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← Genetics Lecture (continued from unit 1) Behavioral Genetics: Research Methods o Adoption studies Are adopted children more like their biological or adoptive parents? Adoptee’s traist tend to bear more similarity to their biological parents than their adopted care-givers But care giving parents influence attitudes, values, religious beliefs Problems with twin studies o Assumption of equal environments: MZ twins treated more similarly (also prenatal environment more similar) o Assumption of random mating. If people choose mates similar to themselves then DZ twins may share more than 50% of their genes People are more likely to choose people similar to them in intelligence Molecular Genetics o Classical twin study designs are only one aspect of genetics research Twin studies estimate the heritability of a trait, but molecular genetics attempts to pinpoint the effects of a particular gene Genes and personality o Williams syndrome Have trouble with visual/spatial tasks Kid with blocks, got the basic parts but not the overall picture Genetics of love o Male students slept in the same t shirt for two nights o Female students smelled the shirts and rated them for attractiveness
o Those rated most attractive were those whose immune system genetics were most compatible (i.e. immune system genetics are most dissimilar to their own) Ethics of genetic research o The potential of gene research has yet to be realized but if moving at an alarming rate o Ethics committees are struggling to keep up with the new dilemmas that arise regularly o Are the potential benefits sufficient to justify the risk ← ← Basic Anatomy of the eye ← Physiology of “seeing Color vision Feature detectors ← ← How does the eye work? Not really like a camera o Eyes don’t faithfully represent the environment around us ← What’s the different between sensation and perception? Sensation is the conversion of energy form the environment into a pattern of response by the nervous system o Process through which environmental energy converted to neural impulses is referred to as transduction Perception is the interpretation of this information Our brains determine what we see ← The eye Light enters through cornea which bends light to focus it on pupil
Convert light into electrochemical signals that feed into bipolar and then ganglion cells which carry information into the brain via the optic nerve o Ganglion cell axons converge to form the optic nerve o More rods converge on fewer bipolar cells than do cones Even a small amount of light can stimulate the bipolar cells connected to rods (great in low light) But convergence leads to imprecise information about location (poor resolution) Rods are like quantity over quality, lots of cells so you can see but it’s not as good as cones o Receptive field The region of space in which the presence of a stimulus will alter the activity of a cell Larger for rods than cones Smaller in fovea than in periphery Fovea densely filled with cones Color vision o What strikes our eyes is not color, but pulses of electromagnetic energy o The color of objects is determined by the wavelengths that they reflect Red objects reflect red (all) wavelengths and absorb all others White objects reflect all visible wavelengths Black objects absorb all visible wavelengths o The young-helmholts (trichromatic) theory Our receptors respond to three primary colors Color vision depends on the relative rate of response by the three types of cones Each type of cone is most sensitive to a specific range of electromagnetic wavelengths
Short wavelengths are seen as blue Medium wavelengths are seen as green Long wavelengths are seen as red o Trichromats have all three cones Red cones Blue cones Green cones o Dichromats have only two types of cones Color blind: can’t tell between red and green o The opponent process theory: Trichromatic theory does not account for some of the more complicated aspects of color perception Some colors we never see together We do see yellowish greens and bluish reds We don’t see reddish greens or yellows blues Experience of color after image Opponent process theory says we perceive color not in terms of separate categories but rather in a system of paired opposites Red vs. green, yellow vs. blue, white vs. black Color after images results from alternating stimulation and inhibition of neurons in the visual system A bipolar neuron that responds strongly to yellow will be inhibited by blue After you’ve stared at a yellow object your fatigued bipolar cell will behave as if it’s been inhibited and yield a sensation of blue o Sensation meets perception
← Perception: Making sense of sensation
Perception is cortical o Putting pieces of info together and interpreting it The rules that help solve the immensely difficult problem of perception Gestalt grouping principles Depth cues ← Visual Illusions Tripping up the rules that guide perception ← How to solve the problem of perception? The goal of perception: allow us to gain knowledge of our environment (what is out there?) and help guide our actions The problem of perception: for any given pattern of stimulation ← Why is perception a hard problem? Figure-ground segregation o Figure: the object of interest o Ground: the background o Sometimes simple, sometimes ambiguous The “inverse problem” o Need to extract 3-D information from a 2-D image o A 2-D image can translate into infinite 3-D realities ← Gestalt Grouping Principles Help us organize/interpret visual information
