On rats - Emily Anthes in NYT:

‘Mr. Lignier built his own version of a Skinner box — a tall, transparent tower with an attached camera — and released two pet-store rats inside. Whenever the rats pressed the button inside the box, they got a small dose of sugar and the camera snapped their photo. The resulting images were immediately displayed on a screen, where the rats could see them. (“But honestly I don’t think they understood it,” Mr. Lignier said.)

The rodents quickly became enthusiastic button pushers. “They are very clever,” Mr. Lignier said. (He named the white rat, which proved to be the cleverer of the two, Augustin, after himself. The brown and white rat he named Arthur, after his brother.)
But after this training phase, the rewards became more unpredictable. Although the rats were still photographed every time they hit the button, the sweet treats came only once in a while, by design. These kinds of intermittent rewards can be especially powerful, scientists have found, keeping animals glued to their experimental slot machines as they await their next jackpot.
Indeed, in the face of these unpredictable rewards, Augustin and Arthur — the rats — persisted. Sometimes, they ignored the sugar even when it did arrive, Mr. Lignier said, and just kept pressing the button anyway.’

(…)

‘Indeed, social media has been described as “a Skinner Box for the modern human,” doling out periodic, unpredictable rewards — a like, a follow, a promising romantic match — that keep us glued to our phones.
Or maybe being able to keep ourselves busy pressing buttons is its own reward. In a 2014 study, scientists concluded that many human volunteers “preferred to administer electric shocks to themselves instead of being left alone with their thoughts.” Maybe we would rather sit around and push whatever levers are in front of us — even those that might make us feel bad — than sit with ourselves in quiet contemplation.’

Read the article here.

Everything is better than being alone with yourselves. That might be one of the many things human share with rats.

Although based on this article and observations on the streets of New York I would say that rats are probably less vain than humans, in general.