Astrid M L Kappers

VU University Amsterdam, Amsterdamo, North Holland, Netherlands

Are you Astrid M L Kappers?

Claim your profile

Publications (278)368.69 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In a haptic search task, one has to determine the presence of a target among distractors. It has been shown that if the target differs from the distractors in two properties, shape and texture, performance is better than in both single-property conditions (Van Polanen, Bergmann Tiest, & Kappers, 2013). The search for a smooth sphere among rough cubical distractors was faster than both the searches for a rough sphere (shape information only) and for a smooth cube (texture information only). This effect was replicated in this study as a baseline. The main focus here was to further investigate the nature of this integration. It was shown that performance is better when the two properties are combined in a single target (smooth sphere), than when located in two separate targets (rough sphere and smooth cube) that are simultaneously present. A race model that assumes independent parallel processing of the two properties could explain the enhanced performance with two properties, but this could only take place effectively when the two properties were located in a single target.
    Acta psychologica 05/2014; 150C:35-40. · 2.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: From previous studies, it is unclear how bimanual length discrimination differs from unimanual length discrimination. To investigate the difference, we designed an experiment with four conditions. In the first two conditions, unimanual and bimanual discrimination thresholds are determined. In the third and fourth conditions, length is explored with the two index fingers like in the bimanual condition, but the reference is either internal, by clasping the hands together, or external, by grasping handles connected to the table. We find that thresholds for the unimanual condition (7.0 %) and the clasping condition (9.2 %) are both lower than for the bimanual condition (16 %) and the grasping handles condition (15 %). We conclude that when discriminating length unimanually and bimanually while clasping the hands together, the internal reference within the hand can be used and that explains the lower discrimination thresholds.
    Experimental Brain Research 05/2014; · 2.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigated if and how length and curvature information are integrated when an object is explored in one hand. Subjects were asked to explore four types of objects between thumb and index finger. Objects differed in either length, curvature, both length and curvature correlated as in a circle, or anti-correlated. We found that when both length and curvature are present, performance is significantly better than when only one of the two cues is available. Therefore, we conclude that there is integration of length and curvature. Moreover, if the two cues are correlated in a circular cross-section instead of in an anti-correlated way, performance is better than predicted by a combination of two independent cues. We conclude that integration of curvature and length is highly efficient when the cues in the object are combined as in a circle, which is the most common combination of curvature and length in daily life.
    Scientific Reports 01/2014; 4:3856. · 5.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In a haptic search task, one has to determine the presence of a target among distractors. It has been shown that if the target differs from the distractors in two properties, shape and texture, performance is better than in both single-property conditions (Van Polanen, Bergmann Tiest, & Kappers, 2013). The search for a smooth sphere among rough cubical distractors was faster than both the searches for a rough sphere (shape information only) and for a smooth cube (texture information only). This effect was replicated in this study as a baseline. The main focus here was to further investigate the nature of this integration. It was shown that performance is better when the two properties are combined in a single target (smooth sphere), than when located in two separate targets (rough sphere and smooth cube) that are simultaneously present. A race model that assumes independent parallel processing of the two properties could explain the enhanced performance with two properties, but this could only take place effectively when the two properties were located in a single target.
    Acta Psychologica. 01/2014; 150:35–40.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: While quite some research has focussed on the accuracy of haptic perception of distance, information on the precision of haptic perception of distance is still scarce, particularly regarding distances perceived by making arm movements. In this study, eight conditions were measured to answer four main questions, which are: what is the influence of reference distance, movement axis, perceptual mode (active or passive) and stimulus type on the precision of this kind of distance perception? A discrimination experiment was performed with twelve participants. The participants were presented with two distances, using either a haptic device or a real stimulus. Participants compared the distances by moving their hand from a start to an end position. They were then asked to judge which of the distances was the longer, from which the discrimination threshold was determined for each participant and condition. The precision was influenced by reference distance. No effect of movement axis was found. The precision was higher for active than for passive movements and it was a bit lower for real stimuli than for rendered stimuli, but it was not affected by adding cutaneous information. Overall, the Weber fraction for the active perception of a distance of 25 or 35 cm was about 11% for all cardinal axes. The recorded position data suggest that participants, in order to be able to judge which distance was the longer, tried to produce similar speed profiles in both movements. This knowledge could be useful in the design of haptic devices.
