Sensation and Perception Flashcards
Pupil
The hole in the iris, which contracts in bright light and expands in dim light, and through which light enters.
Lens
The part of the eye located right behind the iris, and which helps control the curvature of the incoming light and can focus near or distant objects on the retina.
Max Wertheimer
(1880 – 1943) Co-founded Gestalt psychology, beginning with visual illusion known as the phi phenomenon. Concluded that the experience of this visual illusion has a “wholeness” that is different from the sum of its parts. Like other Gestalt psychologists, believed that an analysis of experience into parts is not a valid way of studying our conscious experience.
The Gate Theory of Pain
Created by Ronald Melzack and Patrick Wall. Proposes a special “gating” mechanism that can turn pain signals on or off, thus affecting whether or not pain is perceived. The gating mechanism is located in the spinal chord, and is able to block sensory input from large, thick sensory fibers before the brain is able to receive the pain signals.
Vestibular Sense
Has to do with our sense of balance and of our bodily position relative to gravity. The receptors for balance, the semicircular canals, are in the inner ear, above and behind the cochlea.
Kinesthesis
The sense that provides information through receptors in the muscles, tendons, and joints, enabling humans and other animals to control and coordinate their movements, including walking, talking, facial expressions, gestures, and posture. Also called kinesthesia; kinesthetic sense; movement sense.
Afterimages
Visual sensations that appear after prolonged or intense exposure to a stimulus. Afterimages have been used to support Hering’s theory of color vision, since the color of the afterimage will be the “opposite” of the original color.
2 Types of Processing
(relevant for all senses, not just vision)
- Bottom-up processing (data-driven processing): Responds directly to components of incoming stimulis on the basis of fixed rules and then sums up components to arrive at the whole pattern
- Top-down processing (conceptually driven processing): Guided by conceptual processes such as memories and expectations which allow the brain to recognize whole objects and then the components
4 Visual Constancies
- Size constancy: Tendency for the perceived size of an object to remain constant despite variations in the size of its retinal image
- Shape constancy: Tendency for the perceived shape of an object to remain constant despite variations in the shape of its retinal image
- Brightness constancy: Tendency for the perceived brightness of an object to remain constant despite changes in illumination
- Color constancy: Tendency for the perceived color of an object to remain constant despite changes in the wavelength of the light we see (e.g., colored glasses)
Proximal Stimuli
vs.
Distal Stimuli
The distal stimulus is the actual object or event out there in the world. The proximal stimulus is the information our sensory receptors receive about the object. In the case of vision, the proximal stimulus is the image on the retina.
Frequency Theory of Pitch Perception
The basilar membrane vibrates in synchrony with a sound, causing auditory nerve axons to produce action potentials at the same frequency. The downfall of this theory, in its simplest form, is that the refractory period of a neuron is typically about 1/1000 second, so the maximum firing rate of a neuron is about 1000 Hz, far short of the highest frequencies we hear.
Light Adaptation
When you walk out of a dark movie theater into a bright, sunny day, the visual process that takes place is called light adaptation. Less is known about the physiological basis for this.
Objective Dimensions of Sound
- Frequency: number of cycles per second, measured in Hertz (Hz); one Hz is one cycle per second; frequency is inversely related to wavelength; human sensitivity ranges from 20 Hz to ~ 200,000 Hz, with maximum sensitivity at about 1,000 – 3,000 Hz
- Intensity: amplitude or height of sound wave, measured in bels, or more commonly, decibels (one bel = ten decibels); sounds > 140 decibels tend to be painful to the human ear
Brightness and Illumination
Brightness is related to illumintaion, but it is not the same thing as illumination. Illumination is a physical, objective measurement that is simply the amount of light falling on a surface. Brightness is the subjective impression of the intensity of a light stimulus.
Difference Thresholds
How different two stimuli (in magnitude) must be before they are perceived to be different 50% of the time. Obtained by comparing a “standard stimulus” with a “comparison stimulus.” The comparison stimulus is adjusted until, at some point, the subject thinks that the comparison stimulus is equal to the standard stimulus, even though it isn’t. After repeated trials, the differences between the standard stimulus and the comparison stimulus are averaged. The important thing is not the difference itself, but the ratio of the difference threshold to the “standard stimulus.” This ratio is the basis of Weber’s Law.
4 Broad Categories of Touch
- Pressure
- Pain
- Warmth
- Cold
Cochlear Nerve, also called Auditory Nerve
The cochlear nerve or auditory nerve is a bundle of nerve fibers that carries hearing information from the cochlea of the inner ear directly to the brain.
Physiological Zero
A temperature that is felt by the skin as neither warm nor cold and that under ordinary conditions usually falls at about 85° to 90°F.
