3 How do we take in information? A sense is a system that translates information from outside the nervous system into neural activity.Messages from senses are called sensationsFor example, vision is the system through which the eyes convert light into neural activity. This tells the brain something about the source of the light (brightness) or about the objects from which the light is reflected (round, red, etc).
4 Elements of a Sensory System Energy (light, sound waves, etc) contains info about the worldAccessory Structures (lens, ear, etc) modify energy.Transduction- the process of converting incoming energy into neural activity through sensory receptorsSensory nerves transfer the coded activity to the Central Nervous System.Thalamus processes and relays the neural response (except in smell).Cortex receives input and produces the sensation and perception
6 How does physical energy get converted into neural activity? CODING - translation of the physical properties of a stimulus into a pattern of neural activity that specifically identifies those physical properties.Doctrine of Specific Nerve Energies - stimulation of a particular sensory nerve provides codes for that one sense, no matter how the stimulation takes placeTemporal Code - involves changes in the timing of the neurons firing. Ex: A bright light will cause some neurons in the visual system to fire faster than a dim light.Spatial Code - the location of the firing neurons provides information about the stimulus (tells us where the sensation is coming from).
7 HEARINGSound is a repetitive fluctuation in the pressure of a medium, such as air.In a place like the moon, which has almost no atmospheric medium, sound cannot existWhen you speak, your vocal cords vibrate, producing fluctuations in air pressure that spread as waves. A wave is a repetitive variation in pressure that spreads out in 3 dimensions.
8 Physical Characteristics of Sound Amplitude- (intensity) difference in air pressure from the baseline to the peak of a wave.Wavelength- the distance from one peak wave to the next.Frequency- number of complete waves, or cycles, that pass by a given point in space every second. Described in a unit called hertz, (Hz). 1 cycle per second is 1 hertz
10 Psychological Dimensions of Sound What do we actually hear? Loudness- determined by amplitude. Greater amplitude = Louder soundsPitch- how high or low a tone sounds. Determined by frequency.High frequency = High PitchLow Frequency = Low PitchTimbre- (pronounced “tamber”) is the quality of the sound
11 The EarAuditory accessory structures modify sound waves before information affects neural signalsPinna – crumpled part of ear that funnels sound through the ear canalTympanic Membrane – eardrum – tightly stretched membrane in the middle ear where sound waves strikeVibrations of the tympanic membrane are transferred through 3 tiny bones - malleus (hammer), incus (anvil), stapes (stirrup)Sound Waves 1
12 Auditory Transduction After sound passes through the oval window, it enters the inner ear or cochlea - this is where transduction occursThe basilar membrane forms the floor of this long tubeSound waves bend hairs of the organ of Corti – a group of cells which rest on the membraneHair cells connect with fibers from the auditory nerve, a bundle of axons that goes into the brainSound Waves 2Figure 4.4: The Cochlea
13 Auditory Pathways Auditory nerve brainstem thalamus The information coded in the activity of auditory nerve fibers is conveyed to the brain and processed furtherInformation is relayed from the auditory nerve to an area of the cerebral cortex called the primary auditory cortexVarious aspects of sound processed in different regions of auditory system.Certain parts of auditory cortex process certain types of sounds.
16 Sensing PitchDifferent people may experience the “same” sound as different pitches.Pitch-recognition abilities influenced by genetics.Cultural factors are also partly responsible for the way in which a pitch is sensed.
17 Locating SoundsDetermined partly by the very slight difference in when sound arrives at each ear.The brain also uses information about the difference in sound intensity at each ear.
18 Coding Intensity and Frequency The more intense the sound, the more rapid the firing of a given neuron.Frequency appears to be coded in two ways: place theory and frequency-matching theory
19 Coding Frequency: Place Theory Sounds produce waves that move down the basilar membrane.Where the wave peaks depends on the frequency of the sound.Hair cells at a particular place on the membrane respond most to a particular frequency.
20 Coding Frequency: Frequency Matching Theory Firing rate of an auditory nerve matches a sound wave’s frequency.Sometimes called the “volley theory” of frequency coding.
21 Vision Light – electromagnetic radiation Visible light has a wavelength from just under 400 nanometers to 750 nanometersLight intensity –How much energy the light containsDetermines the brightness of lightLight Wavelength –The difference between peaks in light wavesDetermines what color we see
25 Accessory Structures of the Eye Cornea – curved, transparent layer through which light rays enter the eyePupil – opening in the eye through which light passesIris – colorful part of the eye which adjusts the amount of light entering the eyeLens – bends rays, focusing them on the retinaRetina – Surfaces at back of the eye onto which the lens focuses light rays
27 VisionAccommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retinaAcuity- the sharpness of visionNearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retinaFarsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina
30 Converting Light into Images Visual transduction is the conversion of light energy into neural activity.Conversion done by photoreceptors in the retina.Two main types of photoreceptors: Rods and cones.