    PLoS ONE 01/2014; 9(8):e104769. · 3.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Haptic perception is bidirectionally related to exploratory movements, which means that exploration influences perception, but perception also influences exploration. We can optimize or change exploratory movements according to the perception and/or the task, consciously or unconsciously. This paper presents a psychophysical experiment on active roughness perception to investigate movement changes as the haptic task changes. Exerted normal force and scanning velocity are measured in different perceptual tasks (discrimination or identification) using rough and smooth stimuli. The results show that humans use a greater variation in contact force for the smooth stimuli than for the rough stimuli. Moreover, they use higher scanning velocities and shorter break times between stimuli in the discrimination task than in the identification task. Thus, in roughness perception humans spontaneously use different strategies that seem effective for the perceptual task and the stimuli. A control task, in which the participants just explore the stimuli without any perceptual objective, shows that humans use a smaller contact force and a lower scanning velocity for the rough stimuli than for the smooth stimuli. Possibly, these strategies are related to aversiveness while exploring stimuli.
    PLoS ONE 01/2014; 9(3):e93363. · 3.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In a haptic search task, one has to detect the presence of a target among distractors using the sense of touch. A salient target can be detected faster than a non-salient target. However, little is known about the exploration strategies that are used, especially in 3D search tasks where items are held in the hand. In this study, we investigated which parts of the hand were used to contact the target and which strategies were performed. Blindfolded participants performed search tasks in four conditions, where the targets differed in relevant property and saliency. The positions of the target and the hand were tracked during exploration. It was found that target saliency had a large effect on the use of the hand parts and the strategies. In the non-salient target conditions, the fingers, especially the thumb, contacted the target more often than in the salient target conditions. This could also be seen in the strategies, where the thumb was used to explore the items in a serial way by moving them in the hand or touching them individually. In the salient target conditions, more parallel strategies like grasping or shuffling of the items in the hand were used.
    Scientific reports. 01/2014; 4:6254.
  • Astrid M L Kappers, Wouter M Bergmann Tiest
    [Show abstract] [Hide abstract]
    ABSTRACT: RECENTLY, WE SHOWED A STRONG HAPTIC SIZE AFTEREFFECT BY MEANS OF A SIZE BISECTION TASK: after adaptation to a large sphere, subsequently grasped smaller test spheres felt even smaller, and vice versa. In the current study, we questioned whether the strength of this aftereffect depends on shape. In four experimental conditions, we determined the aftereffect after adaptation to spheres and tetrahedra and subsequent testing also with spheres and tetrahedra. The results showed a clear influence of shape: the haptic aftereffect was much stronger if adaptation and test stimuli were identical in shape than if their shapes were different. Therefore, it would be more appropriate to term such aftereffects haptic shape-size aftereffects, as size alone could not be the determining factor. This influence of shape suggests that higher cortical areas are involved in this aftereffect and that it cannot be due to adaptation of peripheral receptors. An additional finding is that the geometric property or combination of properties participants use in the haptic size bisection task varies widely over participants, although participants themselves are quite consistent.
    PLoS ONE 01/2014; 9(2):e88729. · 3.73 Impact Factor
  • Astrid M L Kappers, Wouter M Bergmann Tiest
    [Show abstract] [Hide abstract]
    ABSTRACT: Haptic matching of the orientation of bars separated by a horizontal distance leads to large systematic deviations. This finding leads to the following intriguing question which we investigated in this study: How will a bar moving from left to right in a fixed orientation be perceived by blindfolded observers? Interestingly, this previous finding predicts that the translating bar will cause the illusory perception of a rotation. In our experiment, we used psychophysical methods to determine the rotation needed to perceive the bar as non-rotating, for both rightward and leftward translations. From our results, it can be estimated that, on average, a bar translating in parallel over 60 cm is perceived as rotating 18°, so we established that the predicted illusory rotation indeed exists. This implies that static and dynamic signals are processed in a similar way.
    Experimental Brain Research 09/2013; · 2.22 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Active movement of the hand and fingers enables dynamic exploration of objects. Lederman and Klatzky [1987] have proposed a set of stereotyped movement patterns called Exploratory Procedures (EPs) that are linked to the acquisition of knowledge concerning specific object properties. For example, lateral motion is the optimal EP for acquiring roughness information and compliance is best estimated by employing pressure.
