Psychology – Gleitman (0)

Psychology – Gleitman
Blood flow in the brain during different activities: the rate of blood flow is measured by special radiation counters that are placed at various points of the skull and that monitor radiation from mildly radioactive gas injected into the bloodstream. Blood flow pattern depends on what the patient does ( different pattern is found when person is reading aloud, yet another when he watches a moving light and so on).
Ambiguous sights and sounds: The way ambiguous figures are perceived often depends on what we have seen just before . For example, if we are first shown an unambiguous figure of a rat, the ambiguous picture will be seen as a rat. If we are first exposed to an unambiguous face , we see the ambiguous figure as a face. What holds for visual patterns also holds for language . Many utterances are ambiguous. If presented out of context , they can be undestrood in several different ways.
For example, „The mayor ordered the police to stop drinking “.

• May be a command to enforce sobriety among the population at large
  
• May be a call to end drunkenness among the police force
  

How it is understood depends on the context.
Perceptual world of infants: Other psychological accomplishments seem to be part of the innate equipment that all of us bring into the world when we were born. ( EX: infant ’s reaction to heights )
The visual cliff - an infant is placed on the center board of a heavy sheet of glass and his mother calls to him. If he is the deep side of the cliff, he will not crawl across the apparent cliff.This suggests that the perception of depth is not learned through experience , but is built into our system at the very start.
Complex social behaviour in humans: human social interactions are more subtle and flexible than those of animals. For much of human social life is based on the individual ’s rational appraisal of how another person will respond to his own actions : „ If I do this...he will think this...then I will have to do this..“ and so on. Peacockss courtship ritual happens to fail then he has no alternate strategy; all he can do is display his tail feathers again and again.

• Under some circumstances people tend to behave differently in crowds than they do when alone . ( For example panic- when someone shouts FIRE ! in a tightly packed auditorium, the resulting stampede may claim many more vitims than the fire actually itself would have)
  

Dreams as behaviour: Dreams as conscious , mental experiences are essentially private, they go on „inside“ the individual. Two kinds of sleep : quiet sleep and active sleep.

• Quiet sleep: both breathing and heart rate are slow and regular while the eyes are motionless.
  
• Active sleep: pattern different- breathing and heart rate accelerate and most characteristic of all- eyes move back and forth behind closed eyelids in quick irregular darts. ( total of 90 minutes devoted to REM during sleep )
  
• Hypothesis: the direction of the eye movements observed during a given REM periods is appropriate to what the subject recalls having seen while dreaming. When predominant direction of eye movements was up and down, one subject dreamed he had thrown basketballs, looking up the net and shooting, then looking down to pick another ball off the floor .
  
• In contrast , another REM period in which the eye movements were mostly from side to side, produced a dream in which the subject watched two people throwing tomatoes at each other.
  

