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Haptic Just Noticeable Difference in Continuous Probing of Volume Data
... Just noticeable difference (JND) is a psychophysical concept to describe the smallest difference between two stimuli that a person can reliably detect [7]. The JND differs for each sense and different types of stimuli. ...
... The JND differs for each sense and different types of stimuli. Under the psychophysics domain, there is work on examining the JND for tactile and haptics qualities; including JND in texture roughness [71], shape [75], force magnitude [2], force direction [78], friction [58], and continuous probing [7]. ...
While visual channels (e.g., color, shape, size) have been explored for visualizing data in data physicalizations, there is a lack of understanding regarding how to encode data into physical material properties (e.g., roughness, hardness). This understanding is critical for ensuring data is correctly communicated and for potentially extending the channels and bandwidth available for encoding that data. We present a method to encode ordinal data into roughness, validated through user studies. In the first study, we identified just noticeable differences in perceived roughness from this method. In the second study, we 3D-printed proof of concepts for five different multivariate physicalizations using the model. These physicalizations were qualitatively explored (N=10) to understand people’s comprehension and impressions of the roughness channel. Our findings suggest roughness may be used for certain types of data encoding, and the context of the data can impact how people interpret roughness mapping direction.
... Forskningsresultaten har presenterats i form av 3 doktorsavhandlingar (Petter Bivall, 2010;Mari Stadig Degerman, 2012;Caroline Larsson, 2013), 14 artiklar i internationella tidskrifter, 1 bokkapitel, 3 manuskript, 18 refereegranskade konferensartiklar och två populärvetenskapliga artiklar. ...
Internet-based telepresence and teleaction systems require packet-based transmission of haptic data and typically gener-ate high packet rates between operator and teleoperator. This leads to the necessity of packet rate reduction techniques. The so-called deadband approach presented earlier by the authors uses a psychophysically motivated scheme based on Weber's difference threshold (just noticable difference -JND) where force sample values are only transmitted if the change ex-ceeds this threshold. This approach has been extended to three dimensions resulting in an additional perceptual domain -namely force direction. An experimental evaluation with hu-man subjects was conducted in order to examine the change of the JND in 3D when force magnitude and force direction are combined. Our results show that the extension into dimen-sions yields to an increased JND in certain cases. Thus, higher compression ratios of haptic data and reduction in number of packets sent over the network can be reached.
Prior studies have shown that local surface orientation is a dominant source of information for haptic curvature perception in static conditions. We show that this dominance holds for dynamic touch, just as was shown earlier for static touch. Using an apparatus specifically developed for this purpose, we tested this hypothesis by providing observers with two independently controlled sources of geometric information. The robotic-like apparatus could accurately control the position of a contact surface independently from its orientation in space, while allowing subjects to freely and actively explore virtual shapes in the lateral direction. In the first experiment, we measured discrimination thresholds for the two types of shape information and compared the discrimination of real shapes to that of virtual shapes. The results confirmed the dominance of local surface orientation. We propose a model that predicts cue dominance for different scales of exploration. In the second experiment, we investigated whether a virtual curved surface felt as curved as a real curved surface. We found that observers did not systematically judge either of the two kinds of stimuli to be more curved than the other. More importantly, we found that points of subjective curvedness were not influenced by the availability of height information.
This paper describes the use of a magnetic levitation haptic device (MLHD) to study the psychophysics of tex- ture roughness. Studies of texture roughness perception per- formed using real textures can be time consuming and ex- pensive. By using a MLHD to simulate texture we are able to quickly and easily adjust texture parameters. A dithered textured surface composed of conical elements is simulated using a constraint surface algorithm. The constraint sur- face shape is defined by the geometry of the elements as well as the size and shape of the virtual probe. The spac- ing of the elements and the size of the probe can be varied continuously and in real time. Just noticeable difference (JND) experiments were con- ducted over the parameters of probe radius and texture spacing. The JND of roughness was determined with re- spect to element spacing using unforced weighted up-down adaptive threshold estimation. JND's were found to vary for texture spacing and probe size. JND's for constant probe size decreased with increasing texture spacing to a mini- mum and then increased again. JND's for constant spacing increased as probe size increased. These results are con- sistent with a geometric model of probe-texture interaction.
Most studies on the haptic perception of force direction have been conducted without hand movements, whereas hand movements
are normally required in real-world applications. This paper reports a study on the perception of haptic force direction during
hand movement. Discrimination thresholds for force direction were determined for two hand movement speeds, slow and fast,
and for five reference force directions. The results show that the perception of force direction is not affected by hand movement
speed. We also found that the perception of force direction was not impaired by the hand motion, nor by the direction of the
reference force.
