Chapter Six- Sensation and Perception

In this chapter I learned about thresholds, color vision, and how we form perceptions. I will admit that I did not find this chapter as interesting compared to some of our previous chapters.

Absolute thresholds are the minimum stimulation needed to defect a particular stimulus 50 percent of the time. These thresholds are illustrated through faint stimuli seeing things from a distance such as a light tower or feeling a bug land on us. Absolute thresholds help us to detect particular sounds, pressures, lights, taste and odors. Our absolute thresholds vary with age. This means that as we age we might be less sensitive to a smell or sound than we were at a younger age.

Color vision is what helps us to define a red tomato or green grass. However, these objects really are not those colors. What I am referring to is that all objects have pigments and it is through reflected light that we are able to see those pigments. So for a tomato the light reflects the color red and for most grass the light reflects the color green. Colors can be created through combining waves of light which consist of three primary colors: red, blue, and green. This is where the Young-Helmholtz trichromatic theory comes in, which implies that the cones in our eyes work in groups of three. The retina has three color receptors which is sensitive to a color. This theory makes sense because the retina receptors are red, green, and blue. This means that we are more sensitive to red, green, and blue things. Color deficient people lack red and green cones(which when combined are sensitive to yellow) have problems seeing certain reflected colors. One out of fifty people are "color blind"(color blind is the incorrect terminology for this situation) or color deficient. (These people are usually male and this trait is usually genetically linked through gender.)

Form perception is another thing I learned in this chapter. This section talked about figure-ground and grouping principles. Figure ground is the organization of the visual fields into objects that stand out from their surroundings. Examples of this would include; face detection, recognizing voices, and or other objects. Grouping is the perceptual tendency to organize stimuli into coherent groups. This allows us to organize our figure-ground data and put it into groups. The principles that follow this idea are: Proximity, Similarity, Continuity, Connectedness, and Closure. Proximity refers to figures being together or near one another. Similarity is where we take similar or like objects and group them together. Continuity is where we perceive smooth, continuous patterns. Connectedness is where items are grouped together because they are uniform and linked. Closure is where we piece everything together and create a whole object. (See figures on page 265 in our text book for specific examples.)