This technology relates to an image capturing element and drive method, and an electronic device, with which drive can be effected stably using a low voltage and with low power consumption, and with which it is possible to ensure adequate time resolution during detection. An optical detector is provided with a pixel array unit including a plurality of first pixels and a second pixel. The first pixels each include a photoelectric conversion portion which subjects incident light to photoelectric conversion, a floating diffusion portion which generates a voltage corresponding to the amount of charge obtained by means of the photoelectric conversion, and a transfer portion which transfers charge from the photoelectric conversion portion to the floating diffusion portion. A signal is read out intermittently from each first pixel. Further, the output from the second pixel is continuously monitored to detect the incidence of light. This technology is applicable to radiation counters.