Goldstein Chapter 1
Some questions we will consider
Why Read This Book?
The Perceptual Process
The Stimulus
Environmental Stimuli and Attended Stimuli
The Stimulus and Recptors
Electricity
Transduction
Transmission
Processing
Experience and Action
Perception
Recognition
Action
Knowledge
How to Approach the Study of Perception
Measuring Perception
Description
Recognition
Detection
The Absolute Threshold
The Difference Threshold
Magnitude Estimation
Search
Other Methods of Measurement
Something to Consider: Threshold Measurement Can Be Influenced by How a Person Chooses to Respond
Lecture 1
Definition
PSY 3120 is the study of our relatively automatic responses to the physical events and energies of our environment.
Responses to be studied will vary from the rudimentary to the complex
Sensation: Simple responses to external stimulation
Perception: Complex responses to external stimulation
Responses are automatic, mostly NOT under cognitive control.
Perception Is a Biological Process
Assumptions
1) Perceptual experiences are associated with/correspond to/represented by characteristic patterns of neural activity in the brain. The philosophy underlying this assumption is called materialism.
2) Neural activity does not resemble the objects we perceive. This means that perception is a symbolic process. The neural activity is a symbol of the object perceived, not a replica of it.
3) All behavior is in principle explainable, predictable, and controllable.
Distinguish “In principle” from “In practice”
In principle,
The behavior of a falling leaf is in principle explainable, predictable, and controllable.
But in practice,
the task of actually measuring all the variables that we would have to measure – air pressure, shape of the leaf, air movements, temperature – would be daunting, so daunting that we might never actually do it in practice.
4) Finally, the explanations are in terms of brain processes. (This is a restatement of 1 above.)
This means that scientists studying S&P believe that all experience corresponds to neural activity in the brain. So, to understand perception we must understand the brain. We seek neural mechanisms underlying perceptual phenomena.
Basic Model underlying much of the research – from G8, p. 6
Note that there is no “beginning” in the figure, emphasizing that perception is part of a continuous process.
Studying Ourselves – Is psychology different in principle from physics or chemistry?
We can treat the human organism as any other object of study.
Some of the behaviors are easily observed – Verbal behavior is the best example.
Some are as yet unobservable and must be inferred – the activity of neurons in the temporal lobe of the brain when an object is viewed.
This is no different in principle than the study of the rocks of physics or the study of compounds in chemistry.
Some of the behaviors of objects are easily observed.
Some, the behaviors of molecules and atoms, are less easily observed or not yet observed and must be inferred.
Why Study Sensation and Perception?
What does S&P have to do with psychology?
1. Sensations and Perceptions are behaviors, so they’re qualified to be part of the study of psychology, even though they’re so automatic that we hardly ever think of them and we may not be interested in them.
Just as some people climb mountains because they’re there and not yet climbed, some psychologists study S&P because it’s there and not yet understood.
2. It’s important to understand and perhaps control certain perceptual phenomena
a. Color blindness - understanding and possible correction
b. Tone deafness – why some people can’t carry a tune
c. Effects of early deprivation or unusual experience on development of sensory capabilities.
d. Hallucinations – effects of certain drugs, such as LSD; phantom limb pain
e. Creation of perception in those for whom it doesn’t exist
Vision for the blind
Hearing for the deaf
Movement and sensation for persons without limbs: http://www.cbsnews.com/video/watch/?id=50137987n
f. Machine perception
OCR: Being able to recognize text and convert it to a Word document.
Being able to recognize speech and covert it to written text
Teaching Mars rovers to identify and thus avoid rocks, cliffs, crevices
Being able to recognize a spoken name and dial that person’s phone number.
Recognizing when a heart is beating correctly. Recognizing fibrillation.
Being able to recognize a smile – From Consumer Reports
3. S&P mechanisms may be similar to the mechanisms underlying other more complex or elusive phenomena.
Learning about these processes in the study of S&P may help us understand these other phenomena.
For example, the processing of wavelength of light leads to a categorization of wavelengths into 6 rough categories – red, orange, yellow, green blue, and violet. Understanding this categorization process may help us understand other categorizations that we make, such as . . .
The processes underlying the liking/disliking of people – categorization analogous to the categorization that is color perception.
The processes underlying the experience of humor. Some things are funny. Others are not.
The processes underlying the experience of beauty.