During the past decade a number of variations in the simple up‐down procedure have been used in psychoacoustic testing. A broad class of these methods is described with due emphasis on the related problems of parameter estimation and the efficient placing of observations. The advantages of up‐down methods are many, including simplicity, high efficiency, robustness, small‐sample reliability, and relative freedom from restrictive assumptions. Several applications of these procedures in psychoacoustics are described, including examples where conventional techniques are inapplicable.
Describes preliminary work in the use of a virtual environment to
derive just noticeable differences (JNDs) for force. Specifically, we
look for thresholds of force sensitivity so that we may ultimately
construct therapeutic force feedback distortions that stay below these
thresholds. Initially, we have concentrated on JNDs as they are applied
to the index finger; preliminary data in healthy individuals shows an
average JND of approximately 100%. More significantly, the data indicate
that visual feedback distortions in a virtual environment can be created
to encourage increased force productions by up to 100%, and that this
can be done without a patient's awareness
This paper presents a quantitative study of the effects of maximum capable force magnitude of a haptic interface on the haptic perception of detail. Specifically, the haptic perception of detail is characterized by identification, detection, and discrimination of round and square cross-section ridges, in addition to corner detection tests. Test results indicate that performance, measured as a percent correct score in the perception experiments, improves in a nonlinear fashion as the maximum allowable level of force in the simulation increases. Further, all test subjects appeared to reach a limit in their perception capabilities at maximum-force output levels of 3-4 N, while the hardware was capable of 10 N of maximum continuous force output. These results indicate that haptic interface hardware may be able to convey sufficient perceptual information to the user with relatively low levels of force feedback. The data is compiled to aid those who wish to design a stylus-type haptic interface to meet certain requirements for the display of physical detail within a haptic simulation.
This paper describes preliminary work in the use of a virtual environment to derive just noticeable differences (JNDs) for force. Specifically, we look for thresholds of force sensitivity so that we may ultimately construct therapeutic force feedback distortions that stay below these thresholds. Initially, we have concentrated on JNDs as they are applied to the index finger; preliminary data in healthy individuals shows an average JND of approximately 10%. More significantly, the data indicate that visual feedback distortions in a virtual environment can be created to encourage increased force productions by up to 10%, and that this can be done without a patient's awareness. 1.
Discriminability along the dimension of meaningfulness, as defined by Noble's m′ scale, was studied in two experiments. In a pilot experiment, an attempt to establish the just noticeable difference (j.n.d.) at two portions of the scale (high and medium) was unsuccessful since the j.n.d. apparently exceeded the range of scale values used (1/6 of the scale). Therefore, the first experiment made use of a much larger portion of the scale (2/3) and a single j.n.d. was calculated at .96, a value representing 1/5 of the entire scale. The Ss in the second study were run individually as opposed to the group situation of the first. The difference threshold in the second experiment was smaller, about 1/7 of the whole scale. Reasons for the differences among the pilot study and the two experiments were discussed, and suggestions made about the use of m′ as an independent variable, in light of the large j.n.d.
ABSTRACT The authors report an experiment,in which,twenty-five partici- pants discriminated force vectors presented along five directions (up, left, right, diagonally up left, diagonally up right). The force vectors were presented with a three ,degree-of-freedom force- feedback device. A three-interval one-up three-down adaptive procedure was used. The five reference force-direction condi- tions were presented in randomly,interleaved order. The results show an average force-direction discriminationthreshold of 33° regardless of the ,reference-force direction. Position data recorded at a nominal sampling rate of 200 Hz revealed a 10.1 mm average displacement of the fingertip between the start and end positions in a trial. The average maximum,deviation from the starting position within a trial was 21.3 mm. We conclude that the resolution with which ,people can discriminate force direction is not dependent,on the,direction of the force per se. These results are useful for designers of haptic virtual environ- ments.
This study explores the haptic rendering capabilities of a variable friction tactile interface through psychophysical experiments. In order to obtain a deeper understanding of the sensory resolution associated with the Tactile Pattern Display (TPaD), friction discrimination experiments are conducted. During the experiments, subjects are asked to explore the glass surface of the TPaD using their bare index fingers, to feel the friction on the surface, and to compare the slipperiness of two stimuli, displayed in sequential order. The fingertip position data is collected by an infrared frame and normal and translational forces applied by the finger are measured by force sensors attached to the TPaD. The recorded data is used to calculate the coefficient of friction between the fingertip and the TPaD. The experiments determine the just noticeable difference (JND) of friction coefficient for humans interacting with the TPaD.
