Achild notices that, after he is tucked into bed at night and the light is turned off, he can't see much of anything. but if he keeps his eyes open, over time he can see his toys scattered around the room. he doesn't know it, but this dark adaptation comes about because of the

This dark adaption is possible, because of the eyes ability to adjust to different light levels. Allowing him to see better a short period after the lights have been turned off.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

its d i know cause i've been googling it