Psychology Lecture Module 3 - Sensation & Preception PDF

Psychology 1100 Lecture - Week 5 Day 8: Oct 9th Sensation and Perception I: Introduction and Measurement What do we mean by sensation & perception? Sensation - the ability to detect a stimulus and, perhaps, to turn that detection into a private experience. Perception - the act of giv...

Psychology 1100 Lecture - Week 5 Day 8: Oct 9th Sensation and Perception I: Introduction and Measurement What do we mean by sensation & perception? Sensation - the ability to detect a stimulus and, perhaps, to turn that detection into a private experience. Perception - the act of giving meaning to a detected sensation Sensation and perception are central to mental life. Without them, how would we gain knowledge of the world? Perception is influenced by context What do we sense? In a word – survival. Senses – gates on the world Gates: Permit things to pass in ^signals (keep things out.) Our sense organs respond to a very restricted range of information in the world. Visible Wavelengths Audible Frequencies (Hz) Senses rely on specific energies Sensory neurons Electromagnetic energy - light (vision) Mechanical sensation (pressure, touch) (somatosensation, vestibular sensation, kinesthesis) Sound waves (hearing) Chemical compounds (olfaction, gustation) All senses use the same process to transmit information to the brain Sensory Transduction Receptors convert stimulation into electrical impulses which are sent to the brain. Recognized through a system of coding, where the coding depends on receptor source. All perception arises through electrical signals. How do we measure sensation and perception? Psychophysics: the science of defining quantitative relationships between physical and psychological events. Thresholds (like a limit) Signal detection theory Adaption Core Concepts of Sensation and Perception Psychophysics adopted several new concepts for understanding sensation and perception. Absolute threshold: minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time. Absolute thresholds for humans Sense Modality Absolute Threshold Candle flame seen at approximately 50 kilometers on a Vision clear, dark night Tick of a watch under quiet conditions at approximately 6 Hearing meters Taste Single teaspoon of sugar in approximately 7.5 liters of water One drop of perfume diffused into the entire volume of a Smell large apartment Wing of a fly or bee falling on your cheek from a distance of Touch 1 centimeter Psychophysics adopted several new concepts for understanding sensation and perception. Difference Threshold: the smallest detectable difference between two stimuli (also known as just a noticeable difference (JND) or difference limen) Weber’s Law The smallest detectable change in a stimulus is a constant proportion of the stimulus level. Weber’s law: JND is a constant fraction of the comparison stimulus - Thus, larger stimulus values have larger JNDs and small stimulus values have smaller JNDs Ernst Weber (1795-1878) Yet..perception is messy Signals are always being detected in the presence of background noise - External noise from the environment - Internal noise from your own nervous system Signal detection theory: a psychophysical that quantifies the response of an observer to the presentation of a signal in the presence of noise. Signal detection Theory Four possible stimulus/response situation in signal detection theory Signal detection theory makes a distinction between an observers’ ability to perceive a signal (sensitivity) and their willingness to report it (criterion). Sensory Adaptation Our perceptual systems are finely attuned to changes in the environment  Diminishing sensitivity to unchanging stimulus Occurs in all sensory modalities Adaptive Value Free senses to be more sensitive to changes in the environment “The psychophysicist’s microelectrode” Aftereffects Adaptation to a particular stimulus leads to reduced neural response Quickly replacing the adapted stimulus with a new stimulus can give us insight into opponent processing Psychology 1100 Lecture - Week 5 Day 9: Oct 11th Sensation and Perception II: Vision Revisiting the Cerebral Cortex Show me the light Humans only perceive a small part of the electromagnetic (EM) spectrum Light waves measured in nanometers (billionths of meter) Perceptible range (humans): ~700 nm to 400 nm The Human Eye Light waves enter the eye through the cornea - A transparent protective structure at the front of the eye Behind the cornea is the pupil - Can dilate or constrict to control the amount of light that enters the eye - Pupil size is controlled by muscles in the coloured iris that surrounds the pupil Lens Elastic structure for focusing Thinner to focus on distant objects Thicker to focus