By applying a series of trigger-hair stimulations, the touch hormone jasmonic acid signaling pathway is activated already after the second stimulus. More than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases. The motor cells that close the leafy trap when they received two signals within about 20 seconds. The trap is remembering the first signal for a 20 seconds, and then the first electrical pulse is forgotten, resetting the trapping process. (Böhm et al. Current Biology, Available online: 21 January 2016).
http://www.nytimes.com/2016/02/02/science/the-venus-flytrap-a-plant-that-can-count.html