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Sensation: Thresholds and Psychophysics The intensity at which you "lose" and regain the tone is your absolute threshold for that particular tone. Weber defined the absolute threshold as the intensity at which the stimulus was detected on 50% of trials. The difference threshold is the average of the two differences between the comparison stimuli and the standard. users.ipfw.edu /abbott/120/thresholds.html   (910 words)

Absolute Threshold   (Site not responding. Last check: 2007-10-09) When measuring the photopic spectral sensitivity by the absolute threshold method it is critical that the stimulus fall within the rod free area of the fovea. Because one is dealing with absolute threshold the stimuli necessarily have to be presented in a dark field. As it turns out, an absolute threshold spectral sensitivity function is nearly the same as a brightness matching function, but rather different than the CIE modified photopic luminous efficiency function which is based mostly on flicker photometry. www.yorku.ca /eye/absothre.htm   (165 words)

Absolute threshold - Wikipedia, the free encyclopedia An absolute threshold is the minimum amount of stimulation required for a person to detect a stimulus fifty percent of the time. A difference threshold is the amount of change necessary for an observer to report 50% of the time that a stimulus has changed. The difference threshold occurs where I am able to determine that the color has changed 50% of the time. en.wikipedia.org /wiki/Absolute_threshold   (195 words)

Hoikkala and Aspi (1993) T wo of these, threshold and absolute choice, are based on an internal standard, and are commonly united under the title of absolute choice (Zuk et al. Under a threshold choice [Lande's (1981) "psychophysical preference" and Maynard Smith's (1987) "directional preference"] all females prefer a male with a large value of z, although there may be variation among the females in the degree of discrimination. To determine the threshold under which the females do not accept the male as their mate, we first studied the female acceptance while she was courted by a single normal or wing-manipulated male. www.pitt.edu /~kilpatri/hoik.htm   (4569 words)

Night Vision; The Terminal Visual Threshold When the eye is light-adapted to the high level of illumination found outdoors on a bright day and the absolute threshold is measured immediately, it will be as much as 10,000 times greater then the value obtained if the eye has been resting in complete darkness for a period of thirty or forty minutes. Those so disqualified seldom if ever showed symptoms other than a relatively high absolute terminal threshold, and their reduced sensitivity must be taken as the consequence of the normal variability in the density in the retinal rods and the efficiency of the process whereby rhodopsin, the visual purple, is regenerated. Since the intensity of light delivered by the instrument may shift considerably from the prescribed values, with consequent erroneous measurement of the threshold, leading to an incorrect diagnosis of nyctalopia or a failure to detect it, the instrument must be calibrated at regular intervals. web.utk.edu /~wverplan/biblio10.html   (3840 words)

Dynamic bit allocation apparatus and method for audio coding - Patent 6308150 The masking absolute threshold of a given unit is selected from the highest among the absolute threshold, the low-band masking absolute threshold and the high-band masking absolute threshold computed on the unit. Thus, the minimum absolute threshold selected from the four long block units is used to represent the adjusted absolute threshold of the four short block units. Therefore, as the final processing result, the highest masking threshold is selected from among the absolute threshold (qthreshold [u.sub.md ]) of the masked unit u.sub.md, the upper-slope masking effect (mask_effect.sub.(upper-slope)) and the lower-slope masking effect (mask_effect.sub.(lower-slope)) to represent the level of the masking absolute threshold (qthreshold [u.sub.md ]) of the masked unit u.sub.md. www.freepatentsonline.com /6308150.html   (10726 words)

Absolute threshold of hearing - Wikipedia, the free encyclopedia (via CobWeb/3.1 planetlab2.cs.umd.edu)   (Site not responding. Last check: 2007-10-09) The absolute threshold of hearing (ATH) is the minimum sound amplitude (level or strength) of a pure tone that the average ear with normal hearing can hear in a noiseless environment. The threshold of pain is the SPL beyond which sound becomes painful for the average human listener. The absolute threshold of hearing represents the lowest curve amongst the set of equal-loudness contours, with the highest curve representing the threshold of pain. en.wikipedia.org.cob-web.org:8888 /wiki/Absolute_threshold_of_hearing   (372 words)

[No title]   (Site not responding. Last check: 2007-10-09) Finally, thresholds may represent a subject's systematic tendency to supply the same response or a different response each time, therefore, the same number of ascending and descending trials should be included and the starting point should be systematically varied (Dember and Warm, 1979). Secondly, the use of the absolute threshold as a starting point may not be judicious because the measurement of the absolute threshold, as Dember and Warm (1979) state, is "itself open to serious question." Finally, the assumption that all the jnds are subjectively equal in the magnitude scale continuum has not been supported by research. The lower limit of sensitivity for the ear seems to be determined by the sound of blood rushing through the tiny vessels in the middle and inner ear, or perhaps be the random noise generated by motion of the air molecules where the upper limit is determined by the stimulus intensity that produces pain. www.medibolt.com /users/rikr/GrokBox/rawmater/perception.htm   (12910 words)

