# Question about tutorial demo

**URL:** <https://psychtoolbox.discourse.group/t/question-about-tutorial-demo/3942>\
**Category:** Programming Help\
**Created:** [August 1, 2021, 1:27pm UTC](https://psychtoolbox.discourse.group/t/question-about-tutorial-demo/3942 "2021-08-01T13:27:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![makis6](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@makis6](https://psychtoolbox.discourse.group/u/makis6)\
**Post date:** [August 1, 2021, 1:27pm UTC](https://psychtoolbox.discourse.group/t/question-about-tutorial-demo/3942/1 "2021-08-01T13:27:29Z")

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Hi all

I am using a macbook pro, Big Sur and an external Samsung monitor.

I am learning about PTB-3 by reading the demos. However, I have found an unexpected behavior when running the following demo: [WaitFramesDemo](http://peterscarfe.com/waitframesdemo.html)

Everything seems to work i.e. the screen color (monitor screen, not main screen) changes every `vbl + (waitframes - 0.5) * ifi)` seconds.

The problem is that I cannot stop the experiment. I tried to click on any key of my keyboard (MacBook keyboard) but no luck. So, `KbCheck` never becomes 1.

Why is that? Can I explicitly say to `KbCheck` to “monitor” for input my macbook keyboard?  
For now, it seems that when I click on any key on my keyboard, the keys appear in MatLab’s command window…so the external monitor is “disconnected” from my keyboard.

Thanks

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**Author:** ![dcnieho](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@dcnieho](https://psychtoolbox.discourse.group/u/dcnieho)\
**Post date:** [August 1, 2021, 3:11pm UTC](https://psychtoolbox.discourse.group/t/question-about-tutorial-demo/3942/2 "2021-08-01T15:11:43Z")

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this likely has something to do with the mac os security features (or whatever its called exactly), search this forum as its come up a few times before, also recently