Haptic interfaces are used increasingly in medical systems and related applications, but relatively little is known on the effectiveness of these interfaces. This paper reports a study on the perception of haptic force magnitude during hand movements. Discrimination thresholds were determined for a reference force of 1.5N in five different directions (0deg, 45deg, 90deg, 135deg, and 180deg) with respect to the movement direction. We found that force discrimination thresholds detected were significantly higher during hand movement than those reported previously without hand movement, indicating that the perception of force magnitude is impaired by hand movement. The results also show there is no significant difference between the discrimination thresholds found for fast (28 mm/s) and slow (14 mm/s) hand movements. Finally, we found that the perception of force magnitude is impaired at a force direction of 45deg with respect to the hand movement, indicating the existence of an oblique effect.
Data-driven haptic rendering requires processing of raw recorded signals, which leads to high computational effort for large datasets. To achieve real-time performance, one possibility is to reduce the parameter space of the employed interpolation technique, which generally decreases the accuracy in the rendering. In this paper, we propose a method for guiding this parameter reduction to maintain high accuracy with respect to the just noticeable difference for forces. To this end, we performed a user study to estimate this perception threshold. The threshold is used to assess the final error in the rendered forces as well as for the parameter reduction process. Comparison with measured data from real object interactions confirms the accuracy of our method and highlights the reduced computational effort.
Multimodality is considered a promising approach for universal access, and haptic interaction has the potential to constitute an added dimension to multimodal interfaces. This paper describes the influence of colors on the haptic perception of textured surfaces, based on 8 experiments. Our results show that (1) colors do have an influence on haptic perception, but they do not make the perception error rate higher than when no color is used; (2) up to 6 different types of colors can be used in haptic interfaces without worsening the haptic perception; (3) yellow has an error rate that is statistically significantly lower than that of 3 other color conditions, and can be used without worsening the haptic perception; (4) our finding of two special orders for haptic perception demonstrates that human haptic perception is very sensitive to continuously increasing or decreasing changes of roughness, but has difficulty discerning randomly changed roughness.
The ability of technology to transmit multi-media is very dependent on compression techniques. In particular lossy compression
has been used in image compression (jpeg) audio compression (mp3) and video compression (mpg) to allow the transmission of
audio and video over broadband network connections. Recently the sense of touch or haptics is becoming more important with
its addition in computer games or in cruder applications such as vibrations in a cell phone. As haptic technology improves
the ability to transmit compressed force sensations becomes more critical. Most lossy audio and visual compression techniques
rely on the lack of sensitivity in humans to pick up detailed information in certain scenarios. Similarly limitations in the
sensitivity of human touch could be exploited to create haptic models with much less detail and thus requiring smaller bandwidth.
The focus of this paper is on the force thresholds of the human haptic system that can be used in a psychophysically motivated
lossy haptic (force) compression technique. Most of the research in this field has measured the just noticeable difference
(JND) of the human haptic system with a human user in static interaction with a stationary rigid object. In this paper our
focus involves cases where the human user or the object are in relative motion. An example of such an application would be
the haptic rendering of the user’s hand in contact with of a high-viscous material or interacting with a highly deformable
object. Thus an approach is presented to measure the force threshold based on the velocity of the user’s hand motion. Two
experiments are conducted to detect the absolute force threshold (AFT) of the human haptic system using methodologies from
the field of psychophysics. The AFTs are detected for three different ranges of velocity of the user’s hand motion. This study
implies that when a user’s hand is in motion fewer haptic details are required to be stored calculated or transmitted. Finally
the implications of this study on a more complete future study will be discussed.
Differential thresholds for limb movement were measured in 10 subjects, using the transformed up-down procedure. Subjects were required to indicate which of two random displacement perturbations delivered to their forearms had the larger standard deviation (SD). The SD of the reference signal was fixed for each experimental condition at one of seven values ranging from 0.05 to 3.2 mm. THe SD of the other signal varied depending on the subject's response. Using this procedure, the differential threshold for limb movement was calculated to be 8%, which is very similar to the thresholds estimated previously for changes in limb position (9%) and force (7%). The sensitivity of the human proprioceptive system to changes in limb displacement was much greater than anticipated, with subjects being able to resolve a 5-microns difference between two perturbations delivered to their arms.
As research on sensation and perception has grown more sophisticated during the last century, new adaptive methodologies have been developed to increase efficiency and reliability of measurement. An experimental procedure is said to be adaptive if the physical characteristics of the stimuli on each trial are determined by the stimuli and responses that occurred in the previous trial or sequence of trials. In this paper, the general development of adaptive procedures is described, and three commonly used methods are reviewed. Typically, a threshold value is measured using these methods, and, in some cases, other characteristics of the psychometric function underlying perceptual performance, such as slope, may be developed. Results of simulations and experiments with human subjects are reviewed to evaluate the utility of these adaptive procedures and the special circumstances under which one might be superior to another.
