Chapter 3: Sensation and Perception

According to Nolan and Hocken Burry, 2019 Sensation is the process of detecting a physical stimulus, like light, sound, odors, and images

Perception process of taking in the stimuli, interpreting the stimuli and organizing the information received from the stimuli.

Sensation is the result of the sensory receptors.

• Without sensory receptors, no sensation

  • The receptors are specific cells that are attached to the senses and responds to sensory stimulation whether internal or external

In order for the sensory receptors to begin to respond a strong activation will have to occur, the threshold.

• Two kinds of  thresholds

  • Absolute threshold: smallest possible level sensory stimuli can detect, 50% of the time.

  • Difference threshold: Noticeable difference, the minimum threshold that a person can detect, 50% of the time.

    • According to Weber’s law, more intense the stimulus, the greatest increase in the stimulus intensity required for the increase to produce a just noticeable difference

  • Transduction occurs when a stimulus is converted into an electrical signal in the nervous system.

    • Your ears receive energy/soundwaves, and transduced the soundwaves into neural messages so the broom and then processed as sounds the brain.

Sensory Adaptation:Gradual decline in sensitivity to a constant stimulus

• Allows your attention to be free to detect new information rather than what is constant.

  • Senses adaption, like when we become nose blind to our cologne,or get used to cold water, or sour foods.

Light is a stimulus for vision, which travels in waves.

• Vision is least developed at birth

  • Newborn can see 20-30 feet, whale normal humans can see 200-400, by six months infant visual is close to a normal adult

• First light waves reflect from the object to your eyes through a clear membrane (cornea) that covers the front of the yem which helps gather and direct the light

• Pupil of the eye is a black circle in the center of the iris

  • Pupil of the eye is a portal which regulates the flow of light to the retina

    • Allows person to see images

  • Lens is behind the pupil:

    • Transparent structure that allows eye to focus at varying distances

  • Accommodation refers to the lens ability to focus on near and far objects.

  • Retina is a thin layer of tissue that lines the back of the eye on the inside

    • Converts  light that enters the eye into electrical signals your optic nerve sends to your brain to create an image

    • Processes information gather by the photoreceptor cells and send them information to the brain via optic nerve

    • Two photoreceptors, rods and cones.

      • Rod: for night vision, and have light sensitivity, 

        • Work at much lower level of light

        • Rods do not help with color vision which is why what we see at night is in a grayscale

      • Cones: require more light and used to see color

        • Three types of cones, blue green and red

        • Human eye has 6 million cones

        • Math of the cones are focused in the fovea, small bit in the back of the eye that helps with sharpness or detailed images

      • Optic disk is one part of the retina, lacks rods and codes

        • The lack of rods and cones create a blindspot in vision

      • Before visual information is sent to the brain, specialized cells called the ganglion cells process the information

        • Located in the retina

        • collect information about the visual world from bipolar cells and retinal interneurons

          • Information is in the form of chemical messages sensed by receptors on the ganglion cell membrane