# Electric devices changing brightness - motion detectors? **URL:** \ **Category:** Factual Questions\ **Created:** [December 11, 2020, 2:55pm UTC](https://boards.straightdope.com/t/electric-devices-changing-brightness-motion-detectors/927831 "2020-12-11T14:55:31Z")\ **Posts on this page:** 3\ **Page:** 2
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [December 12, 2020, 10:40am UTC](https://boards.straightdope.com/t/electric-devices-changing-brightness-motion-detectors/927831/21 "2020-12-12T10:40:01Z")
> [@markn\_1](#): > > When your eyes make a saccade (a rapid movement from one point of focus to another), your brain ignores input from the eyes during the movement, to avoid perceiving a disorienting blur. This is called saccadic masking. But then it goes further – at the end of the saccade, it tricks you (or I guess more accurately it tricks itself) into believing that the object it sees at the end of the saccade was actually visible during the entire duration of the saccade. _[and ignoring everything in between]_ So whatever image you see at the end of a saccade appears to have persisted unchanged for up to several hundred milliseconds. This is why so many drivers pull out into the path of cyclists and motorcyclists. They look both ways and totally fail to see them. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [December 12, 2020, 1:09pm UTC](https://boards.straightdope.com/t/electric-devices-changing-brightness-motion-detectors/927831/22 "2020-12-12T13:09:48Z")
The camera will adapt the recording to the light level of the room, so it’ll be difficult to evaluate if the digits brightened or not. He needs to leave the phone in the room recording the digits. If the effect is not noticeable every time he might need something capable of just taking a picture every two seconds (or similar). ---
**Author:** ![GMANCANADA](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gmancanada/32/2837_2.png) [@GMANCANADA](https://boards.straightdope.com/u/GMANCANADA)\ **Post date:** [December 12, 2020, 1:13pm UTC](https://boards.straightdope.com/t/electric-devices-changing-brightness-motion-detectors/927831/23 "2020-12-12T13:13:58Z")
When I did my undergraduate in psychology I took a course on perception. I’m not sure if this is the same phenomenon or simply related, but one of the interesting things I learned was the way human (and other species) vision works is when we stare blankly either near or far (not moving your eyes whatsoever), after 10 or 15 seconds our field of vision basically blends together. If there is then any motion at all in our field of vision our eyes are immediately drawn to it. The context of this was that animals perceptions are designed primarily perceive _changes_ in state. If the same stimulus is given constantly we stop noticing it. The olfactory example being how you don’t smell your own cologne or perfume but others can overwhelmed when they come near you. The professor said a common example of this is how a bird hunts. Their heads and eyes remain perfectly motionless so when any insect moves in their field of vision they immediately spot it. Similarly, prey animals will keep their eyes and heads perfectly still if they think they are being stalked. That allows them to immediately detect where the predator is coming from. I actually do this frequently on hikes in the woods If I think I see an animal in my peripheral vision. It works shockingly well [Previous page](https://boards.straightdope.com/t/electric-devices-changing-brightness-motion-detectors/927831.md?page=1)