on nearby objects Retina Photoreceptors transduce light into electrical impulses Actually an extension of the brain Photoreceptors: The Rods and Cones Rods Function best in low illumination 500 times more sensitive to light than cones Found mostly in periphery to retina – though everywhere in retina except fovea Cones For colour and detail Function best in high illumination Concentrate in centre of retina Fovea (in centre of retina) contains only cones The Fovea Small area in the center of the retina Contains only cones - Excellent visual acuity - Each cone has a “private line” to a bipolar cell - What is a downside of only having cones in a fovea? Processing in the Retina Rods and cones synapse with bipolar cells, which synapse with ganglion cells Axons of ganglion cells form optic nerve Creates ‘blind spot’ where optic nerve exits from eye Brightness & Dark Adaptation Humans have a “dual visual system” Some animals only have cones (ex chipmunk) Human visual system adapted for both high and low light conditions (distribution of rods and cones) Dark adaption Becoming sensitive to low illumination takes time! Photopigment molecules need to be regenerated Progressive improvement in brightness sensitivity in low illumination Dark Adaption – Hacking the System How do we perceive colour? Trichromatic theory (Young-Helmholtz) Three types of colour receptors in retina Cones most sensitive to blue, green, red, wavelengths Visual system combines activity from these cells Colours are perceived by addictive mixture of impulses If all are equally activated – white colour is produced Problems with Trichromatic Theory Afterimages: Staring at red gives an afterimage of green Staring at blue gives an afterimage of yellow What could explain these results? Two Classic Theories of Colour Vision Dual Processes in Colour Transduction Combines trichromatic and opponent process theories 3 cone types sensitive to short (blue), medium (green), and long (red) wavelengths stimulate opponent-process reactions Opponent processes occur in ganglion cells, neurons in relay stations, and visual cortex Beyond the Eye - Impulses go from optic nerve to the thalamus to the primary visual cortex (occipital lobe) - Specific regions of retina processed in specific areas of cortex (retinotopic mapping) Visual Perception in Primary Visual Cortex Cortical Magnification Fovea has large representation in visual cortex An accidental breakthrough What and Where Pathways Inferotemporal (IT) cortex: Part of the cerebral cortex in the lower portion of the temporal lobe, important for object recognition (“what” pathway) Lesions of IT cortex can lead to anosmia Inferotemporal Cortex Receptive field properties of IT neurons Very large—some cover half the visual field (!!!) Don’t respond well to spots or lines Respond well to complex, object-level stimuli such as hands, faces, or objects Psychology 1100 Lecture - Week 6 Day 10: Oct 23th Sensation and Perception III: Hearing, Taste, Touch, Smell What energy is being transduced into neural impulses? Sound Waves - Have many physical properties that are important for perception Frequency Amplitude Waveform Shape (purity) Auditory Transduction: From Pressure Waves to Nerve Impulses Outer Ear Pinnae (part you use for earrings af sunglasses) Sound enters auditory canal Causes tympanic membrane to vibrate Middle ear Vibration causes malleus (hammer), incus (anvil), stapes (stirrup) to vibrate  Amplify sound more than 30X Oval window moves in and out Auditory Transduction: From Pressure Waves to Nerve Impulses Inner ear Cochlea A coiled, snail shaped tube about 3.5cm in length that is filled with fluid Basilar Membrane Sheet of tissue running the length of cochlea. Frequency of the way will cause maximum displacement/ movement in different parts of the basilar membrane. High frequencies near the thicket, narrower base, lower frequencies near the thinner, wider apex ←Place Theory Sound Localization When you have two ears, you can rely on subtle differences of how a sound arrives to both ears. - Slight differences in timing (interaural time differences) - Slight differences in loudness (interaural level differences) Hearing Loss In canada, an estimated 19% of adults have a mild hearing loss in the frequency ranges important for speech. Conduction deafness - mechanical system of hearing E.g. punctured eardrum, loss of function of bones of middle ear Hearing aids (which amplify the sound wave) can help Nerve deafness - damaged receptors Exposure to loud sounds can damage hair cells Hearing aids cannot help Amplitude PSA: (Dont) turn it up to 11! Amplitude Amount if compression and expansion of molecules Related to “loudness” we perceive (psychological) Decibels (dB) - logarithmic scale for intensity - each increase of 10 = doubling of perceived loudness Taste and Smell: The chemical senses Humans are (relatively) poor smellers Sensory Transduction in Olfaction Olfaction and the Limbic System What are some consequences of the direct connection of the olfactory bulb with the rest of the limbic system?’ Olfaction seems to be a powerful retrieval cue for (emotion-laden) autobiographical memories - Hippocampus - Amygdala Taste and Smell: The Chemical Senses Gustation: The Sense of Taste Chemical receptors → taste buds - several receptor cells 9000 taste buds grouped in different regions Edges and back of tongue (also roof of mouth and back of throat) Respond to four basic qualities - sweet, sour, salty, bitter - Taste buds will maximally respond to one or two qualities - Weakly respond to all taste qualities - Umami – modulator of taste, also separate quila? Individual Differences in Taste Perception “Supertasters” Same physical amount of PROP (bitter taste), as described by different individuals Taste vs. Flavour If we only have five basic taste qualities (sweet, salty, sour, bitter, umami), then how can individuals develop such incredible expertise in tasting? (ex. sommeliers picking out subtle differences in wines) What we typically call taste is actually flavour perception ← combination of taste and (retronasal) olfaction Flavour: teamwork makes the dream work The Tactile Senses At least four kinds of tactile sensations Pressure/vibration/texture Pain (nociceptors) Temperature (thermoreceptors) Touch information transduced by receptors in skin and ultimately sent to somatosensory cortex Pain Perception Free nerve endings respond to extreme stimulation (mechanical/temperature/chemical) Gate control theory - perceptual experience of pain results from opening/closing of nervous system “gates” - Other sensory input can alter how these gates operate - Descending projections from the brain can also control the flow of pain information Endorphins - Natural opiates internally produced - Endorphins exert painkilling effects by inhibiting the release of neurotransmitters involved in the pain impulses from the spinal cord to the brain Body Senses Kinesthesis - Feedback about muscles and joint positions - Receptors = nerve endings in muscles, joints, tendons Vestibular sense - The sense of body orientation or equilibrium - Semicircular canals in the inner ear - Responds to acceleration/deceleration Psychology 1100 Lecture - Week 6 Day 11: Oct 25th Sensation and Perception IV: Hearing, Taste, Touch, Smell Perception: Creation of Experience Two kinds of processing functions The Role of Attention Attention: the selective processing of some information at the expense of other information - Amplification - Filtering Perception is Selective: the Role of Attention Inattentional blindness - failure of unattended stimuli to register in consciousness - Attention acts as a set of blinders - “Looking without seeing” Gestalt Principles of Perceptual Organization “Gestalt” - pattern/shape/form - Wholes we perceive are more than sum of their parts - Early psychological movement studying mind/behaviour as a whole Suggested perception was governed by laws that determined how things were grouped together Figure-Ground Separation Attend to scenes such that information is processed as foreground, while other information is processed as background  This principle helps explain ambiguous figure perception - Two altering but equally plausible will emerge - “Switching” is possible, but simultaneous perception is not Gestalt Laws of Organization Perception and Hypothesis Testing Our perceptual worlds are ambiguous Importance of Perceptual schema Best interpretation based on knowledge Perception is influenced by Expectations: Perceptual Sets Perceptual set Readiness to perceive stimuli in a particular way Creates psychological context to use in top-down processing “Seeing is believing” Phantom Words and Phrases Depth Perception Monocular Depth Cues Illusions: False Perceptual Hypotheses Illusions Compelling but ultimately “incorrect” perceptions Erroneous perceptual hypotheses about the nature of the stimulus Due to perceptual schemas, hypotheses, sets, constancies etc Cognitive penetrability - the extent to which knowing the “trick” of the illusion diminishes the effect Our perceptual hypotheses are strongly influenced by context Cross-Cultural Research on the Perception Humans normally come into the world with the same perceptual abilities The culture one grows up in helps to determine the kinds of perceptual learning experiences people have Critical Periods in Perception Critical periods Time period during which certain experiences must occur in order for perception to develop normally Lecture Rundown