Psychology 10:  Introduction to Psychology

Professor Halford Fairchild

Lecture Notes for February 3, 2009

 

Sensation and Perception:  Definitions

 

1.    Sensation:  The process of receiving inputs.  Recall that the human bio-physical system is one Inputs à Processing à and Outputs.  Sensation is about how inputs get inputted.

 

2.    Perception:  The process of processing.  Making sense out of sensations.  Using past experiences and memory to interpret external events.

What comes first? Sensation or perception?

 

3.    Senses:  vision, audition (hearing), touch (including temperature and pain), gestation (taste), olfaction (smell), kinesthesia (body orientation in space), pain (across sense modalities), and those in combination.

 

4.    Expectations and Perceptual Sets:  We see what we expect to see.  For example, read the following words:  MACARTHUR, MACDONALDS, MACHINE.  Magicians perform magic by manipulating expectations (creating perceptual sets) and

 

5.    Steps in Sensation:  Accessory structures (eyes, ears, skin, nose, mouth and tongue) focus and modify incoming stimuli.  These structures’ receptor cells then transduce (change) the physical energy into neural energy, and are particularly responsive to changes in physical energy (constant stimulation produces adaptation, or a decreasing responsiveness). 

 

6.    Absolute thresholds:  the minimum amount of stimulus that can be detected (50% of the time).  (see question 3, today's quiz)

 

7.    Difference thresholds:  the minimum amount of change in stimulus that can be detected.  (Weber’s law – the smallest detectable difference in stimulus energy is a constant fraction of the intensity of the stimulus:  if you can barely detect the difference between 10 ounces and 11 ounces, then you would barely be able to detect the difference between 100 ounces and 110 ounces).

 

8.    Sensory energy:  For light and sound, the energy is in the form of waves, where the key terms are wavelength frequency (hue or tone), and amplitude (intensity).

 

Vision

 

1.    The eye is the accessory structure for vision (see p. 85).  It is very much like a camera, where we have a retina instead of film.  And instead of taking the film to a one hour photo processor, the retina sends its information to the brain for processing.  Some processing, however, takes place at the level of the retina (sharpening of the image, color processing).

2.    The retina is comprised of many types of cells.  Photo receptors may be rods or cones.  Rods are for low light sensitivity, and do not detect color; cones are for color processing and detailed vision, and are concentrated at the point where incoming light gets focused (the fovea). 

 

The process of dark adaptation takes place due to chemical changes in the rods, and accounts for sensitivity differences on the order of 10⁴ (10,000). 

 

Bipolar cells and ganglion cells (and horizontal cells) process information from the rods and cones prior to sending the information to the brain, for additional processing. 

 

Note that the image at the level of the retina is blurred, but it gets sharpened on the way to the brain, and in the brain itself.

 

3.    Color vision.  Different wavelengths of light convey different colors.  Hue is the color, saturation is the purity of the color.  Brightness refers to the overall intensity of the light.  Two theories account for color vision, and both are necessary:  the trichromatic theory of color vision (due to three types of cones – like an RGB color monitor), and opponent process (which accounts for afterimages).

 

Audition (Hearing)

 

1.    Sound is produced by pressure changes in air molecules (other substances also carry sound, including water and various solids). 

 

2.    The ear is the accessory structure for sound, and includes the pinna (the outer ear, for gathering sound), the ear drum or tympanic membrane), the middle ear (consisting of three small bones – the hammer, the anvil and the stirrup, which amplify the vibrations), and the inner ear or cochlea, which transduces (changes) the physical vibrations into neural energy.  Within the cochlea, which is curled like a snail, is the Basilar membrane and hair cells. 

3.    The auditory cortex processes sounds, where certain cells also respond to other stimuli (such as visual stimuli), thus raising the notion of multi-sensory cells.  According to the text, the auditory cortex is larger in trained musicians.

 

4.    An auditory miracle:  How is it that we can recognize people’s voices – where everyone’s voice is unique like a fingerprint?

 

Taste and Smell

 

1.    Smell and taste are components of a flavor system.  The olfactory system detects odors, the taste system detects chemicals.  Odors are more important.  Note that variations in our nutritional state can affect taste and flavor (e.g., things taste better when you’re really hungry),and warm foods may taste sweeter. 

 

2.    See p. 97 for a figure of the olfactory system (or the flavor system).  Note the connection between odors and emotions.

The olfactory bulb is the part of the brain that processes smell.

 3.    Taste buds are called papillae (pronounced “puh-PILL-ee”).

 

Touch

 

1.    The skin is the largest organ of the body, has nearly two square yards of surface area, and weighs more than 20 pounds.  It has hair nearly everywhere.

 

2.    The skin can detect touch, the location of the touch sensations, and warm and cold.

 

3.    Pain is sensed in the skin (but the other organs – ears and eyes and tongue and muscles and joints– can also sense pain) and has many emotional aspects. 

 

4.    Pain is moderated by natural analgesics, such as endorphins, and by processing at the level of the spinal cord, according to gate control theory.

 

5.    Acupuncture is shown to have benefits, but more research is needed.  Acupuncture shows that much is known about the body that does not fit into Western scientific models, and this knowledge is deep, and old.

 

6.    Kinesthesia refers to sensing body position.  The inner ear’s semicircular canals help determine balance, but the eyes are also involved here.  (Stand on a Bosu ball and close your eyes.)

Perception

 

1.    Gestalt principles of perceptual organization:  figure-ground, grouping (proximity, similarity, continuity, closure, texture, simplicity, common fate, synchrony, common region, connectedness).  See pp. 106-107.

 

2.    Depth Perception:  Many cues provide information about depth.  Some of these are physical cues, such as the feedback we get from the muscles in our eyes, or due to the different images we get from having two eyes (binocular cues).  Some are due to the stimuli themselves – relative size, height in visual field, interposition, linear perspective, light and shadow, textural gradient).  See the figure 3.21 on p. 108.

Quiz Items:

When you perceive an object as being closer to you because it blocks out part of the background, you are using the depth cue called Interposition

 

3.    Perceptual Constancies.  Although retinal images may change, we don’t think that the physical world has changed – thus a book that is closer to us has a larger retinal image, but we don’t see it as changing size (size constancy).  Objects retain their perceived shape although they may be rotated in space (shape constancy).  And objects maintain their perceived brightness even though they may emit or reflect different light intensities as they go from light to shadow (brightness constancy).  See pp. 111-112.

 

4.    Optical Illusions are informative of how perception works. See p. 112.

 

5.    Bottom-up Processing:  putting together our perceptions based on their raw, sensory elements.

 

6.    Top-down processing:  perceiving the world according to our memory, expectations, and cognitive (thinking) processes. 

 

Perceptual Development

 

1.    Although many abilities exist at birth, they also develop (improve) over time (through maturation and experience).  See the visual cliff experiment on pp. 117-118 and our reader.

 

 

Attention

 

1.    Attention refers to the process of directing and focusing on certain stimuli (which may be external or internal).  It takes mental energy, and is limited.  It is difficult to read and talk at the same time. 

 

2.    Reading our textbook takes attention, which is why I recommend:  (1) spread it out over a few days; and (2) highlight key points.

 

3.    When you attend to something, you may miss something else happening in your environment.  This is called inattentional blindness. 

 

4.    Attending to more than one thing at a time can be reflected in brain activity.