Position relative to horizon Relative clarity Texture gradient Shadow ← Binocular cues for the perception of distance Convergence o To look at an object closer by, the eyes rotate “towards each other” Divergence: o For an object farther away they rotate “away from each other” Accommodation provides a monocular depth cue Eyes separated by 2-3 inches Each receives somewhat different image of object o Two dimensional images on retina fused into a three dimensional image in brain Visual Illusions Illusion: a perceptual experience conflicting with another experience about the same object Illusions can occur for many reason, because perception (the interpretation of the world from sensory inputs) takes place at many levels in the brain and can be fooled or break down in many ways Illusions are windows into the valuable work that perception does for us all the time They’re entertaining but also real scientific tools Perception does not equal reality We adjust our perception based on our perceived viewing angle Ponzo illusions o Converging lines provide a depth cue. Experience tells us that more distant objects can only create the same sized image as a nearer one if it is actually larger Size constancy The moon illusion o The moon looks larger when it is near the horizon o Because of position relative to horizon Lightness constancy: relative luminance provides important information Rules can override explicit knowledge
← Vision
Dorsal pathway goes up Ventral pathway goes down Hierarchical processing o Damage to brain areas further along the visual information processing pathway don’t cause blindness, but an inability to process specific features of a stimulus (e.g. color, motion, etc) ← V4: Visual areas specialized for color perception There is a specialized brain area that allows you to perceive color Damage to this area results in cerebral achromatopsia Achromatopsia ← MT: visual brain area specialized for motion MT stands for Middle temporal Color vs. motion ← Akinetopsia: Motion blindness World is seen as a series of snapshots rather than as a moving image o Kind of like a strobe light Results after damage to visual brain areas specialized for processing motion (MT) ← Normally we stitch together static pictures Apparent motion ← Mishkin Discovered main pathways (dorsal and ventral) ← What vs. Where pathways What: Ventral
o Specialized for object perception and recognition (e.g. recognizing faces or objects) Where: dorsal o Specialized for spatial perception such as determining where an object is and relating it to other objects in a scene (e.g. reaching and grasping for an object) Object recognition: constancy across viewpoints Recognition by components: Biederman 1987 o Pretty old theory o Visual vocabulary of geons o Says we only see the basic shapes Multiple view recognition: Tarr (1995) o To recognize an object form different viewpoints store how it looks from many different views Different predictions o Recognition by components predicts viewpoint-independent recognition o Recognition by multiple views predicts viewpoint-dependent recognition o Problem: familiar objects have been seen from many views so no effect of viewpoint is predicted by both theories o They used abstract objects that were not common and just made up ← Faces are processed holistically Obligatory processing of “whole” face Famous people halves of faces combined o Easier to tell who they were when she split them Release from holistic effects o Misalignment
← Abnormalities in the “what” pathway
Visual agnosia: difficulty identify objects despite no problems “seeing” Prosopagnosia: difficult identifying faces despite no problems with “seeing” o Often rely on cues like hair Capgras delusion o Seeing the “meaning” in things further depends on interactions with yet other parts of the brain o The connection between the what (ventral) pathway and the amygdala Problems with the where (dorsal) pathway Spatial neglect o Woman can’t consciously see the left side ← Seeing… …is not simply viewing an image on the back of the brain …it involves a computational division of labor and analysis ← ← Why is attention necessary? It awareness were a nightclub attention would be the bouncer ← ← General Model of Attention Attention is proposed to be the gate between sensory processing and awareness o All sensory input enters the sensory memory store where it is processed pre-attentively o Some of it is selected to pass through the gate into consciousness
Feature based Only look for a feature (red when finding where’s waldo) Inattentional blindness Red cross moved across the screen Head-up display Putting the controls for pilots on the window instead of down on the dashboard Didn’t work well, they didn’t pay attention o Driving simulation study Free navigation through virtual city using steering wheel and computer screen Had to follow the flashing blue or yellow arrows Subjects were told before which to follow [selective attention is either blue or yellow depending on which you’re told to look for] Motorcycle pops out at you Either blue or yellow If the colors matched 7% collision rate, if mismatched than 34% collision o What about cell phones? People on cell phone were about the same as baseline at tracking Only 10% of people on cell phone noticed the unexpected new symbol (70% baseline did) o Conscious o Attention doesn’t lead to awareness (slide 51) Have to attend to something to be conscious of it
← Top down control selector Examples of top down and bottom up attentional selection o Bottom up selection: stimulus properties that capture your attention (ex. A flash of light) o Top down: goal driven selection of information (ex. Finding your keys on a cluttered desk) Can practice influence the capacity of attention o Attention is very limited o Green and Bavelier (2003) found that experienced action video game players had a larger visual attention capacity o Video game players identified ~4.8 items in a briefly flashed array compared to non gamers who only identified 3. Take home messages o Attention helps us deal with what could be a very overwhelming world o Attention can act to select information at different stages of processes (based on outputs of feature-detectors or more complex processing of meaning) o There are different mechanisms of attention which allow us to attend to spatial locations or stimulus features/properties ← ← What is consciousness Self-awareness: the subjective experience of ourselves as thinking and feelings beings Awareness of our environment Unconsciousness o We are aware of some mental processes but not others o Unconscious or subliminal perception can influence cognition Subliminal perception: stimuli that our sensory systems respond to but never reach the threshold of entering into consciousness ← How does the brain give rise to conscious awareness?
