{"id":4434,"date":"2018-10-07T00:27:18","date_gmt":"2018-10-07T04:27:18","guid":{"rendered":"https:\/\/www.amyork.ca\/academic\/zz\/?p=4434"},"modified":"2018-10-07T00:47:33","modified_gmt":"2018-10-07T04:47:33","slug":"sensation-and-perception","status":"publish","type":"post","link":"https:\/\/www.amyork.ca\/academic\/zz\/sensation-and-perception\/sensation-and-perception\/","title":{"rendered":"Sensation and perception"},"content":{"rendered":"<ul>\n<li>Sensation: the ability to detect a stimulus and, perhaps, to turn that detection into a private experience<\/li>\n<li>Perception: the act of giving meaning to a detected sensation<\/li>\n<li>Condillac: mental life relies on information from our senses<\/li>\n<\/ul>\n<p><em>Methods used in the study of the senses<\/em><\/p>\n<ul>\n<li>Thresholds<\/li>\n<li>Scaling: measuring private experience o Quale: in philosophy, a private conscious experience of sensation or perception<\/li>\n<li>Signal detection theory \u2013 measuring difficult decisions<\/li>\n<li>Sensory neuroscience<\/li>\n<li>Neuroimaging \u2013 an image of the mind<\/li>\n<\/ul>\n<p><em>Thresholds and the dawn of psychophysics<\/em><\/p>\n<ul>\n<li>Dualism: the idea that the mind has an existence separate from the material world of the body<\/li>\n<li>Materialism: the idea that the only thing that exists is matter, and that all things, including the mind and consciousness, are the results of interactions between bits of matter<\/li>\n<li>Panpsychism: the idea that the mind exist as a property of all matter, that is, that all matter has consciousness (Fechner)<\/li>\n<li>Psychophysics: the science of defining quantitative relationships between physical and psychological (subjective) events (Fechner)<\/li>\n<li>Two-point touch threshold: the minimum distance at which two stimuli are just perceptible as separate (Weber)<\/li>\n<li>Just noticeable difference\/ difference threshold: the smallest detectable difference between two stimuli, or the minimum change in a stimulus that enables it to be correctly judged as different from a reference stimulus (Weber)<\/li>\n<li>Weber\u2019s law: the principle describing the relationship between stimulus and resulting sensation that says the JND is a constant fraction of the comparison stimulus (e.g. 1:100 for length, 1:40 for weight) o Clear objective measurement, we know how much the stimulus varied and the observer can either tell that it changed or not<\/li>\n<li>Fechner\u2019s law: a principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation(S) increases proportionally to the logarithm of the stimulus intensity(R) (S = k log R) o Describes the relationship between mind and matter\n<ul>\n<li>The smallest detectable change in a stimulus can be considered as a unit of the mind, because this is the smallest bit of change that is perceived<\/li>\n<li>Assumes that all JNDs are perceptually equivalent, which turns out to be incorrect<\/li>\n<\/ul>\n<\/li>\n<li>Absolute threshold: the min amount of a stimulation necessary for a person to detect a stimulus 50% of the time<\/li>\n<\/ul>\n<p>Detected 50% of the time due to the variability in the nervous system, stimuli near the threshold will be detected sometimes and missed other times \u2192 there is no hard boundary<\/p>\n<p><em>Psychophysical methods <\/em><\/p>\n<ul>\n<li>Method of constant stimuli: a psychophysical method in which many stimuli ranging from rarely to almost always perceivable, are presented one at a time and participants respond to each presentation: yes\/no or same\/different<\/li>\n<li>Method of limits: a psychophysical method in which the particular dimension of a stimulus, or the difference between two stimuli, is varied incrementally until the participant responds differently o Tones are presented in increasing or decreasing intensity; increasing: report when you first hear the tone; decreasing: report when the tone is no longer heard. The threshold is set at the average of the crossover points<\/li>\n<li>Method of adjustment: a method of limits in which the participant controls the change in the stimulus<\/li>\n<\/ul>\n<p><em>Scaling methods and supertasters<\/em><\/p>\n<ul>\n<li>Magnitude estimation: a psychophysical method in which the participant assigns values according to perceived magnitudes of the stimuli o Steven\u2019s power law: a principle describing the relationship between stimulus and resulting sensation that says the magnitude of subjective sensation(S) is proportional to the stimulus magnitude(I) raised to an exponent(b) ( S = aI<sup>b <\/sup>)<\/li>\n<li>Measures subjective ratings, and we can check whether these are reasonable and consistent but there is no way of knowing whether they are objectively right or wrong<\/li>\n<li>Cross-modality matching: the ability to match the intensities of sensations that come from different sensory modalities. This ability enables insight into sensory differences. For example, a listener might adjust the brightness of a light until it matches the loudness of a tone, the relationship between modalities appears to be similar across individuals<\/li>\n<\/ul>\n<p><em>Signal detection theory <\/em><\/p>\n<ul>\n<li>Signal detection theory: a psychophysical theory that quantifies the response of an observer to the presentation of a signal in the presence of noise (internal noise, the static in your nervous system). Measures obtained from a series of presentations are sensitivity (d\u2019) and criterion of the observer o Criterion: an internal threshold set by the observer. If the internal response is above the criterion, the observer gives one response (yes) and below the criterion the observer gives another response (no)<\/li>\n<li>Correct rejection, hit, false alarm, miss o Sensitivity: a value that defines the ease with which an observer can tell the difference between the presence and absence of a stimulus