Famous psychology experiments

Famous Psychology Experiments

The Little Albert Experiment, 1920

• Conducted by Dr. John B. Watson
• Demonstrated classical conditioning, where involuntary or automatic behaviors can be learned through association
• A nine-month-old toddler, "Albert B," was used
• Humans can be conditioned to enjoy or fear something; it helps understand how irrational fears develop

Stanford Prison Experiment, 1971

• 24 male college students were assigned roles as either prisoners or guards
• It was discontinued after six days due to the participants adapting too fully to their roles, making it too dangerous

The Asch Conformity Study, 1951

• Solomon Asch, a Polish-American social psychologist, conducted it
• Conformity is the adjustment of a person's opinions or thoughts to align with those of others or normative social standards
• On average, nearly one-third of participants conformed to the incorrect majority over 12 trials
• Only 25% never conformed to the incorrect majority
• In a control group without actors, less than 1% chose the wrong answer

The Bobo Doll Experiment, 1961, 1963

• Albert Bandura conducted it
• Social learning theory suggests new behaviors are acquired through direct experience or observation
• Bandura selected 36 boys and 36 girls (ages 3-6) from Stanford University nursery and split them into three groups of 24.
• Female children acted more physically aggressive after watching a male subject than a female subject and were more verbally aggressive if the role model was female.

The Learned Helplessness Experiment, 1965

• Martin Seligman made observations on conditioning with dogs
• Subjects sometimes gave up after negative outcomes instead of seeking positive outcomes
• Learned helplessness is when subjects won't try to escape negative situations because past experiences have led them to believe they're helpless

The Milgram Experiment, 1963

• Stanley Milgram aimed to test the levels of obedience to authority
• Examined whether people would obey commands, even if conflicting with their conscience
• Participants (40 males, ages 20-50) were split into learners and teachers.
• Teachers shocked learners for incorrect word pairings, with shocks ranging from mild to life-threatening (though the learner was not actually shocked)
• Agency theory suggests people allow others to direct their actions because they believe the authority figure is qualified and will accept responsibility for the outcomes

The Halo Effect Experiment, 1977

• Richard Nisbett and Timothy Wilson followed up on a study from 50 years prior on the halo effect
• Edward Thorndike researched cognitive bias in the U.S. military
• 118 college students (62 male, 56 female) participated
• 70% of subjects rated the teacher as appealing when respectful/irritating when cold as compared to when the teacher was warm
• Cognitive bias can influence decisions, such as in job interviews or product endorsements

Introduction to Experimental Psychology

• The mind and body are separate entities operating by different principles, this is called dualism
• Rene Descartes advanced the concept of mutual interaction; the body and mind can influence each other
• Descartes argued that some ideas are innate or develop without external sensory input

Hermann von Helmholtz (1821-1894)

• Used the reaction-time experiment to study the speed of neural impulses
• Johannes Müller believed the transmission of nervous impulses was instantaneous
• Estimated the speed of nervous impulses at 50 meters per second; the speed depends on the diameter of the nerves involved
• Sensory physiology is the physiology of sense organs (eyes, ears) and the transmission of information to the brain.

Ernst Weber (1795-1878)

• Anatomist and physiologist in Leipzig, researching cutaneous sensation
• Detection difference (just-noticeable difference, or jnd) gets larger as the weight increases
• Weber's law states that the ratio of the amount of difference necessary to produce a jnd to the standard is a constant for any of the senses

Gustav Fechner (1801–1887)

• He was troubled by the translation of physical energy into psychological or mental representation
• Weber's work greatly influenced and named it Weber's law
• Fechner's elaborated version is called Fechner's law
• Also founded the discipline of psychophysics

Wilhelm Wundt (1832-1920)

• Considered himself primarily a psychologist and trained in physiology and medicine
• His Principles of Physiological Psychology was published in 1874
• Instrumental in organizing psychology as an independent discipline and establishing experimental psychology

Hermann Ebbinghaus (1850-1909)

• Hermann Ebbinghaus started experiments on human learning and memory
• He wrote the book Memory in 1885