We are interested in using a virtual environment with a robotic device to extend the strength and mobility of people recovering from strokes by steering them beyond what they had thought they were capable of doing. Previously, we identified just noticeable differences (JND) of a finger's force production and position displacement in a virtual environment. In this paper, we extend this investigation by identifying peoples' tolerance for distortions of visual representations of force production and positional displacement in a virtual environment. We determined that subjects are not capable of reliably detecting inaccuracies in visual representation until there is 36% distortion. This discrepancy between actual and perceived movements is significantly larger than the JNDs reported in the past, indicating that a virtual robotic environment could be a valuable tool for steering actual movements further away from perceived movements. We believe this distorted condition may allow people recovering from strokes, even those who have perceptual or cognitive deficits, to rehabilitate with greater ease.
NOTES AND DISCUSSIONS THE STAIRCASE-METHOD IN PSYCHOPHYSICS A psychophysical method variously referred to as the method of up and downs, 1 the Bekesy audiometric method, 2 or the staircase-method, has come into extensive use in the last few years. The method has several advantages over other more commonly used techniques but it also has some disadvantages. This paper will illustrate the use of the method, will discuss its relative merits and demerits, and will describe a modification which overcomes certain of the disadvantages of the method. The staircase-method is best described by illustrating its use with a specific prob- lem. Suppose the problem is to determine S's absolute, intensive threshold for the sound of a click. The first stimulus that E delivers is a click of some arbitrary intensity. S responds either that he did or did not hear it. If S says 'yes' (he did hear it), the next stimulus is made less intense, and if S says 'no,' the second stimulus is made more intense. If S responds 'yes' to the second stimulus, the third is made less intense, and if he says 'no,' it is made more intense. This procedure is simply continued until some predetermined criterion or 'number of trials' is reached. The results of a series of 30 trials are shown in Fig. 1. The results may be recorded directly on graph-paper; doing so helps E keep the procedure straight. There are a number of ways of determining the intensive value that represents the threshold. The simplest is to compute the mean of the values of a given num- ber of stimuli delivered after the series has reached its final level. This requires an arbitrary decision about when the final level has been reached. The technique, which avoids this difficulty and yields a 50% value, is simply to determine the stimulus above which 50% of the responses are 'yes,'-i.e. in Fig. 1 between 61 and 62 db. Statistical treatment of the results has been discussed by Dixon and Massey, who describe the techniques for determining the means, standard deviations, standard errors, etc., for this type of data.3 The treatments assume, however, that the response to each stimulus is independent of the preceding stimuli and pre- ceding responses. This assumption holds for the examples analyzed, but there is evidence that the assumption does not always hold for human Ss in psychophysical experiments.• The development of techn.iques that take the existing inter-actions into account has not as yet been achieved. W. J. Dixon and F. J. Massey, lnt,.oduction lo Statistical Analysis, 1957, 279· •Georg von Bekesy, A new audiometer, A'la 010-/a,.yngol., 35, 1947, 411-422. •Dixon and Massey, op. cit., 286. • W. S. Verplanck, G. H. Collier, and J. W. Cotton, Nonindependence of succes- sive responses in measurement of the visual threshold, /. exp. Psycho/., 42, 1952, 273-282; Verplanck and Cotton, The dependence of frequencies of seeing on pro- cedural variables: J. Direction and length of series of intensity-ordered stimuli, /. gen. Psycho/., 53, 1955, 37-47; V. L. Senders, Further analysis of response se- quences in the setting of a psychophysical experiment, this JOURNAL, 66, 1 953, 215-229; R. S. Woodworth and Harold Schlosberg, Experimental Psychology, 1954,
The M-AFC (alternatively forced choice) transformed up-down
adaptive method for the rapid determination of visual thresholds in
medical images is described. The method is very efficient in obtaining
thresholds to medical imaging parameters; in addition, it is free from
criterion bias, an important concern in radiology, and it is free from
parametric assumptions about the stimulus scale, which is often unknown
due to the complexity of medical images. Issues of experimental design
are presented that arise in the use of this method, and the
psychological caveats which should be followed with human observers are
noted. Two experiments are presented to demonstrate the method's
efficacy in determining thresholds and psychometric functions in medical
images
Evaluation of directional force threshold through psychophysics experiments
- Marco Vicentini
- Maria Carla De Maggio
- Debora Botturi
- Paolo Fiorini
Marco Vicentini, Maria Carla De Maggio, Debora Botturi, and Paolo Fiorini. Evaluation of directional force threshold through psychophysics experiments. In A. Luciani and C. Cadoz, editors, Proceedings of the 4th International Conference on Enactive Interfaces 2007, pages 297-300, Grenoble,
France, November 2007.