The neutron lifetime has been measured by comparing the decay rate with the reaction rate of $^3$He nuclei of a pulsed neutron beam from the spallation neutron source at the Japan Proton Accelerator Research Complex (J-PARC). The decay rate and the reaction rate were determined by simultaneously detecting electrons from the neutron decay and protons from the $^3$He(n,p)$^3$H reaction using a gas chamber, the working gas of which contains diluted $^3$He. The measured neutron lifetime was $898\,\pm\,10\,_{\rm stat}\,^{+15}_{-18}\,_{\rm sys}\,$s.

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Event-related potentials from visual stimuli that were presented after voluntary actions were recorded to examine how people expect their action effects. Participants pressed a button in response to a cue stimulus (L or R) either in the fixed condition where participants always pressed a center button or in the choice condition where they selectively pressed the corresponding left or right button. Immediately after the button press, a second stimulus (left or right) was presented visually to inform that their action was registered. When the second stimulus did not match the cue stimulus (p=.20), a late positive potential (LPP) with a posterior scalp distribution occurred in a latency range of 500-700 ms. The amplitude of this mismatch-related LPP was larger in the choice condition than in the fixed condition. The results suggest that the cognitive mismatch between the expected and actual action effects is reflected in the LPP, and the selection of a specific action strengthens the expectation of its action effect.

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