31 Rods and Cones Rods Cones peripheral retina detect black, white and graytwilight or low lightConesnear center of retinafine detail and color visiondaylight or well-lit conditions
32 Interactions in the Retina Photoreceptor cells connect to bipolar cells and then to ganglion cellsAxons of the ganglion cells form the optic nerve, which extends out of the eye and into the brainEach neuron of a sensory system has a receptive field – part of the retina and the region of the environment to which that cell responds
33 Figure 4.11: Center-Surround Receptive Fields of Ganglion Cells
34 Figure 4.12: The Hermann Grid The cell whose receptive field includes the space at the intersection has more whiteness shining on its inhibitory surround than the cell whose receptive field is just to the right of the intersection. The output of the intersection cell will be lower than that of the one on the right, creating the impression of a shadow.
35 Visual PathwaysAxons from ganglion cells converge as a bundle of fibers called the optic nerve and exit the eyeball at one spotThe exit point has no photoreceptors and is insensitive to light creating a blind spotAbout ½ the fibers of the optic nerve cross over to the opposite side of the brain at the optic chiasm (part of the bottom surface of the brain)
36 Visual Pathways con’tAxons from most of ganglion cells in retina form synapses in the thalamus, in a specific region called the lateral geniculate nucleus (LGN)Neurons in the LGN relay the visual input to the primary visual cortex, located in the occipital lobes in the back of the brain
38 Visual Representations Receptive fields of neurons are characterized by parallel processing and hierarchical processingParallel Processing of visual properties: Brain conducts separate kinds of analysis simultaneously on the same information.The “what” systemThe “where” systemHierarchical Processing of visual properties:Individual cells in the visual cortex receive input from several LGN neurons.Cortical cells respond to specific features of objects in the visual field – Feature detectorsLight Conversion
39 Seeing ColorHue – color determined by the dominant wavelength in the mixture of the light (excludes black, white, gray)Saturation – purity of a colorBrightness – overall intensity of the wavelengths that make up light
40 Visual Information Processing Trichromatic (three color) TheoryYoung and Helmholtzthree different retinal color receptors
41 Trichromatic Theory of Color Any color can be produced by mixing pure lights of blue, green, and red.There are three types of cones, each most sensitive to particular wavelengths.Ratio of the activities of the three types of cones indicates what color is sensed.
42 Opponent-Process Theory Ewald HeringEach of the three color sensitive elements are organized as pairs, where each pair member opposes, or inhibits, the otherRed-GreenBlue-YellowBlack-White
49 Olfactory System Employs about 1,000 different types of receptors. Only sense that does not send its messages through the thalamus.Processing in several brain regions including frontal lobe and amygdalaStrong relationship between olfaction and emotional memory
50 Olfactory System (cont’d.) Only sense that does not send its messages through the thalamus.Pathways from olfactory bulb sends information on for further processing in several brain regions.Including frontal lobe and amygdala.Strong relationship between olfaction and emotional memory.
51 PheromonesChemicals released by one animal, and when detected by another, can shape the second animal’s behavior or physiology.Role of pheromones in humans not clear
52 Age, Sex and Sense of Smell WomenMenAge Group432Numberof correctanswersWomen and young adultshave best sense of smell
53 Smell, Taste, and FlavorSmell and taste act together to form system known as flavor.Tastes and odors can prompt strong emotional responses.Nutritional state can affect taste and flavor of food and motivation to eat particular foods.Flavor includes other characteristics of food.
54 Somatic Senses and the Vestibular System Somatosensory systems are spread throughout the bodySomatic senses include:Skin senses of touch, temperature, and painKinesthesiaVestibular system tells the brain about the position and movement of the head
55 Touch Energy detected is physical pressure on tissue. Many nerve endings in the skin act as touch receptors.Touch is both an active and passive sense.Changes in touch provide most important sensory information.
56 Coding of Touch Information Intensity of the stimulus is coded by:Firing rate of individual neurons andThe number of neurons stimulated.Location is coded by the location of the neurons responding to the touch.
57 TemperatureSome of the skin’s sensory neurons respond to a change in temperature.“Warm” and “cold” fibersSensations of touch and temperature sometimes interact.Stimulation of the touch sense can have psychological and physiological effects.
58 Pain Pain provides information about impact of world on body. Information-carrying aspect of pain very similar to that of touch and temperature.Two types of nerve fibers carry pain signals from skin to the spinal chord.Cerebral cortex plays role in the experience of pain.
60 Modulating Pain Gate Control Theory theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain“gate” opened by the activity of pain signals traveling up small nerve fibers“gate” closed by activity in larger fibers or by information coming from the brainNatural AnalgesicsSerotoninEndorphins
61 Proprioceptive Senses Sensory systems that provide information to the brain about:The position of the body.What each of part of the body is doing.Vestibular sense indicates the position of the head in space and its general movements.Sense of balance.
