An external sound or touch can awaken someone.

Can a light? It would have to be very strong, but part of the reason might be that it would have to penetrate the eyelids.

And can a smell or taste?

When we are awake, the impact of sensory stimuli and of changes in them depend on which sense is stimulated.

My question concerns the kind and strength of impact the stimulation of each sense has when we are asleep, in relation to what is needed to wake us up.


Thanks to @Mithoron for linking to another question, asked on this website by @Taladris. That question is certainly quite similar to this one and its answer contains some relevant material, even if the answer is not of high quality because of course our senses are "dimmed" when we are asleep and of course it is not true that "that we respond to our own names in a similar fashion in sleep and in wakefulness". The present question asks specifically about awakening because of sensory input. I believe I am sometimes awakened by smells, although it is hard for me to tell whether or not I am right. Part of my question asks for views or facts concerning whether people can be woken by smells at all. This is different from asking whether we can smell when we are asleep.

  • $\begingroup$ possible duplicate of What senses are active while sleeping? $\endgroup$
    – Mithoron
    May 24, 2015 at 12:00
  • 1
    $\begingroup$ This is not a duplicate in my opinion, as anongoodnurse's answer on the linked question doesn't address vision. $\endgroup$
    – AliceD
    May 24, 2015 at 12:46
  • $\begingroup$ Can someone please remove the box saying "This question may already have an answer here". I have now edited to explain why this question is different. $\endgroup$
    – h34
    May 25, 2015 at 20:46


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