    Proceedings of the ACM Symposium on Applied Perception; 08/2013
  • Rick van Dijk, Astrid M L Kappers, Albert Postma
    [Show abstract] [Hide abstract]
    ABSTRACT: The present study investigated haptic spatial orientation processing in deaf signers, hearing sign language interpreters, and hearing controls. Blindfolded participants had to set two bars parallel in the horizontal plane, with either a 2-s or a 10-s delay between inspection of the reference bar and the setting of the test bar. The deaf group outperformed the other two groups which did not differ from each other. Together these results indicate that deaf individuals can better identify the allocentric spatial coordinates of haptically inspected orientations. These results are discussed in terms of the possible neurocognitive consequences of auditory deprivation.
    Experimental Brain Research 07/2013; · 2.22 Impact Factor
  • Astrid M.L. Kappers, Wouter M. Bergmann Tiest
    [Show abstract] [Hide abstract]
    ABSTRACT: Fueled by novel applications, interest in haptic perception is growing. This paper provides an overview of the state of the art of a number of important aspects of haptic perception. By means of touch we can not only perceive quite different material properties, such as roughness, compliance, friction, coldness and slipperiness, but we can also perceive spatial properties, such as shape, curvature, size and orientation. Moreover, the number of objects we have in our hand can be determined, either by counting or subitizing. All these aspects will be presented and discussed in this paper. Although our intuition tells us that touch provides us with veridical information about our environment, the existence of prominent haptic illusions will show otherwise. Knowledge about haptic perception is interesting from a fundamental viewpoint, but it also is of eminent importance in the technological development of haptic devices. At the end of this paper, a few recent applications will be presented. WIREs Cogn Sci 2013, 4:357–374. DOI: 10.1002/wcs.1238 Conflict of interest: The authors have declared no conflicts of interest for this article. For further resources related to this article, please visit the WIREs website.
    Wiley interdisciplinary reviews. Cognitive science 07/2013; 4(4). · 0.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The study examined exploratory procedures (EPs) of congenitally blind and sighted children and adults on a haptic match-to-sample task. The aim was to examine the influence of age, visual status, and familiarity on the use of EPs when people haptically examine the object properties of weight, size, exact shape, and texture. EPs in the first and last of four series of trials were compared. The results showed that all four groups chose the same dominant EP for examining the four different object properties, all of them in agreement with the ones found by Lederman and Klatzky (Cognitive Psychology 19:342-368, 1987). Children were found to use more EPs, rather than using only the most efficient EP, for the dimension under study. Overall, performance was affected more by age than by visual status, and repeating the task led to increased efficiency in all groups. To describe exploratory behaviors in more detail, actions were introduced. Actions are single or sequential hand movements occurring in parallel with the EPs or apart from the EPs. The use of actions explained, in part, individual variation among the participants.
    Attention Perception & Psychophysics 06/2013; · 1.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: OBJECTIVE: To investigate the relative frequency of the genetic causes of the Schubert-Bornschein type of congenital stationary night blindness (CSNB) and to determine the genotype-phenotype correlations in CSNB1 and CSNB2. DESIGN: Clinic-based, longitudinal, multicenter study. PARTICIPANTS: A total of 39 patients with CSNB1 from 29 families and 62 patients with CSNB2 from 43 families. METHODS: Patients underwent full ophthalmologic and electrophysiologic examinations. On the basis of standard electroretinograms (ERGs), patients were diagnosed with CSNB1 or CSNB2. Molecular analysis was performed by direct Sanger sequencing of the entire coding regions in NYX, TRPM1, GRM6, and GPR179 in patients with CSNB1 and CACNA1F and CABP4 in patients with CSNB2. MAIN OUTCOME MEASURES: Data included genetic cause of CSNB, refractive error, visual acuity, nystagmus, strabismus, night blindness, photophobia, color vision, dark adaptation (DA) curve, and standard ERGs. RESULTS: A diagnosis of CSNB1 or CSNB2 was based on standard ERGs. The photopic ERG was the most specific criterion to distinguish between CSNB1 and CSNB2 because it showed a "square-wave" appearance in CSNB1 and a decreased b-wave in CSNB2. Mutations causing CSNB1 were found in NYX (20 patients, 13 families), TRPM1 (10 patients, 9 families), GRM6 (4 patients, 3 families), and GPR179 (2 patients, 1 