The history of most human gestures is never written down, precisely because it is something we learn before literacy or memory and thus something we take entirely for granted.
Rebecca MorelleScience Editor
，推荐阅读WPS官方版本下载获取更多信息
缺点：负区间可能“死亡”，即神经元永远不激活
If you're looking for more puzzles, Mashable's got games now! Check out our games hub for Mahjong, Sudoku, free crossword, and more.