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Psychophysical Measurement of Human Oral Experience
Published in Alan R. Hirsch, Nutrition and Sensation, 2023
Derek J. Snyder, Linda M. Bartoshuk
Thresholds have been used for sensory evaluation ever since Fechner described them in his Elemente der Psychophysik (Fechner 1860/1966), one of the first published works of experimental psychology. Although thresholds present both conceptual and practical challenges (e.g., Engen 1972; Lawless and Heymann 2010), their basic definition is straightforward: The absolute or detection threshold for a stimulus is the lowest concentration at which its presence can be detected as something, whether or not its quality can be determined. The recognition threshold, which is often slightly higher than absolute threshold, is the lowest concentration at which the primary quality of a stimulus (e.g., sweet, painful) can be identified. Finally, the difference threshold is the smallest increase in suprathreshold stimulus concentration that can be detected (i.e., the “just noticeable difference” or jnd). Clinical assessments of gustatory function typically focus on the absolute threshold, while food and consumer scientists often use difference thresholds to evaluate flavor changes or off-tastes.
Taste and smell
Published in Patrick Rabbitt, The Aging Mind, 2019
Many studies of losses of taste in old age have tested sensitivity for single chemical compounds to discover both what is the weakest concentration we can detect and, above this threshold level, what are the smallest differences that we can notice: the just-noticeable differences (jnds) that are the grist of studies in sensory psychophysics. Other issues are the relative sizes of differences that we can detect when a chemical is presented on its own, in water or is masked by other flavours in a compound of other substances.
Sensory Feedback using Electrical Stimulation of the Tactile Sense
Published in Raymond V. Smith, John H. Leslie, Rehabilitation Engineering, 2018
Andrew Y.J. Szeto, Ronald R. Riso
Generally, the JND is specified as the minimum difference in the stimulus that is correctly detected on 75% of the test trials. That level of discriminability of the stimuli is actually rather poor since it implies that 25% of the messages sent are interpreted incorrectly. Using JNDs to separate message units, the average information transferred would thus be relatively low. If a more stringent criterion for the size of the JND is used, perhaps 90 or 95% discriminability, then substantial gains in information transfer might be possible in exchange for such wider spacing between messages and hence a much wider stimulus range. Unfortunately, specific experiments that focus directly on information transferred for electrocutaneous codes as a function of stimulus separation have not been reported.
The perceptual limitations of troubleshooting hearing-aids based on patients’ descriptions
Published in International Journal of Audiology, 2021
Benjamin Caswell-Midwinter, William M. Whitmer
In the abovementioned studies, participants made psychophysical same-different judgments on the objective acoustic equivalence of stimuli, and discrimination thresholds were measured. Judgments on a gain adjustment less than a discrimination threshold will be inefficient and will result in meaningless patient feedback, as the adjustment will not be perceptually distinguishable from the previous setting. However, when comparing adjustments in the clinic, patients make preference judgments on the subjective nature of stimuli. Preference judgments are more complex than psychophysical judgments given that they are subjective, and have real-world consequence. While an adjustment must be of at least 1 JND to elicit a preference for one setting over another, it is unclear whether a JND adjustment itself is sufficient to elicit a preference, and if not, what magnitude does so.
Assessing lower limb position sense in stroke using the gradient discrimination test (GradDT™) and step-height discrimination test (StepDT™): a reliability and validity study
Published in Disability and Rehabilitation, 2020
Terry Gorst, Jenny Freeman, Kielan Yarrow, Jonathan Marsden
Statistical analyses were performed using SPSS version 22.0. Data were summarized using frequencies and percentages, mean and standard deviation (SD) or median and inter-quartile range (IQR) as appropriate. Data distribution was assessed for normality using Shapiro–Wilks tests and assumed normally distributed when p > 0.05. Data presented for the GradDT™ and StepDT™ represent gradient or height discrimination thresholds respectively, expressed in the original measurement unit (degrees or centimeters). The Just Noticeable Difference (JND) between base and comparator stimuli, in the StepDT™ is expressed as a percentage (%).
Tactile-Based Pantomime Grasping: Knowledge of Results is Not Enough to Support an Absolute Calibration
Published in Journal of Motor Behavior, 2019
Matthew Heath, Jillian Chan, Shirin Davarpanah Jazi
Recent work by our group has adapted the memory-guided visual pantomime-grasping task to examine perception/action dissociations in the somatosensory domain (Davarpanah Jazi & Heath, 2014; Davarpanah Jazi, Hosang, & Heath, 2015a; see also Anema, Wolswijk, Ruis, & Dijkerman, 2008). Naturalistic tactile grasps require that a participant hold a target that fits in the palm of their non-grasping (i.e., the left) hand and reach to grasp it with their opposite (i.e., right) hand, whereas pantomime-grasps require that the target object is removed from the non-grasping hand prior to grasping onset (i.e., memory-guided). In both conditions, participants are precluded from seeing the target object or the grasping environment. As a result, the size of the target is defined – and the movement is planned – entirely on the basis of mechanical deformation of the skin (i.e., tactile feedback). Such a procedure is therefore distinct from visually based pantomime grasps in that it provides a framework for examining perception-action dissociations in somatosensory processing. Additionally, our group computed the just-noticeable-difference (JND) scores associated with naturalistic and pantomime-grasps to examine whether the conditions differentially adhered to – or violated – Weber's law (for extensive review see Marks & Algom, 1998). Weber's law asserts that the JND associated with perceiving a change between an original (e.g., target object) and a comparator (e.g., grip aperture) stimulus is in constant proportion to the magnitude of the original stimulus, and that the sensitivity of detecting a change in any physical continuum is relative and not absolute (for reviews of Weber's law in grasping see Ganel, Chajut, & Algom, 2008; Heath, Davarpanah Jazi, & Holmes, 2015). The results for PGA mirrored those reported in the visual domain, and JNDs for naturalistic and pantomime-grasps violated and adhered to Weber's law, respectively. Results were interpreted as evidence that tactile-based naturalistic grasps are supported by absolute target size information, whereas pantomime-grasps are subserved via relative target size information.