family). Congenital stationary night blindness 2 was primarily caused by mutations in CACNA1F (55 patients, 37 families). Only 3 patients had causative mutations in CABP4 (2 families). Patients with CSNB1 mainly had rod-related problems, and patients with CSNB2 had rod- and cone-related problems. The visual acuity on average was better in CSNB1 (0.30 logarithm of the minimum angle of resolution [logMAR]) than in CSNB2 (0.52 logMAR). All patients with CSNB1 and only 54% of the patients with CSNB2 reported night blindness. The dark-adapted threshold was on average more elevated in CSNB1 (3.0 log) than in CSNB2 (1.8 log). The 3 patients with CABP4 had a relative low visual acuity, were hyperopic, had severe nonspecific color vision defects, and had only 1.0 log elevated DA threshold. CONCLUSIONS: Congenital stationary night blindness 1, despite different causative mutations, shows 1 unique CSNB1 phenotype. Congenital stationary night blindness 2 caused by mutations in CABP4 merely shows cone-related problems and therefore appears to be distinct from CSNB2 caused by mutations in CACNA1F. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
    Ophthalmology 05/2013; · 5.56 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: There is evidence that blind people may strengthen their memory skills to compensate for absence of vision. However, which aspects of memory are involved is open to debate and a developmental perspective is generally lacking. In the present study, we compared the short term memory (STM) and working memory (WM) of 10-year-old blind children and sighted children. STM was measured using digit span forward, name learning, and word span tasks; WM was measured using listening span and digit span backward tasks. The blind children outperformed their sighted peers on both STM and WM tasks. The enhanced capacity of the blind children on digit span and other STM tasks confirms the results of earlier research; the significantly better performance of the blind children relative to their sighted peers on verbal WM tasks is a new interesting finding. Task characteristics, including the verbal nature of the WM tasks and strategies used to perform these tasks, are discussed.
    Research in developmental disabilities 04/2013; 34(7):2161-2172. · 4.41 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Advanced flexible endoscopes and instruments with multiple degrees of freedom enable physicians to perform challenging procedures such as the removal of large sections of mucosal tissue. However, these advanced endoscopes are difficult to control and require several physicians to cooperate. METHODS: In this article, we present a robotic system that allows the physician to control an instrument in an intuitive way, using a haptic device. Performance with the robotic and conventional control methods were compared in a human subjects experiment. Subjects used both methods to tap a series of targets. They performed four trials while looking at the endoscopic monitor, and two trials while looking at the instrument directly. RESULTS: Subjects were significantly faster using the robotic method, 54 s vs 164 s. Their performance in the second trial was significantly improved with respect to the first trial. CONCLUSIONS: This study provides evidence that the robotic control method can be implemented to improve the performance of physicians using advanced flexible endoscopes. Copyright © 2013 John Wiley & Sons, Ltd.
    International Journal of Medical Robotics and Computer Assisted Surgery 04/2013; · 1.49 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In a search task, where one has to search for the presence of a target among distractors, the target is sometimes easily found, whereas in other searches it is much harder to find. The performance in a search task is influenced by the identity of the target, the identity of the distractors and the differences between the two. In this study, these factors were manipulated by varying the target and distractors in shape (cube or sphere) and roughness (rough or smooth) in a haptic search task. Participants had to grasp a bundle of items and determine as fast as possible whether a predefined target was present or not. It was found that roughness and edges were relatively salient features and the search for the presence of these features was faster than for their absence. If the task was easy, the addition of these features could also disrupt performance, even if they were irrelevant for the search task. Another important finding was that the search for a target that differed in two properties from the distractors was faster than a task with only a single property difference, although this was only found if the two target properties were non-salient. This means that shape and texture can be effectively integrated. Finally, it was found that edges are more beneficial to a search task than disrupting, whereas for roughness this was the other way round.