Randomized Stimuli It has often been found that the sequence of responses to repeated stimuli having the same brightness near the absolute threshold is not random, but exhibits a serial correlation (1, 2, 6, 7, 8). Absolute threshold functions for each of the four Ss, determined without regard to the preceding response or stimulus, are shown in Figure 1. The similarity between ascending and descending thresholds constructed from the present data suggests that one-step dependence between trials is not the source of this difference. web.utk.edu /~wverplan/biblio30.html   (2620 words)

Webvision: Light and Dark Adaptation The stimulus is increased in luminance until detection threshold is reached against the background (figure 10) Therefore, the independent variable is the luminance of the background and the dependent variable is the threshold intensity or luminance of the incremental test required for detection. As background luminance is increased, the curve remains constant (and equal to the absolute threshold). In fact, the increase in threshold should be proportional to the square root of the background luminance; hence the slope of one half in a log-log plot. webvision.med.utah.edu /light_dark.html   (2369 words)

Psychophysics Encyclopedia of Psychology - Find Articles   (Site not responding. Last check: 2007-10-09) Absolute threshold: as the stimulus strengthens from the undetectable, the point at which the person first detects it. Thresholds can also be ascertained through the method of constant stimuli. Rather than try to identify a single point for the threshold, psychophysicists who employ the signal detection theory have developed ways to measure an observer's sensitivity to stimuli in ways that go beyond the simple concept of the threshold. www.findarticles.com /p/articles/mi_g2699/is_0002/ai_2699000278   (604 words)

REFLECTIONS ON THE FIELD Despite the relative clarity that a 1,000 annual death threshold offers, I would argue that it is not realistic or constructive (given the paucity of data) to constrain ourselves by such a stringent criterion. A related concern is often expressed with reference to the arbitrariness of the 1,000 death threshold. The present threshold of 1,000 deaths may actually be leading us to over-sample conflicts in large countries. mailer.fsu.edu /~whmoore/cps/newsletter/june2001/Sambanis.html   (2256 words)

Long-Range Validity of Threshold Laws in Inner-Shell Photodetachment A threshold law describes the dependence of a reaction yield near a reaction threshold. A threshold law mathematically describes the reaction yield as the energy varies near the threshold. For ionization of an atom, for example, the threshold is the minimum energy needed to eject an electron, and the threshold behavior of the ionization depends only on the Coulomb (electrical) attraction between the positively charged nucleus and negatively charged electron. www-als.lbl.gov /als/science/sci_archive/124threshold.html   (1184 words)

constant_stimuli the absolute threshold) or to determine the smallest difference between two stimuli that can be perceived (i.e. For each stimulus, the observer reports whether it was perceived (when determining the absolute threshold) or whether a difference was perceived (when determining the difference threshold). The threshold can be read from the X axis where this line meets its. plato.acadiau.ca /Courses/psyc/McLeod/2023Research/constant-STD.htm   (459 words)

[No title] Threshold: The amount of change in a stimulus ((() to produce a just noticeable difference in perception Differential Sensitivity: Relationship between the difference threshold for the intensity and the intensity of a stimulus. Absolute Threshold: For each presentation, the subject responds as to whether they perceived the stimulus, ‘YES’; or did not perceive stimulus, ‘NO’. The subject is asked to adjust the level of Co to St. Record the average final adjustment position for each trial PSE is mean adjustment position Difference Threshold is defined as the standard deviation of the adjustment positions. filebox.vt.edu /t/thdavis/HUMANINF.doc   (1193 words)

Sensation in Psychology 101 at AllPsych Online The absolute threshold is the point where something becomes noticeable to our senses. The absolute threshold is therefore the point at which a stimuli goes from undetectable to detectable to our senses. The difference threshold is the amount of change needed for us to recognize that a change has occurred. allpsych.com /psychology101/sensation.html   (563 words)

Chapter 2 Flashcards Absolute Threshold: Amount of stimulus we need to consciously notice the stimulus. Difference Threshold: Amount of change in a stimulus needed for us to notice a change in the stimulus. The absolute threshold for light is a candle on a clear night 30 miles away. uhaweb.hartford.edu /MISOVICH/ch3flash.htm   (330 words)

Contrast Lightcurves Instead a constant relative threshold is chosen throughout, as a number of standard deviations above the mean for the (invariably different) standard deviation and mean of each image. If the same absolute threshold intensity is used in both images, fewer pixels will be contoured in image B (Figure 4.2 dash-dot line), which will alter I With this method, increasing the threshold corresponds to better isolation of the very centre of the NBP (Figure 4.3a), and provides a means of probing and comparing different parts of the NBP. hesperia.gsfc.nasa.gov /~jma/thesis/online/node47.html   (726 words)

