Why didn’t Sherlock see the glass? 

 (Sherlock meta by sherlock-addict)

There’s been a lot of bantering about how it could be possible that Sherlock didn’t notice there was no glass in Eurus’ cell, so I thought I’d have to try to explain this fact to you.

Have you ever been really stressed? Do you know what happens to your brain when you are confronted with a really stressful situation?

Your cognitive abilities shrink, your vision field is limited to the point in which you can get your vision tunneled.

All your senses can become tunneled when you are stressed. For vision, it means your visual attention can be focused on one small geographic area of an emergency scene or one task being performed at a scene and you miss seeing things in your periphery.

When you are suffering from tunneled senses your situational awareness is vulnerable because you are likely to miss important clues and cues.

No wonder, even for such an observant person as Sherlock, that in those extremely stressful circumcstances - seeing his long forgotten, psychopatic sister, after he heard (and ignored) “vatican cameos” from John, he lost his usual abilities to see details, he was doing his best but it was his humanity, normal physiological and emotional reactions that didn’t allow him to use his brain to its fullest, as usual.

I am really not surprised Sherlock didn’t see there was nothing to see.