Signal Detection Theory
(in the context of psychophysics)
Suggests that other, nonsensory factors influence what the subject says she senses. These nonsensory factors include experiences, motives, and expectations. Response bias refers to the tendency of subjects to respond in a particular way due to nonsensory factors. Unlike the earlier psychophysics, signal detection theory gives us a way to measure both how well the subject can sense the stimulus (sensitivity) and response bias.
Signal Detection Theory
Signal detection theory is a means to measure the ability to differentiate between information-bearing patterns and random patterns that distract from the information.
Fovea
The middle section of the retina, containing only cones. As you move outward, the number of rods increases while the number of cones decreases. Therefore, visual acuity is best here, and this is the part of the eye that is most sensitive in daylight. At the periphery of the retina, there are only rods.
Duplicity (or Duplexity) Theory of Vision
The retina contains two kinds of photoreceptors: cones and rods. Cones produce photopic or color vision, whereas rods produce scotopic or corlorless night vision. Cones also give us the ability to see fine detail (rods do not).
The Steps of Sensory Information Processing
(common to all sensory systems)
- Reception: Each sensory system has receptors that react to physical external energy.
- Transduction: the translation of physical energy into neural impulses or action potentials.
- Once transduction occurs, the electrochemical energy is sent to various projection areas in the brain along various neural pathways and can be processed by the nervous sytem.
Sir Francis Galton
(1822 – 1911) One of the first researchers interested in individual differences. For six years, maintained an anthropometric lab in which he measured the sensory abilities of nearly 10,000 people.
Absolute Threshold
The minimum of stimulus energy needed to activate a sensory system.
Dichotic Listening
Technique used in the lab to study selective attention and lateralization of brain function within the auditory system. The two ears are simultaneously presented with two different messages. Generally, listeners are asked to shadow; that is, to repeat one of the messages as it is presented. Using this method, it has been demonstrated that listeners can indeed attend to one message and dampen out the other one.
Yerkes-Dodson Law
Performance is worst at extremely low or extremely high levels of arousal, and optimal at some intermediate level.
Wolfhang Köhler
(1887 – 1967) Gestalt psychologist who developed the theory of isomorphism.
Psychophysics
The branch of psychology that deals with the relationships between physical stimuli and mental phenomena.
Ames Room
Erroneous depth information confuses our notion of size in certain situations. In an Ames Room, the back left corner of the room is almost twice as far away as the back right corner, and there are distortions of floor-to-ceiling height. However, if you view the room through the peephole provided, the trapezoidal shape of both the back wall and the windows at the rear of the room make the room look like a normal rectangular room, with a back wall apparently perpendicular to the line of sight. Thus, someone standing by the larger left rear window appears equally as far away as someone standing at the closer right rear window, even though the visual angles subtended by the two people are quite different. The person on the left appears much smaller than the equally sized person on the right because you have been fooled into believing that the difference in visual angles is not due to a difference in distance.
The Significance of
Visual Angle
The visual angle determines the size of the image on the retina. The 2 things that determine the visual angle (and thus the retinal size of the object) are the size of the object and the distance between the object and the eye.
Eleanor Gibson and Richard Walk
Developed the visual cliff apparatus, which is used to sudy the development of depth perception.
Wavelengths of light visible to the human eye
~ 400 – 800 nanometers
Simultaneous Brightness Contrast
A target area of a particular luminance appears brighter when surrounded by a darker stimulus than when surrounded by a lighter stimulus. An explanation for this phenomenon is lateral inhibition: if a retinal cell is excited, neighboring cells will be inhibited. Because the surrounding cells are inhibited, they do not fire as often, and the corresponding area appears not as bright. Lateral inhibition sharpens and highlights borders between light and dark areas.
Crossings of Visual Information
The image of the stimulus on the right side of each eye’s visual field forms the left half of each eye’s retina, and vice versa. At the optic chiasm in the brain, fibers from the nasal half of the retina cross paths. The nasal fibers from the left eye go to the right side of the brain, and vice versa. However, the fibers from the temporal halves of the retina do not cross paths. Thus, all the information from the left visual field of both eyes is processed in the right cerebral hemisphere, and vice versa.
Chromatic vs. Achromatic Color
Chromatic colors are any color in which one particular wavelength or hue predominates. For example, blue and green are chromatic colors, while white, gray, and black are achromatic colors, as they have no dominant hue (all wavelengths are present in equal amounts within those colors).
Rods vs. Cones
The two kinds of photoreceptors in the human retina are rods and cones. Cones are used for color vision and for perceiving fine detail. Cones are most effective in bright light, and allow us to see chromatic and achromatic colors. In reduced illumination, rods function better than cones but allow perception only of achromatic colors. Rods have low sensitivity to detail and are not involved in color vision. There are many more rods than cones in the human eye.
Limen
Another word for “threshold.” For instance, “subliminal perception” refers to perception of stimuli below a threshold––in this case, below the threshold of conscious awareness.
