Melanie, Corey, Stephanie, Marla, Ashley & Dyneisha VISION Melanie, Corey, Stephanie, Marla, Ashley & Dyneisha

Accommodation: when the lens changes its curvature Pupil: adjustable opening in the center of the eye through which light enters. Iris: a ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening. Lens: the transparent structure behind the pupil that changes shape to help focus images on the retina. Retina: the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin to processing of visual information Fovea: the central focal point in the retina, around which the eye’s cones cluster Blind Spot: the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there Optic Nerve: the nerve that carries neural impulses from the eye to the brain Accommodation: when the lens changes its curvature

-Sensation is a process whereby we transform physical energy from our environment and encode it as neural signals -Vision’s physical stimulus is electromagnetic energy (light waves) which are measured in nanometres

-Electromagnetic spectrum is organized from highest to lowest frequency waves -Only the narrow band between 400 nm and 700 nm are visible to the human eye -Humans have limited vision due to the fact that our vision has evolved in the sun’s light

Relationship Between Wavelength and Pitch -Frequency of a wavelength determines the hue of light and the pitch of a sound: -short wavelength=high frequency, high-pitched sounds (blue colours) -long wavelength=low frequency, low-pitched sounds (red colours)

Relationship Between Wave Amplitude and Sound -Wave amplitude determines the intensity of colours and sounds -Great amplitude=bright colours, loud sounds -Small amplitude=dull colours, soft sounds

What can the human eye perceive? Transduction: the process by which our sensory systems encode stimulus energy as neural messages Eyes receive light energy and transform the energy into neural messages. These messages are processed through the brain into what you see. What are our eyes see are not actually colour, they are pulses of electromagnetic energy that our eyes perceive as colour.

Light Energy The spectrum of electromagnetic energy ranges from gamma rays to radio waves. These two types of wave vary significantly in size, from gamma rays being a diameter of an atom, to radio waves being miles long. When it comes to humans, we can see from the shorter waves of the blue-violet light to the longer waves of red light. Other organisms will have different spectrums that their visual system is able to process. Figure 5.4 The spectrum of electromagnetic energy Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

The wavelength also determines the hue of the colour. Wavelength: The distance from the peak of one light or sound wave to the peak of the next. The wavelength is one important physical characteristic of light which determines our sensory experience of them. The wavelength also determines the hue of the colour. Intensity: The amount of energy in a light wave. This determines the brightness of a colour. Determined by a waves amplitude or height. Figure 5.6 The physical properties of waves Myers: Psychology, Eighth Edition Copyright © 2007 by Worth Publishers

Colour Constancy Colour Constancy: perceiving familiar objects as having a consistency colour. This means even when light changes, the wavelengths reflected by the object remains the same. This demonstrates the way the brain perceives objects, even when the light changes, the object of the colour reflected by the light still looks the same.

Parallel Processing Processing different aspects of a problem simultaneously. Natural completed by the brain for many tasks, including vision. When you view a scene your brain divides it into categories of colour, movement, depth and form. These categories work together to form what you see.

Parallel Processing These subdivisions compare what they see with your memories. Helps you identify what you are seeing. Recognition of objects, faces etc.

Nearsightedness A condition in which nearby objects can be seen much clearer than distant objects. Caused by light rays that enter the eye lens converging before the retina. The rays spread before reaching the retina, causing blurriness.

Farsightedness Condition where objects far away remain clear while close up images are blurred. In farsightedness, light rays from nearby objects converge behind the retina, which blurs them. When the rays reach the retina they are not yet focused.

Rods & Cones Rods and cones are retinal receptors located in the retina of the eye. Both are responsible for detecting light. Rod Cone

Rods vs. Cones Rods Located on the side of the retina. Responsible for detecting objects in poor light (night vision). High sensitivity to dim light, low sensitivity to color. Slower response. Cones Located in the center of the retina in the fovea. Responsible for detecting objects in well lit conditions (day vision). High sensitivity to color, low sensitivity to dim light. Faster response.

Young-Helmholtz Trichromatic Theory Proposed by Thomas Young and Hermann von Helmholtz Also known as the three “color theory” Theory stated that: the retina contains 3 different color receptors (red, blue, green) which overlap each other. when these receptors are stimulated, they will produce any color.

Opponent-Process Theory Proposed by Ewald Hering Theory stated that: visual information is seen in opponent pairs (red-green, blue-yellow, black-white). we never see certain pairs of colors together (reddish-green; greenish-yellow)

What Do Feature Detectors Respond to? Feature Detector = specialized nerve cells found in the brain that respond to a scene's specific features features such as edges, lines, angles and movements different areas of the cortex's respond to different stimulus high level neural cells can respond to specific visual scenes such as familiar faces "vast visual encyclopedia"

Retina’s Reaction to light Light rays from an image is presented to the out surface of the retina where it then focuses the curvature of the lens of the eye than accurately adjusts its thickness to accommodate the object the image, whether it is far or near is then brought into focus the light rays from the image then travel towards the inside of the eye in vertical straight lines this light energy ignites cells within the eye that activate neural signals and form the optic nerve allowing the brain to receive the impulses being sensed by the eye Thus, the lines from the top of presented image hit the opposite end of the retina (the bottom), and the rays from the left side of the retina do accordingly The original image presented to the retina is then upside-down and completely reversed allowing the human eye to see the image correctly Retina: the multilayered surface of the eye responsible for processing light and interpreting visual information through an abundance of different cells that send neural signals to the brain.

People with normal color vision can perceive numbers formed by patterns of colored dots in every circle. If you do not see some of the numbers, you should have your eyes checked and consider working in a job where color discrimination is not critical.