or the difference between stimulus 1 and stimulus 2 (d\u2019 or d-prime)<\/li>\n<\/ul>\n<p>Receiver operating characteristic (ROC) curve: the graphical plot of the hit rate as a function of the false-alarm rate. If these are the same, points fall on the diagonal, indicating that the observer cannot tell the difference between the presence and absence of a signal. As the observer\u2019s sensitivity increases, the curve bows upward toward the left corner, that point represents the perfect ability to distinguish signal from noise (100% hits, 0% false alarms). Figure 1.14 page 14<\/p>\n<p><em>Fourier analysis<\/em><\/p>\n<ul>\n<li>Sine wave:\n<ul>\n<li>In hearing: a pure tone: a waveform for which variation as a function of time is a sine function<\/li>\n<li>In vision: a pattern for which variation in a property like brightness or colour as a function of space is a sine function<\/li>\n<\/ul>\n<\/li>\n<li>Period or wavelength: the time (or space) required for one cycle of a repeating waveform<\/li>\n<li>Phase: the relative position to a fixed marker o In hearing: the relative time of a sine wave o In vision: the relative position of a grating<\/li>\n<li>Fourier analysis: a mathematical procedure by which any signal can be separated into component sine waves at different frequencies. Combining these sine waves will reproduce the original signal o Sounds: changes in pressure across time\n<ul>\n<li>Spatial frequencies: images can be broken down into components that capture how often changes from light to dark occur over a particular region in space, spatial frequencies are defined as the number of these light\/dark changes across one degree of a person\u2019s visual field<\/li>\n<li>Cycles per degree: the number of pairs of dark and bright bars per degree of visual angle<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><em>Sensory neuroscience and the biology of perception<\/em><\/p>\n<ul>\n<li>Doctrine of specific nerve energies: states that the nature of sensation depends on which sensory fibres are stimulated, not on how fibres are stimulated (M\u00fcller) o We are only aware of the activity of our nerves, we cannot be directly aware of the world itself -Cranial nerves:\n<ul>\n<li>Olfactory (I): smell \u2192 sensory o Optic (II): vision \u2192 sensory o Oculomotor (III): all eye muscles except superior oblique and lateral rectus \u2192 motor o Trochlear (IV): superior oblique muscle \u2192 motor o Trigeminal (V): face, sinuses, teeth \u2192 sensory and motor o Abducens (VI): lateral rectus muscle \u2192 motor o Facial (VII): tongue, soft palate \u2192 sensory and motor o Vestibulocochlear (VIII): spatial orientation, balance, hearing \u2192 sensory o Glossopharyngeal (IX): posterior tongue, tonsils, pharynx, pharyngeal muscles \u2192 sensory and motor<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Vagus (X): heart, lungs, gastrointestinal tract, bronchi, tranchea, larynx \u2192 sensory and motor<\/p>\n<ul>\n<li>Spinal accessory (XI): sternomastoid and trapezius muscles \u2192 motor o Hypoglossal (XII): tongue muscles \u2192 motor<\/li>\n<\/ul>\n<ul>\n<li>Polysensory: as processing extends beyond primary areas, information of more than one sense is being combined in some matter<\/li>\n<li>Vitalism: the idea that there is a force in life that is distinct from physical entities (M\u00fcller) o Helmholtz: all behaviour should be explained by only physical forces: the activity of neurons obeys normal rules of physics and chemistry, the speed with which neurons transmit their signals can be measured<\/li>\n<\/ul>\n<p><em>Neural connections<\/em><\/p>\n<ul>\n<li>Synapse (Cajal, Sherrington)<\/li>\n<li>Exhibitory versus inhibitory activity \u2192 chemical instead of electrical in the synapse (Loewi)<\/li>\n<li>Neural firing is electrochemical: voltage increases along the axon are caused by changes in the membrane of the neuron that permit positively charged sodium ions (Na<sup>+<\/sup>) to rush very quickly into the axon from outside. Then the membrane very quickly changes again in a way that pushes positively charged potassium ion (K<sup>+<\/sup>) outside the axon, restoring the neuron to its initial resting voltage (Hodgkin and Huxley)<\/li>\n<\/ul>\n<p><em>Neural firing: populations of neurons<\/em><\/p>\n<ul>\n<li>CT scan (Computerized Tomography): a narrow beam of x-rays creates a series of brain slices \u2192 static image<\/li>\n<li>PET scan (Positron Emission Tomography): radioactive tracers are injected into the blood stream together with glucose, radioactive glucose goes to specific brain regions due to several activities.<\/li>\n<li>fMRI (functional Magnetic Resonance Imaging): magnetic fields are used to track the iron in blood, to monitor increases in blood flow to the brain.\n<ul>\n<li>BOLD: blood oxygen level-dependent<\/li>\n<\/ul>\n<\/li>\n<li>MEG (MagnetoEncephaloGraphy): just as fMRI but with time frame<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>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 Condillac: mental&hellip; <a class=\"continue\" href=\"https:\/\/www.amyork.ca\/academic\/zz\/sensation-and-perception\/sensation-and-perception\/\">Continue Reading<span> Sensation and perception<\/span><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[112],"tags":[],"_links":{"self":[{"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/posts\/4434"}],"collection":[{"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/comments?post=4434"}],"version-history":[{"count":0,"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/posts\/4434\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/media?parent=4434"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/categories?post=4434"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.amyork.ca\/academic\/zz\/wp-json\/wp\/v2\/tags?post=4434"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}