62 Vestibular Sense Organs: Neural connections to: Vestibular sacs OtolithsSemicircular canalsNeural connections to:The cerebellumThe autonomic nervous systemThe eye muscles
63 KinesthesiaSense that indicates where the parts of the body are with respect to one another.Necessary guide for movement.Kinesthetic information comes primarily from the joints as well as muscles.
65 Three Approaches to Perception Computational – tries to determine the computations that a machine would have to solve perceptual problemsConstructivist – reality is constructed from fragments of sensory informationEcological – environment contains most of the information needed to form perceptions
66 PsychophysicsDescribes the relationship between the physical energy in the environment and the psychological experience of that energyAbsolute Threshold – the minimum detectable amount of environmental energy a sensory system can detect
68 Signal-Detection Theory Sensitivity – a person’s ability to pick out a particular stimulus or signalResponse Criterion – a person’s willingness or reluctance to say that a stimulus is presentSignal-Detection Theory – model of our personal sensitivity and response criterion combined to determine whether or not a near-threshold stimulus has occurred
70 Judging Differences Between Stimuli Difference Threshold or Just-Noticeable Difference (JND)JND determined by two factors:How much of a stimulus was there to begin with?Which sense is being stimulated?Click the link below to see how JND impacts the consumer world:
71 Weber’s Law Weber’s Constant Law States That JND = KI K is the Weber’s constant for a particular sense.I is the amount, or intensity, of the stimulus.The smaller K is, the more sensitive a sense is to stimulus differences
72 Magnitude EstimationMagnitude estimation is how our perception of stimulus intensity is related to actual stimuli strengthFechner’s LawConstant increases in physical energy will produce smaller increases in perceived magnitudeSteven’s Power LawDescribes a wider range of sensations
73 Perceptual Illusions Illusion – incorrect perception of a stimulus Delusion – a false beliefHallucination – a perception in the absence of a stimulus
78 Basic Processes in Perceptual Organization Figure-Ground OrganizationPerceptual apparatus picks out some objects to be figures, while others are less relevant in the backgroundGroupingInherent properties of the stimulus environment lead people to group them togetherGrouping PrinciplesProximity--group nearby figures togetherSimilarity--group figures that are similarContinuity--perceive continuous patternsClosure--fill in gapsConnectedness--spots, lines, and areas are seen as unit when connectedSynchrony – occur at the same timeCommon region – located within some boundaryConnectedness – connected by other elements
83 Perceptual Organization Likelihood PrincipleWe perceive objects in the way that experience tells us is the most likely physical arrangement (consistent with Constructivism)Simplicity PrincipleWe organize stimulus elements in a way that gives us the simplest possible perception
85 Perception of Location and Distance Two-Dimensional Location – uses an equation that takes information about where an image strikes the retina and adjusts it based on information about movement of your eyes and headVisual dominance – bias toward using visual information when it conflicts with information from other senses
86 Depth PerceptionOur ability to perceive distance, allowing people to experience the world in three-dimensionsInterposition – closer objects block the view of things further awayRelative Size – the object producing a larger image on the retina is perceived as closerHeight in the Visual Field – more distant objects are higher in the visual fieldTexture Gradient – graduated change in texture – less detailed as distance increasesLinear Perspective – the closer together 2 converging lines are, the greater the perceived distanceClarity, Color, Shadow – distant objects appear hazierMotion Parallax – objects closer appear to move rapidly, while those distant appear motionless
87 Figure 5.10: Stimulus Cues for Depth Perception
88 Cues Based on Physiology Accommodation – muscles surrounding the lens either tighten (to focus on close objects) or relax (to focus on distant objects)Convergence – each eye rotates inward to see closer objectsBinocular Disparity – the difference between the two retinal images of an object provides distance cues
93 Perception of MotionLooming – a rapid expansion in the size of an image so that it fills the retina and is perceived as an approaching objectStroboscopic Motion – our tendency to perceive motion through a series of flashing rapid light
94 Perceptual ConstancyThe perception of objects as constant in size, shape and colorSize Constancy – occurs as objects move closer or farther awayShape Constancy – occurs as an object appears the same, even though the shape of its retinal image changesBrightness Constancy – occurs so that no matter how the amount of light striking an object changes, its perceived brightness remains constant
98 Recognizing the Perceptual World The brain analyzes the incoming pattern of the stimulus and compares that pattern to information stored in the memoryTop-down processing – guided by knowledge and expectationsOur experiences create schemas, or mental representations of what we know about the worldBottom-up processing – relies on specific, detailed information from sensory receptors that are integrated and assembled into a whole
99 Parallel Distributed Processing Models (PDP) Units in a network operate parallelsimultaneouslyEach element is connected to all other computational elementsRecognition occurs as a result of the simultaneous operation of connected units
100 AttentionThe process of directing and focusing certain psychological resources to enhance perception, performance, and mental experience