[SOUND] [MUSIC]. Okay, before we concentrate on vision and hearing, let's just understand what, what's the landscape of perceptions? Are there five? That is a common thing that's taught at least in the United States. well, no, there're not five, there're many more. So, these are the five that are usually talked about, vision, hearing, smell, taste, and touch. And to that we can right off the bat add the vestibulars to that sense. [BLANK_AUDIO] Where we are in space. But in addition, there's another thing that is important, and that is that each one of these, and we'll take the example of of touch. Actually, has several what we call modalities. [BLANK_AUDIO] [COUGH] And so the modalities in the somantic sensory system, are light touch. We can actually feel hair bending. [BLANK_AUDIO] Hair bending. We could feel vibration. [BLANK_AUDIO] We can feel cool and warm and we can perceive, we can a sti, a noxious stimulus can cause pain, which can be aching or stabbing, or shooting, etcetera. So many varieties of that. So, there're many modalities and, and a similar thing can be said for instance, vision. We have a a low light intensity vision, which is good at for sensitivity, and for motion. And we have color vision, etcetera. [BLANK_AUDIO] And one other way to think about this, is that these are the modalities, this is how the, the nervous system divides up these various, systems, but what do we perceive, what do we actually work with? Well, for instance, let's think about eating. In a, in the case of, eating something, we actually use these three, and to make up flavor. So flavor is a little bit of taste, maybe 10% or something like that. It's maybe 70% smell, but it's also highly influenced by touch. Not by touch so much as by not vibration ,sorry, temperature. So it's temperature and texture. [BLANK_AUDIO]. Temperature and texture. Food can ha, taste well, taste and smell good, but have a bad temperature. It can have a bad texture. One that somebody doesn't like. So we, we make compound sensations that use these various systems. Another example of a compound sensation is touch, plus cold gives us wet, and if we, if we don't have those two, we can't detect wet and you can test this for yourself. If you have a non-hairy part to your body, put that put your hand into room temp or body temperature water, and you won't be able to detect that it's wet. Unless it's cold and unless it moves the hairs on your, on your body. So, this, for this reason swimmers who competitive swimmers who shave, when they get into a warm pool, they don't particularly know where the the water begins and ends. In any case, normally, we're using all of our senses to make a picture of what's going on in the world. What we're going to do in the next couple of modules, is to look at vision and then in the next unit, we'll look at hearing. [MUSIC]