Example Questions that persons studying S&P attempt to answer
1. What external/internal stimulation do we perceive? – light, sound, touch, hot/cold, chemicals
Do we not perceive? – magnetism, ultraviolet radiation, infrared radiation
2. What are the explanations of perceptual deficits or extraordinary abilities?
Color perception deficiency, tone deafness, inability to perceive motion, feel pain, perfect pitch; extraordinary experience of colors, synesthesia.
3. To what extent are our perceptual capabilities innate, such that they would exist without any prior exposure to stimuli.
For example, are our responses to a cliff innate? How about our responses to a snake?
4. To what extent do our perceptual capabilities depend on a history of exposure? -
What happens when vision is introduced in an adult who has never seen.
See the movie, At First Sight.
5. Why do we perceive only 6 categories of hue – red, orange, yellow, green, blue, violet?
6. Why are there octaves in pitch? – A pitch twice as high as another seems more similar to the other than a pitch only 1 ½ times as high?
7. How and where are images of our experience stored?
Why is the memory of a smell so much less distinct than the memory of a face?
In a single place? In multiple places in the brain?
8. How can our visual system create the dimension of depth, since our eyes are on a single two-dimensional plane?
9. Why do perceptions remain constant even though the external stimulation which gives rise to them changes drastically? Perceptual constancies
10. Why do persons with autism experience the world so differently from those without autism.
“It is a world filled with anomalies, in which everyday sensations can be overwhelming: A school bell can feel like a dentist’s drill, a scratchy shirt like a swarm of fire ants. In other cases the autistic person may feel so little sensation that she’ll try to fill the vacuum and create some sort of order — hence the rocking, twirling, hand-flapping, noisemaking behaviors that can discomfit and alienate onlookers.” From a review by David Dobbs of The Autistic Brain by Temple Grandin and Richard Panek.Complementary Approaches to the study of Perception
The Psychophysical Approach – G8 p. 11
Psychological approaches involve the use of verbal reports or other overt behavior as the gauge of perception.
Focus on relationship between external stimuli and overt behaviors, including verbal report
Behaviors include:
Verbal reports of experience: Much early research involved showing an object to a research participant who then described the basic “sensations” he or she experienced when looking at the object.
Detection: Detection studies are often used to determine thresholds. How much monosodium glutamate is required for persons eating Chinese food to notice the enhanced flavor. How much cilantro must be present in food before my wife won’t eat it?
Discrimination: Methods to determine just noticeable differences between stimuli or stimulus quantities. How big of a difference in sodium content will be noticed by people who eat soup?
Magnitude estimation: Methods used to assess the quantitative relationship between stimulus amounts and psychological amounts. How much brighter must a light be made to be perceived as twice as bright? How much more intense must a stereo system be to be perceived as twice as loud?
But wait!! If we’re interested in the brain, why are we studying external behaviors?
1) Inferences about brain activity can be drawn from psychophysical approaches
Careful behavioral research has yielded very good inferences concerning physiological processes.
Example: Helmholtz postulated the existence and described the nature of the three types of cones in the late 1800s, more than 100 years before first observations of cones
Ewald Hering postulated the existence of opponent processes in color perception many years before the first evidence of those processes was presented in the 1960s.
Use of dark adaptation curves lead to postulation the existence of two receptor classes.
But the above were easy, relative to what lies ahead.
2) Sometimes the practical results of such experiments, e.g., the difference in sodium content of potato chips that’s just noticeable, is what we need.
The Physiological Approach – G8 p. 11
The physiological approach focuses on relationships between external stimuli and neural structures and activity
Methods, some of which are gruesome
1. Single cell recording
2. Multiple cell recording
a. Evoked potential recording – electrode attached to skin and record activity.
b. Brain scan techniques
Computer Assisted Tomograph CAT scans
Positron Emission tomography (PET scans)
Magnetic Resonance Imaging (MRIs and fMRIs)
Transcranial Magnetic Stimulation: (TMS) Brief, strong pulse of magnetic energy thru the scalp – results in a temporary cessation of function of involved neurons
3. Lesion technique – destruction of parts of the brain and observation of results. The TMS procedure mentioned above does this without permanent damage. Lesions occurring as a result of injury.
4. Staining – injection of drugs which are absorbed by neural activity. The presence of these drugs can be indicated either visually or using special equipment.
5. Brain stimulation – Stimulating parts of the brain and recording the sensations, if any, that result from such stimulation. During surgery for reasons other than the brain stimulation.