Against Satisficing Consequentialism   (Site not responding. Last check: 2007-10-09)   According to the absolute level view, there is a level of utility such that in all circumstances, an act must reach that level if it is to be right; any act that reaches that level is right. When a situation is and will remain below the absolute threshold, an agent’s duty is the same as under maximizing:  she must do everything to move it towards satisfactory goodness. If the state of affairs before a person acts is below the absolute threshold, and cannot be raised to that threshold, absolute-level satisficing on its own tells him to make it as good as possible, or to bring it as close as possible to absolute satisfactoriness. web.syr.edu /~wbradley/Satisficing.htm   (3992 words)

Chapter 3 Sense & Perception The absolute threshold is defined as the smallest possible strength of a stimulus that can be detected half the time. The Difference Threshold or (Just Noticeable Difference) is the minimum amount by which stimulus intensity must be changed in order to produce a noticeable variation in sensory experience. Ernst Weber (pronouned vay-ber), a 19th century experimental psychologist, observed that the size of the difference threshold appeared to be lawfully related to initial stimulus magnitude. www.delmar.edu /socsci/Faculty/Weir/chapter3.htm   (3463 words)

THE AUDITORY SYSTEM AND HEARING   (Site not responding. Last check: 2007-10-09) At the absolute auditory threshold (the minimum sound intensity that can be perceived), there is a change in air pressure of only 0.00002 dynes per square cm - a vanishingly small deviation from the resting air pressure. This means there is a 10-millionfold range of sound intensities going from the absolute auditory threshold to the pain threshold or maximum tolerable intensity. When the absolute auditory threshold is used as the reference pressure, you must specify that the dB value is expressed in terms of Sound Pressure Level, or dB (SPL). www.hss.bond.edu.au /psyc12-210/lectures/week8.htm   (3014 words)

Comparison of Continuous and Discrete Measurements of Dyspnea During Exercise in Patients With COPD and Normal Subjects ... The absolute threshold for breathlessness was taken as the X The onset (absolute threshold) of breathlessness occurred significantly threshold corresponding to the onset of breathlessness in a www.chestjournal.org /cgi/content/full/125/1/77   (3514 words)

Absolute Threshold The minimum value of a stimulus that can be detected Absolute Threshold The minimum value of a stimulus that can be detected. Threshold The point at which a stimulus, or a change in the value of a stimulus, can just be detected. Two-Point Discrimination Threshold The minimum distance between two small points that can be detected as separate stimuli when pressed against a particular region of the skin. www.abacon.com /psychsite/glossary.html   (15877 words)

Individual Differences in Sensitivity to the Odor of 4,16-Androstadien-3-one -- Lundström et al. 28 (7): 643 -- ... The absolute threshold for androstadienone was 211 µM, expressed as concentration in solution (see Figure 1). To summarize: the absolute threshold for androstadienone is Pierce, J.D., Jr, Doty, R.L. and Amoore, J.E. Analysis of position of trial sequence and type of diluent on the detection threshold for phenyl ethyl alcohol using a single staircase method. chemse.oxfordjournals.org /cgi/content/full/28/7/643   (4530 words)

CARDIOVASCULAR AND CORONARY RISK ESTIMATION IN HYPERTENSION MANAGEMENT -- Wallis et al. 88 (3): 306 -- Heart Figure 1 Absolute cardiovascular disease (CVD) risk reductions observed in selected randomised controlled trials of antihypertensive treatments plotted against the absolute CVD risk in the placebo groups. A discussion outlining how absolute benefit is predicted by absolute risk and the implications of this for antihypertensive treatment guidelines. These were the first guidelines to advocate the use of absolute risk in antihypertensive treatment decisions. heart.bmjjournals.com /cgi/content/full/88/3/306   (4263 words)

Psyshop: Dragonfly Records - Absolute Threshold (CD) Dragonfly unleashes 'Absolute Threshold', a superb collection of deep, psychedelic and essential tracks rocking dancefloors from South Africa and Brazil to Japan and Australia to Mexico and Europe and back again. Fast, uncompromising and immaculately produced 'Absolute Threshold' showcases some of the best new tracks to emerge from the reenergized and revitalized psytrance scene, dubbed Nu-wave trance, the new sound has been ripping up dancefloors around the world this summer. Attracting a whole new generation of clubbers, Nu-wave trance looks to distance itself from the 'big room' trance currently plaguing the mainstream and is already gaining a massive following on the underground. www.psyshop.com /shop/CDs/dra/dra1cd068.html   (148 words)

Absolute Threshold Narrator: The guise of control we have over our lives is only absolute as long as we never question it and allow it to govern our being. It has happened but it was subtle, you may have missed it. Try to trace your memory back to your first conscious thought because what you face now is a very similar threshold. members.cox.net /goatlord51/threshold.html   (3585 words)

Psy406 Study Questions for Psychophysics Is discrimination a relative or an absolute judgement? Using the method of constant stimuli, we have found that Jane has an absolute threshold lower than Mary’s. Visual stimuli presented so quickly that we are not consciously aware of having seen it can influence our performance on speeded cognitive tasks (e.g., being presented with NURSE to quickly for us to consciously perceive still makes us faster to decide that DOCTOR is a real word). psych.wisc.edu /braun/406/Study/PsychStudy.html   (538 words)

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