Sensory Processes

1		We experience the world through our senses. However, some people suffering from experience sounds as colors or tastes as touch. The study of the relationships between physical characteristics of stimuli and sensory capabilities is called . One thing that psychophysicists study is the intensity need to detect a stimulus. The minimal intensity needed to detect a stimulus 50% of the time is called the . People are sometimes uncertain about whether they have detected a stimulus and set their own to decide whether they have detected it or not. The theory that is concerned with the factors that influence sensory judgment is called theory. A stimulus so weak or brief that it cannot be perceived consciously is called a stimulus. People must also be able to distinguish between stimuli. The smallest difference between two stimuli that people can perceive 50% of the time is called the threshold or the . states that the jnd is directly proportional to the magnitude of the stimulus with which the comparison is made. Sensory systems are attuned to changes in stimulation. The diminishing sensitivity to an unchanging stimulus is called .

The Sensory Systems

2		results when the focuses an image in front of the while occurs when the lens focuses the image behind the retina. The cells in the eye that detect color are called , while the cells that detect black-and-white and brightness are called . Rods and cones translate light waves into nerve impulses with the action of protein molecules called in the process of . Rods and cones have synaptic connections with , which in turn have synaptic connections with ganglion cells, the axons of which form the . A small area of the retina containing only cones is called the , where the cones have individual connections to bipolar cells. Our ability to see fine detail, or our , is greatest when the visual image projects directly onto the fovea. We must adapt to different levels of illumination. The progressive improvement in brightness sensitivity that occurs over time in conditions of low illumination like in a movie theatre is called . Several theories suggest how we sense color. According to the theory, there are three types of color receptors in the retina, while according to the theory, each type of color receptor is sensitive to two different wavelengths. The theory is a more modern theory, combining both theories. Feature detectors in the receive and integrate various sensory nerve impulses originating in the retina. Visual information is finally analyzed and recombined in the . Psychologists also study how we detect sound. Sound waves are measured both in the number of sounds waves, or cycles, per second, which is the of the sound waves, and in their vertical size, or . Sound waves travel into the auditory canal of the ear and stimulate the three tiny bones of the middle ear, which amplify the sound wave. The pressure created sets the fluid in the into motion. The fluid waves that result vibrate the membrane and set the cells into motion. Neurotransmitters are then released and nerve impulses are sent to the brain. There are two theories of how we code pitch. The theory suggests that nerve impulses sent to the brain match the frequency of the sound wave, while the theory suggests that specific point in the cochlea where the fluid wave peaks and most strongly bends the hair cells serves as a frequency coding cue. A type of hearing loss called deafness occurs when the system sending sound waves to the cochlea is damaged, while deafness occurs when inner ear receptors or the auditory nerve is damaged. is the sense of taste, while refers to our sense of smell. Receptors called concentrated on the tongue allow us to taste things. Some researchers believe that , chemical signals found in natural body scents, may affect human and animal behavior. Humans are sensitive to at least four tactile senses: touch, pain, warmth, and cold. The body senses include , which provides us with feedback about the positions of our muscles and joints and the sense, which is the sense of body orientation or equilibrium.

Perception: The Creation of Experience

3		Perception is an active, creative process. To create perceptions, the brain uses both - processing, which involves taking in individual elements of a stimulus and then combining them into a unified perception, and - processing, which is when the brain uses existing knowledge and expectations to perceive a stimulus. Perceptions have organization and structure. Gestalt theorists discovered many of the basic principles of organization. For example, we tend to organize stimuli into foreground figures and backgrounds, a process called - relations. The four Gestalt principles of organization are , , , and . Perception involves hypothesis testing. Recognizing a new stimulus, for example a flying animal with feathers, wings, and a beak as a bird, requires use of a perceptual . Readiness to perceive certain stimuli in a certain way is called a perceptual . We can recognize familiar stimuli under different environmental conditions because of perceptual .

Perception of Depth, Distance, and Movement

4		To judge depth, the brain relies on both cues, which require one eye, and cues, which require two eyes. Depth cues rely on , in which each eye sees a slightly different image. A second binocular distance cue called is produced by feedback from the muscles that turn our eyes inward to view a near object. - studies indicate that perception is influence by environment, as does work with animals experiencing and people who have hd their vision .