Five Historic Scientists

• Hermann von Helmholtz (1821-1894): measured the speed of neural impulses
• Ernst Weber (1795-1878): discovered Weber's law, relating physical stimulation increase to the just-noticeable difference
• Gustav Fechner (1801-1887): extended Weber's law (Fechner's law) and founded psychophysics
• Wilhelm Wundt (1832-1920): established the first laboratory of experimental psychology in 1879
• Hermann Ebbinghaus (1850-1909): wrote Memory in 1885, showing complex mental phenomena could be studied

Summary of Four Primary Schools of Psychology

• Structuralism: Conscious experience
• Functionalism: The function of mental processes and how they help people adapt
• Behaviorism: Behavior and how it is changed under different conditions, with emphasis on learning
• Gestalt psychology: Subjective experience, with emphasis on perception, memory, and thinking

Sensation and Perception

• Sensation is an organism's first encounter with a raw sensory stimulus
• Perception is the process by which the stimulus is interpreted, analyzed, and integrated with other sensory information
• Stimulus is energy that produces a response in a sense organ; each stimulus has the strength or intensity to activate a sense organ
• Psychophysics studies the relationship between the physical nature of stimuli and the sensory responses they evoke
• Sensory adaptation is the capacity following prolonged exposure to stimuli
• Apparent decline in sensitivity to sensory stimuli is due to the inability of the sensory nerve receptors to constantly fire off messages to the brain

Vision: Shedding Light on the Eye

• Stimuli that register as light in eyes are electromagnetic radiation waves, these encounter the eye
• The cornea is a transparent, protective window that allows light to pass through
• The pupil is a dark hole in the center of the iris (colored part of the eye)
• Iris and the lens act to bend the rays of light so that they are properly focused on the rear of the eye
• The lens focuses light by changing its own thickness, a process called accommodation
• The retina is a thin layer of nerve cells at the back of the eyeball
• Rods are cylindrical
• Cones are short and thick

Adaptation

• Light adaptation occurs when moving from the dark to bright light and sensitivity decreases
• Retinal neurons undergo rapid adaptation inhibiting rod function and favoring the cone system within about one minute
• Visual accuracy and color vision improve over the next ten minutes; retinal sensitivity is lost
• Dark adaptation is the reverse of light adaptation and occurs when going from a well lit area to a dark area.

Sending the Message from the Eye to the Brain

• Before the neural message reaches the brain some initial alteration of visual information takes place
• Rods contain rhodopsin, a complex reddish-purple substance whose composition changes chemically when energized by light
• Stimulation of the nerve cells in the eye triggers a neural response that is transmitted to bipolar cells and ganglion cells
• Bipolar cells receive information directly from the rods and cones
• Ganglion cells collect and summarize visual information, which is gathered and moved out of the back of the eyeball through a bundle of ganglion axons called the optic nerve
• The opening for the optic nerve pushes through the retina causing no rods or cones to be in the area called the blind spot
• Optic nerves from each eye meet at a point roughly between the two eyes called the optic chiasm where each optic nerve then splits
• The nerve impulses coming from the right half of each retina are sent to the right side of the brain, and the impulses arriving from the left half of each retina are sent to the left side of the brain

Color Vision Theories

• Trichromatic Theory - reception of red, green, and blue colors, the ratio of each color to the other then determines the exact color
• Opponent-Process Theory - color perception depends on the reception of pairs of antagonist colors. Each receptor can only work with one color at a time so the opponent color in the pair is blocked out.
• Pairs = red green, blue-yellow, black-white (light-dark)

Color Blindness and Other Eye Conditions

• In the most common form, all red and green objects are seen as yellow
• In yellow-blue blindness, people can not tell the difference between yellow and blue, and in the most extreme case all individuals perceive no color at all
• Glaucoma cell leads to tunnel vision

Sense of Hearing

• The outer ear functions simply as a reverse megaphone, designed to collect and bring sounds into the internal portions of the ear