Dreams as Cognition:
Dreams reflect what we know , what we have experienced , remembered , thought about- activities psychologists call ’cognition’.
Components of the dream were surely drawn from dreamer’s own knowledge , which contains info about flying or tea or car crash etc. Some psychologists have founded: people who remember more of their dreams are more likely to have better and sharper visual mental images in their waking life; perhaps their dreams are more memorable becaus they are experienced in a more vivid pictorial form.
Another factor : the extent to which the dream experience is interfered with by what happens immediately after the sleeper awakes.
Dreams and Social Behavior :
More than 95 percent of our dreams are peopled with others and most revolve around our relations with them .
Culture- culture affects not only what dream is about but also how the dreamer thinks about it when she recalls it later on. In some societies including our own, dreams are generally dismissed as nonsensical fancies, irrelevant to real life.
Dreams and internal conflict- according to Freud , dreams are product of an elaborate clash between two contending forces-unconscious primitive urges of our biological heritage and the civilizing constaints imposed by society. The disguise explains why dreams are so often odd and senseless. Senselessness is only on the surface, a cunning mask that lets us indulge in the unacceptable wish without realizing that iti is unacceptable. ’ some distortions involve various transformations of the unacceptable themes , one is symbolism’. ( riding a horse and walking up a staircase refer to intercourse and passion ).
Dreams and Human Development :
How children learn there is a difference between two realms of phenomena, those which we call subjective and those we call objective . ( How we attain our adult notion of objective reality, how we come to know that the tree in the garden unlikea dream will still be there after we blink our eyes)
Young children tend to think of them as physical objects.
Dreams and Individual Differences:
Dreams are reflection of a fact that people are different.
Comparison between the dreams of normal people and of patients with schizophrenia. Schizophrenics reported dreams that were higly bizarre and morbid. Dreamer is eaten alive by an alligator, nuclear wars and world cataclysms. Themes of bodily mutilation were common, ( woman killed her husband and then stuffed parts of his body into a camel’s head)
In contrast, normal’s dreams were comparatively mild and ordinary. Result fits. Schizophrenics ofthe jump from one idea to another without maintaining firm line of thought. As a result their behavior often appears bizarre. It seems their extremely bizarre and morbid dreams are simply an exaggeration of a condition already present intheir waking life.
Task of Psychology:
What holds for dreams holds for most other psychological phenomena- they can all be viewed from several perspectives. Each perspective is valid but none is complete without the others, for psychology is a field of many faces and to see it fully, we must see them all.
Wilhelm Wundt ( Germany ) and William James (USA)- founders.
General Principles and Unique Individuals:
Psychology’s main purpose is not to describe the distinctive characteristics of a particular individual. Its main goal is to get at the facts that are general for all of mankind. Psychology hopes to find a route back to understand the individual event. It tries to find explanations to some behaviors and once such explanations are found, they may lead to practical applications; to hel counsel and guide , and perhaps to effect desirable changes .
BIOLOGICAL BASES OF BEHAVIOR
Any question about bodily movement must inevitably call for some reference to the nervous system, for tu us it is quite clear that the nrevous system is the apparatus which most directly determines and organizes an organisms reactions to the world in which it lives .
Rene Descartes and the Reflex Concept:
All action was essentially a response to some event in the outside world. Something from the outside excites one of the senses. This transmits the excitation upward to the brain, which then relays the excitation downward to a muscle . The excitation from the senses thus eventually leads to a contradiction of a muscle and thereby to a reaction to the external event which started the whole sequence. In effect, the energy from the outside is reflected back by the nervous system to the animal ’s muscles- the term ’reflex’ finds its origin in this conception.
Basic Nervous Functions : Reception , Integration, Reaction:
Psychologists today agree with Descartes that much of behavior can be understood as reactions to outside events : the environment poses a question and the organism answers it. This approach must lead to a tripartite classification on nervous functions: reception through the senses, reaction from the muscles and glands, and a conduction and integration system that mediates between these two functions.
Stimulus excites receptors, specialized structures capable of translating some physical energy into a nervous impulse. Once a receptor is stimulated, the excitation is conducted farther into the nervous system. Bundles of nerve fibers that conduct excitation toward the brain or spinal cord are called afferent nerves. These fibers transmit their message still farther; in the simplest case, to other fibers that go directly to the effectors, the muscles and glands that are the organs of action. Nerve fibers that lead to the effectors are called efferent nerves.
The transmission path from receptors to effectors is usually more circuitous than this. The afferent fibers often bring their messages to intermediate nerve cells, or inetneurons, in the brain or spinal cord. These interneurons may transmit the message to the efferent nerve cells or send it on to yet other inetneurons. Typically many thousands of such inetneurons have been ’consulted’ before the command to action is finally issued and sent down the path of the efferent nerve fibers.
Nerve Cell and Nerve Impulse:
The neuron is the simplest element of nervous action. It is a single cell, with three subdivisions: the dendrites, the cell body, and the axon . Dendrites are usually branched. The axon may extend for a very long distance , and its end may fork out into several end branches. Impulses from other cells are received by the dendrites; the axon transmits the impulse to yet other neurons or to effector organs such as muscles and glands. Thus the dendrites are the receptive units of the neuron, while the axon endings may be regarded as its effector apparatus. Total number of neurons in the human nervous system has been estimated to be over a 100 billion . There is no way of getting more; once lost , a neuron can never be replaced.
The gap between the axon terminals of one neuron and the dendrites and cell body of another is called the synapse; this is the gap the nerve impulse must cross for one neuron to stimulate the next. Such junctions often involve many more than two cells, especially in the brain.
Types of Neurons:
Some neurons are attached to specialized receptor cells that can respond to various external energies, suhc as pressure, chemical changes, light and so on. These receptor cells can translate or transduce such physical stimuli into electrical changes, which will then trigger a nervous impulse in other neurons. Receptor cells are like money changers, exchanging the various energies impinging from the other world into the only currency acceptable within the nervous system- the nervous impulse.

• Sensory neurons: neurons that convey impulses from receptors toward the rest of the nervous system . In many cases , transmission and transduction are separate functions that are entrusted to different cells. In vision and hearing, there are receptor cells which transduce optic stimulation and air pressures into electrical changes in the cell. These changes in the receptors trigger impulses in sensory neurons that transmit their info to other neurons in the nervous sys.
  
