Physiology and Psychophysics Ch.8

Advances help adress what question

By what mechanisms do empirical events come to be represented in consciousness? Or “How does the out there, get in here?”

 scientific method focused on

the study of physiological mechanisms by which we come to know the physical world.

• • Everything from sense perception to motor

  reactions was studied intensely and gave birth

  to experimental psychology

reaction time

The period of time between presentation and response to a stimulus. (Nevil Maskelyne and his assistance David Kinnebrook)

 Friedrich Basel (1784-1846), German astronomer, studied reaction time and found

that the discrepancies were not due to incompetence, but to Individual Differences

Early reaction-time study illustrated importance of

individual differences and demonstrated the importance of discrepancy between objective and subjective reality.

• Evident that there was not a point-to-point correspondence between physical reality and the psychological experience of that reality.

descarete view on nerves

 A nerve consisted of fibers that connected sense receptors to the brain. These fibers were housed in hollow tubes that in turn transmitted the “animal spirits” from the brain to the muscles.

hartleys view on nerves

Nerves were the means by which “vibrations” were conducted from the sense receptors to the brain and from the brain to the muscles

What did bell do

 British physiologist, who researched the anatomical and functional

discreteness of sensory and motor nerves.

what did bell discover

• that sensory nerves enter the posterior (dorsal) roots of the spinal cord

• motor nerves emerge from the anterior (ventral) roots.

nerve physiology was then separated into

study of sensory (sensation) and motor (movement)

functions.

magendie

 French physiologist, found similar results 11 years later

without knowing about Bell or his work.

magendie findings

• No more nerve conveyors of vibrations or spirits

• Sensory nerves carried impulses forward from the sense receptors to the brain.

• Motor nerves carried impulses forward from the brain to the muscles and glands

• “a law of forward direction

muller findings

 Demonstrated that each of the five types of sensory nerves results in a characteristic sensation.

• In other words, each nerve responds in its own way regardless of the stimulation which activated it.

what did muller say about the sensory system

maximally sensitive to a specific type of stimulation but may be stimulated by other forms of energy.

adequate stimulation

The central nervous system, not the physical stimulus, determines our sensations

helmholtz disagreed with the concept of

vitalism

vitalism states

life comes from a force beyond physical and chemical processes alone…life is more than such a reductionist view…Müller supported Vitalism

• because not physical “life force” not conductive to scientific analysis

materialist position stated (helmholtz and others)

that life could be explained in terms of physical and chemical processes and thus, there is no need to exclude the study of life or anything else from the realm of science

through research h was able to

demonstrate the application of the principle of conservation of energy to living organisms.

• Measured the speed of nerve conduction, finding nerve conduction in humans to be between 165 and 330 feet per second.

• This provided further evidence that physical–chemical processes are involved in our interactions with the environment rather than some mysterious process

sensations are faw elements of

experience

perceptions are

sensations after given meaning by the persons past experience

 To explain the transformation from sensation to perception dependent 

he relied on the ideas of unconscious inference of past experience.

helmholtz devision of color theory

 Devised a theory of color vision which proposed three types of color receptors corresponding to the three primary additive colors

firing the receptors in various combinations results in

 subjective color experiences corresponding to various wavelengths of light.

h proposed a resonance place theory of auditory perception in which

the pitches of sound we hear are determined to a great extent on where along the basilar membrane the most vibration is occurring in response to a sound vibration.

what was the minds task

to create a reasonably accurate conception of reality from the various “signs” that it receives from the body’s sensory systems; the mind is active.

Toward the end of the 18th century, it was believed

that a person’s character could be determined by

analyzing his or her facial characteristics

 Physiognomy:

 Attempt to determine a person’s character by analyzing his/her facial features, bodily structure, and habitual patterns of posture and movement.

phrenology

The examination of the bumps and depressions on the skull in order to determine the strength and weaknesses of various mental faculties.

Faculty Psycholog

The belief that the mind consists of several powers or faculties

who is associtated with phrenology

franz jospeh gall

• first to suggest a relationship between cortical development and mental functioning.

• He was the first to distinguish the functions between gray matter and white matter in the brain.

Spurzheim

 Popularized the practice of phrenology with books and demonstrations of its uses and brought it to the US

•  Phrenology provided a way to study man scientifically, instead of just philosophically.

Formal Discipline

• A number of educators took this “mental muscle” approach by suggesting that practicing could make the faculties associated with a particular discipline stronger

Broca’s area (left frontal lobe side of the cortex)

Responsible for speech production

Wernicke’s area (left temporal lobe of the cortex)

Responsible for speech comprehension

 Gustav Fritsch (1838-1927) and Eduard Hitzig

Using electrical stimulation of brain neurons, they found:

• The cortex is not insensitive as previously thought

• sensory cortex was also discovered.

when certain area of the cortex is stimulated,

muscular movements on the opposite side of the body are elicited, thus discovering the motor cortex.

Weber

 Investigated the sense of touch and mapped out the sensitivity of touch for the entire body using the two-point threshold.

what did weber find with the two point threshold

 Sensitivity ranged from the most sensitive on the tongue to least sensitive on the back

just noticeable difference

The least amount of change necessary to notice a difference along a particular dimension between two stimuli

first quantitive law in psychology

webers law - the finding that the amount of change necessary to determine the just noticeable difference (jnd), is a constant fraction relating the stimuli

psychophysiscs

fechner ;The systematic study of the relationship between physical and psychological events