Sensing Sound

• Sound localization is the process the outer ears help identify the origin of
• Sound is the movement of air molecules brought about by the vibration of an object
• Auditory canal is a tube-like passage that leads to the eardrum
• The eardrum operates like a miniature drum vibrating when sound waves hit it

Anatomy of the Ear

• Middle ear: tiny chamber containing hammer, anvil, and stirrup
• The oval window is a thin membrane leading to the inner ear
• The inner ear changes the sound vibrations allowing them to be transmitted to the brain
• The cochlea is a coiled tube filled with fluid
• The basilar membrane is a structure that runs through the center of the cochlea, dividing it into an upper and a lower chamber
• The basilar membrane is covered with hair cells; when these hair cells are bent by the vibrations entering the cochlea, a neural message is transmitted to the brain
• Bone conduction helps cochlea pick up subtle vibrations that travel across bones from other parts of the head

The Six Steps in the Hearing Process

• Sound travels from the environment into the ear canal, causing the tympanic membrane (or the eardrum) to vibrate
• The eardrum vibrates according to the frequency and amplitude of the sound wave
• The sound is sent over to the ossicles, which are the bony structures in the middle ear
• The vibrations are picked up by the fluid in the cochlea; this causes the sound waves to travel even further into the ear
• The vibrations are picked up by small specialized hair cells that line the semicircular canals; hair cells at one end of the cochlea can pick up higher-frequency sounds than the hair cells on the other end of the cochlea
• The vibrations arrive at the auditory nerve, the nerve picks up the signal and transmits it to the brain where it is processed and perceived

Physical Characteristics of Sound

• What we refer to as sound is actually the physical movement of air molecules in regular, wavelike patterns
• Amplitude (Physical strength): refers to the height of a wave crest and is a measure of physical strength of sound wave
• Wavelength: The distance between successive crests; sound waves are generally described by their frequency
• Frequency determines the pitch of the sound
• Intensity refers to the difference between the peaks and valleys of air pressure in a sound wave as it travels through the air.
• Over 120 decibels becomes painful to the human ear; exposure can cause loss as the hair cells of the basilar membrane lose their elasticity and bend and flatten

Balance: The Ups and Downs of Life

• The semicircular canals of the inner ear consist of three tubes containing fluid that sloshes through them when the head moves, signalling rotational or angular movement to the brain.
• Acceleration, backward, or up-and-down motion, as well as the constant pull of gravity is sensed by the otoliths, tiny, motion-sensitive crystals within the semicircular canals.
• Semicircular canals consist of three small tubes filled with fluid
  • Posterior canal detects when the head tilts down towards the shoulder
  • Anterior canal detects when the head nods head up and down
  • Horizontal canal detects when the head shakes side to side in a no motion

The Skin Senses: Touch, Pressure, Temperature, and Pain

• Skin senses of touch, pressure, temperature, and pain. Most of these operate through nerve receptor cells located at various depths throughout the skin.
• Receptors in the skin are sensitive to touch
• Three layers of skin
  • Epidermis
  • Dermis
  • Hypodermis
• Gate-control theory receptors lead to parts of the brain related to pain; activation causes brain gate to open allow sensation of pain

How Does Gate Control Work?

• The Gate Control Theory of Pain is a mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it.
• The gate can be 'open' or the gate can be 'closed'

Sense of Smell

• The brain remember smells, and long forgotten events and memories can be brought back with an odor associated with the memory
• Women generally have a better sense of smell than men
• The receptor cells of the nose are spread across the nasal cavity.
• Responses of cells combine into recognition of a smell
• Women are able to identify their babies solely on the basis of smell just a few hours after birth
• Androsterone study showed women respond negatively to the smell except for when at risk of becoming pregnent and is acting like a phermone

Sense of Taste

• Four basic receptor cells specialize in sweet, sour, salty, or bitter flavors
• Receptor cells for taste are located in taste buds across the tongue
• The tip of the tongue is most sensitive to sweetness
• The sides of the tongue are very sensitive to sour tastes
• The rear specializes in bitter tastes
• The different taste areas on the tongue correspond to different locations in the brain
• "Super tasters" have twice as many taste receptors that makes them more sensitive