• Motoneurons: have axons that terminate in effector cells. They acticate the skeletal musculature, the muscles which control the skeleton , such as those of the arms and legs . Cell bodies of the motoneurons are in the spinal cord or brain, and their long axons have terminal branches whose final tips contact individual muscle cells. When a motoneuron fires , a chemical event is produced at its axon tips which causes the muscle fibers to contract.
  
• Interneurons: vast majority . They have a functional position that is between sensory and motoneurons. They come in many shapes and forms . They usually show considerable branching, which produces enormous number of synaptic contacts.
  

What happens when a neuron is aroused from rest? The surface of the fiber is stimulated by means of a third microelectrode which applies a brief electrical pulse. This pulse reduces the potential across the membrane for a brief instant. If the pulse is weak , nothing further will happen; there is no impulse. If the strength of the pulse is slowly increased, the resting potential drops still more, but there’s no impulse. This continues until the pulse is strong enough to decrease the potential to a critical point, the threshold.
Now a new phenomena occurs. The potential suddenly collapses; in fact, it overshoot the zero mark and for a brief moment the axon interior becomes positive relative to the outside. This brief flare lasts about 1 millisecond and quickly subsides. The potential then returns to the resting state. This entire sequence of electrical evets is called the action potential.
The all-or-none law:
One point must be stressed. Size of the reaction is unaffected by the intensity of the stimulus, once the stimulus is a t threshold level or above . Increasing the stimulus value above this level will not increase the intensity of the action potential or affect its speed of conduction to other points in the fiber. This phenomenon is sometimes referred to as the allornone-law of neuron stimulation. The all-or-none law clearly implies that the stimulus does not provide the energy for the nervous impulse. It serves as a trigger and no more. Given that the trigger is pulled hard enough , pulling yet harder has no effec . Like a gun, a neuron either fires or does not fire. it knows no in-between.
The number of neurons stimulated: in many cases what happens is that more intense stimulus excites a greater number of neurons. This is precisely what we should expect, for we know that different neurons vary enormously in their thresholds. Thus, a strong stimulus will stimulate more neurons than a weak stimulus. The weak stimulus will stimulate all neurons whose thresholds are below a given level; the strong stimulus will stimulate all of those, plus others whose threshold is higher .
Frequency of impulse: while remaining strictly obedient to the all-or-none law, the individual neuron is nevertheless affected by stimulus intensity. This becomes apparent when we apply a continuous stimulus for somewhat longer intervals. Now we obtain not one impulse but a whole volley. We notice that the size of the action potentials remains the saime whatever the stimulus intensity. What changes instead is the impulse frequency. The stronger the stimulus, the more often the axon will fire. this effect holds until we reach a maximum rate of firing , after which further increases in intensity have no effect. Different neurons have different maximum rates; the highest in man is of the order of 1,000 impulses per second.
Interaction between nerve cells:

• Study of reflex : Movements are controlled by spinal cord
  
• Pierre Cabanis ( wondered whether consciousnrss survives beheading. He concluded it does not and that the body’s twitches after execution are mere reflex actions, automatisms without consciousness. – DURING FRENCH REVOLUTION )
  
• Reflex arc- the reflex pathway that leads from stimulus to response
  

Inferring the Synapse:

• Simple reflex (Sherrington’s study) – reflex considered in splendid neurological isolation, unaffected by activities elsewhere in the nervous system. (doesn’t exist for even the lowliest spinal reflex is modified by higher centers in the spinal cord or the brain). An itch will initiate a scratch reflex but if you’re the catchman in the trampeze act you’ll inhibit it. To remove the effect of higher centers, Sherrington used the spinal animal, usually a dog, whose spinal cord had been completely severed in the neck region. This cut all the connections between the body and the brain, so that spinal reflexes could be studied pure .
  
• Excitation- method simple. Applied mild electric shocks to some point on the spinal animals (spinal dog) skin and observed whether this stimulus evoked a particular reflex response. Results - there had to be conduction across at least 2 neurons – a sensory neuron from skin receptor and motoneuron that acticates muscle fibers.
  
• Spatial summation- several neurons may funnel in upon one output. Stimuli applied to dirfferent points in the saddle area will not evoke a reflex if presented seperately, byt they will if presented simultaneously. The excitatory effects from different regions are all funneled into the same common path.
  
• Temporal summation- a subthreshold stimulus will not elicit the reflex but 2 or more will if presented successivley at intervals of up to half a second
  

Inhibition- neuron can receive both excitatory and inhibitory messages. Two processes summate algebralically; they pull in opposite directions and thus have opposite signs/positive-negative/
The Synaptic Mechanism:

• Presynaptic neuron – sends the neural message
  
• Postsynaptic neuron – the one message is directed to
  
• Within these swellings tiny vesicles including chemical substances called neurotransmitters