, s/he is likely to be near the phone and see the message soon.

However, results from our recent study on predicting how fast people attend to message notifications indicates that “last seen” is almost as weak as a random guess.

How fast people view WhatsApp messages

We installed an app on the phones of 24 volunteers, which logged, amongst other things, each time that

  • WhatsApp is opened or closed,
  • a WhatsApp message is received, and
  • the user sees the WhatsApp message, either in the notification drawer or in the app

For these volunteers, the median delay between receiving and seeing a WhatsApp was 7.81 minutes, i.e. half of the messages were viewed within 7.81 minutes and the other half later.

We used this time to split the data set into two parts: fast = seen within 7.81 min, slow = seen after 7.81 min. This means, a random guess whether a users sees then message fast or slow has a chance of 50% to be correct.

Not much better than random guess

Next, we used the log data to train a state-of-the-art machine-learning model. We checked how well “last seen” allows it to predict whether the message is seen fast or slow.

It turned out that the prediction was correct in 58.8% of the cases — only 8.8% better than the random guess.

Do not overly rely on “last seen”

Of course, this study has its limitations. The 24 volunteers were in their late twenties and early thirties. Other demographics might exhibit different behavior.

However, the results indicate that we should not overly rely on “last seen” when we want to estimate the availability of our friends.

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