    PLoS ONE 01/2013; 8(7):e70255. · 3.73 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Two experiments evaluated the ability of 30 older and younger adults to discriminate the curvature of simple object surfaces from static and dynamic touch. The ages of the older adults ranged from 66 to 85 years, while those of the younger adults ranged from 20 to 29 years. For each participant in both experiments, the minimum curvature magnitude needed to reliably discriminate between convex and concave surfaces was determined. In Experiment 1, participants used static touch to make their judgments of curvature, while dynamic touch was used in Experiment 2. When static touch was used to discriminate curvature, a large effect of age occurred (the thresholds were 0.67 & 1.11/m for the younger and older participants, respectively). However, when participants used dynamic touch, there was no significant difference between the ability of younger and older participants to discriminate curvature (the thresholds were 0.58 & 0.59/m for the younger and older participants, respectively). The results of the current study demonstrate that while older adults can accurately discriminate surface curvature from dynamic touch, they possess significant impairments for static touch.
    PLoS ONE 01/2013; 8(7):e68577. · 3.73 Impact Factor
  • V. Panday, W.M.B. Tiest, A.M.L. Kappers
    [Show abstract] [Hide abstract]
    ABSTRACT: For small stimuli, it has been shown that subjects are very accurate in distinguishing a cylinder with an elliptical cross section from one with a circular cross section. In such a task, both curvature and length are integrated effectively. Large cylinders are explored differently: either by one hand or by two hands sliding over the surface. However, the same cues are available. We investigated the integration of position and curvature in unimanual and bimanual explorations. In Experiment 1, curved surfaces were presented as part of a horizontal cylinder with a cross section that was either a horizontally or a vertically elongated ellipse. We found that discrimination thresholds for unimanual exploration were significantly larger than for bimanual exploration. In Experiment 2, we found that position discrimination thresholds were independent of the type of exploration (unimanual or bimanual) and surprisingly also independent of the reference length. In Experiment 3, we found that discrimination thresholds for the position of the midsagittal plane were on an average lower than the position discrimination thresholds found in Experiment 2. From these findings, we conclude that the lower thresholds in Experiment 1 for bimanual exploration compared to unimanual exploration are due to the integration of curvature, not position or uncertainty of the midsagittal plane in unimanual exploration.
    IEEE Transactions on Haptics 01/2013; 6(3):285-295. · 1.39 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Haptic exploratory procedures (EPs) are prototypical hand movements that are linked to the acquisition of specific object properties. In studies of haptic perception, hand movements are often classified into these EPs. Here, we aim to investigate several EPs in a quantitative manner to understand how hand dynamics and contact forces differ between them. These dissimilarities are then used to construct an EP identification model capable of discriminating between EPs based on the index finger position and contact force. The extent to which the instructed EPs were distinct, repeatable, and similar across subjects was confirmed by showing that more than 95 percent of the analyzed trials were classified correctly. Finally, the method is employed to investigate haptic exploratory behavior during similarity judgments based on several object properties. It seems that discrimination based on material properties (hardness, roughness, and temperature) yields more consistent classification results compared to discrimination based on the acquisition of shape information.
    IEEE Transactions on Haptics 01/2013; 6(4):464-472. · 1.39 Impact Factor

Publication Stats

2k Citations
368.69 Total Impact Points

Institutions

  • 2013–2014
    • VU University Amsterdam
      • Faculty of Human Movement Sciences
      Amsterdamo, North Holland, Netherlands
    • Hogeschool Arnhem and Nijmegen
      Arnheim, Gelderland, Netherlands
  • 2012–2013
    • Royal Dutch Visio Centre of Expertise for Blind and Partially Sighted People
      Amsterdamo, North Holland, Netherlands
  • 1992–2013
    • Universiteit Utrecht
      • • Division of Experimental Psychology
      • • Helmholtz Institute
      • • Department of Physics of Man
      Utrecht, Provincie Utrecht, Netherlands
  • 2010
    • University of Münster
      Muenster, North Rhine-Westphalia, Germany
    • Western Kentucky University
      • Department of Psychology
      Bowling Green, KY, United States
  • 2000–2009
    • Delft University Of Technology
      • Faculty of Industrial Design Engineering
      Delft, South Holland, Netherlands
  • 1996–2007
    • The Ohio State University
      • Department of Psychology
      Columbus, OH, United States
  • 2003
    • Skidmore College
      • Department of Psychology
      Saratoga Springs, NY, United States
  • 2001
    • Technische Universiteit Eindhoven
      Eindhoven, North Brabant, Netherlands
  • 1992–1994
    • Netherlands Institute for Space Research, Utrecht
      Utrecht, Utrecht, Netherlands