1 . If you’ re reaching for the last piece of pizza at a party, and meanwhile see another hand going for it, your next move probably depends on how you feel and whom the hand belongs to. Your little sister — you might just grab the pizza. Your boss — you probably will give up.

Now researchers have made progress in understanding how mammals’ brain encodes social rank and uses this information to shape behaviors — such as whether to fight for the last pizza slice. They discovered that an area of the brain called the medial prefrontal cortex (mPFC) was responsible for representing social rank in mammals; changes to a mouse’s mPFC affected its dominance behavior. But it was unknown how the mPFC represented this information and which neurons(神经元) were involved in changing dominance behaviour.

In the new study, Professor Kay Tye let groups of four mice share a cage. Some mice became more dominant and others more subordinate. As soon as the mice were paired up, he discovered, the activity of their mPFC neurons could predict — with 90 percent certainty — the rank of their opponent.

“We expected animals might only signal rank when they are in a competition,” says co-researcher Nancy. “But it turns out animals walk around with this representation of social rank all the time.”

When the researchers next asked whether the activity of the mPFC neurons was associated with behaviour, they found something surprising. The brain activity patterns were linked with slight changes in behaviour, such as how fast a mouse moved, and they also could predict — a full 30 seconds before the competition started — which mouse would win the food reward.

The winner was not always the more dominant, but the one engaged in a winning mindset. Just as you might sometimes be in a more competitive mood and be more likely to snatch that pizza slice before your boss, a subordinate mouse might be in a more winning mindset than a more dominant mouse and end up winning.

The areas of the mPFC associated with social rank and winning mindset are next to one another and highly connected. Signals on social rank impact the state of the brain involved in winning mindset. In other words, a subordinate mouse’s confidence and winning mindset may partially decrease when faced with a dominant one.

“This is further evidence to suggest that we are in different brain states when we are with others compared to when we’re alone,” says Tye.

3 . After the movers had taken the furniture and boxes, once the house was empty of everything but dust and echoes, I took from my pocket a(n) _______I had found in the garden several days before. A friend had _______saying goodbye to the house with a special ritual (仪式) of the Memory Stone.

The idea is to take a stone that you like and walk through the house and gardens, projecting your _______onto it. I wasn't sure it would work, but I decided to _______ it. One of the things that _______me about leaving the house was the idea of leaving behind all the memories. Perhaps this offered a way to take _______with me somehow.

I stared downstairs. It was a beautiful day and the light was shining through the windows. At first, the memories didn't come _______. I sat there, staring at the stone, but _______ happened. Just some memories of memories--- _______I had seen in photographs, words I had read in letters and diaries.

But after just a few minutes, that ________. Suddenly, the room was crowded with people I hadn't seen for years, as well as some people I had seen just the day before. It's winter, and we're all in the kitchen, making a(n) ________ for Christmas. It's summer, and we are trying to find ________ from the heat. I'm 11, trying on my new school uniform in front of the ________. My mother is coming upstairs to say good night and give me a hug. I have come in________ for my curfew (宵禁) ；I am tiptoeing up the stairs, hoping I won't ________anybody. My father is dancing with my friend Gideon. Now my father is old and I am sitting close to him on his bed, saying goodbye to him for what would ________ to be the last time.

One moment I found myself ________; and in another, I surprised myself by bursting into laughter. But mostly, the experience was strangely ________.

It's been several months since I walked out of the house for the last time. I don't know ________this stone I have, this piece of the place, can really hold so much. ________, right now, as pick it up and gaze at it, I seem to be back home.