Five Common Non Experimental Approaches in Psychology

• Phenomenology is the description of an individual's immediate experience rather than external behaviors and events.
  • Phenomenology falls near the low-low end of research activities
  • Cannot be used to understand the causes of behavior and describes, but cannot explain behavior
• Empirical phenomenology or Contemporary phenomenology rely on researcher's own experiences or on experiential data provided by other sources.
  • From the researcher's self-reflection, participants' oral or written descriptions, and accounts from literature, poetry, visual art, tv, theatre and previous phenomenological research

Case Studies

• Case studies are descriptive records of a single individual's experiences or behaviors
• They are a source of inferences, hypotheses and theories
• They allow the study of rare phenomena as well as sources for developing therapy techniques
• They provide exceptions, or counter-instances, to accepted ideas, theories, or practices
• They have persuasive and motivational value like in advertising
• Field Studies nonexperimental approaches used in the field or in real-life settings.
  • Naturalistic observation observes behaviors as they occur spontaneously in natural settings, subject's responses are free to vary
  • Systematic observation uses a pre-arranged strategy for recording observations for objectivity.
• Participant-Observer Studies the researcher actually becomes part of the group being studied
• Archival Study- descriptive method in which already existing records are re-examined for a new purpose (newspapers, films, magazines etc)
• Qualitative Research- relies on words rather than numbers for the data being collected
  • Used to study phenomena that are contextual

Alternatives to Experimentation: Surveys and Interviews

• Survey Research gathers data about experiences, feelings, thoughts and motives that are hard to observe directly
• Written questionnaires and face-to-face interviews are the two common survey techniques
• Constructing surveys first to map out the research objectives and design the survey items
• Closed questions or structured questions-answered by one of a limited number of alternatives
• Open-ended questions or open questions-solicit information

Measuring Responses

• Nominal scale classifies items into two or more distinct categories on the basis of some common features
• Ordinal scale measure of magnitude in ranks measurements
• Interval scale measurement of magnitude having equal intervals between values
• Ratio scale- magnitude measurement having equal intervals between values and having an absolute zero point

Evaluating Surveys and Survey Data

• Reliability is the extent to which the survey is consistent and repeatable
  • Responses to similar questions should be consistent
  • Survey should generate very similar responses across different survey-givers
  • Survey should generate very similar responses if it is given to the same person more than once.
• Validity refers to the extent to which a survey actually measures the intended topic

Correlational & Quasi-Experimental Designs

• In a study, selected traits or behaviors of interest are measured first. correlation, between the numbers is determined
• Pearson Product Moment Correlation Coefficient (r) is the most commonly used procedure
  • Positive relationship / direct relationship-The relationship measures that increase one shows increase in the other
  • Negative relationship / inverse relationship-The relationship between two variables shows the the increase cause decrease one another
  • No relationship-when r is near zero
• Linear Regression Analysis estimates a score on one measured behavior from a score on the other when two behaviors are strongly related
  • Multiple Correlation- inter-correlations among 3+ behaviors
  • Multiple Regression Analysis- technique that uses a regression equation to predict the score of one behaviour from scores on the other related behaviours
  • Factor Analysis- used to see degree of relationship among traits-determines factors and sorts items according to their groupings.
• Causal Modelling creating and testing causation models
  • Path analysis, subjects are measured on several related behaviors
• Cross-lagged Panel Design measures set of behaviors at different times and correlations show casual direction
• Quasi-Experimental Designs have manipulation without treatment conditions
• Ex Post Facto Studies- A study examines effects of pre-existing subject characteristics
• Nonequivalent Groups Design- A design that compares treatment conditions on pre-existing groups of participants
• Longitudinal Design- group that gets followed and measured at different points in time
• Cross-sectional Study- a method that measures different groups of subjects at different stages who are at different stages
• Pretest/Posttest Design- A research design used to assess whether an event alters behavior