Rhodopsin just like a photomultiplier detector has a certain noise level. The rate of noise counts decreases with temperature - so you would expect the performance of a person at this task to improve as you cooled their body.
This was actually done for toads. The experimenter would train a toad to lash its tongue at faint flashes of light and the performance of the toad at discriminating light from no light was measured as the toad's body temperature was cooled. As the toad was chilled the quality of its guesses improved. Interestingly it's error rate as a function of temperature matched the change in signal to noise ratio for the currents in the retinal cells. Bizzare! The toad's brain controlled it's tongue at the threshold of being able to statistically distinguish signal from noise.
Unfortunately this idea is impractical for warm-blooded creatures, whose body temperature is strictly regulated... at least until it isn't, at which point they're no longer much good for seeing photons because they're busy being treated for hypothermia.
Although I'm sure that Rutherford and Geiger, or their grad students, were quite happy to avoid the necessity of performing their human photomultiplier experiments while sitting in a chilled room.
This was actually done for toads. The experimenter would train a toad to lash its tongue at faint flashes of light and the performance of the toad at discriminating light from no light was measured as the toad's body temperature was cooled. As the toad was chilled the quality of its guesses improved. Interestingly it's error rate as a function of temperature matched the change in signal to noise ratio for the currents in the retinal cells. Bizzare! The toad's brain controlled it's tongue at the threshold of being able to statistically distinguish signal from noise.