Edouard Gentaz | Université de Genève (original) (raw)

Papers by Edouard Gentaz

PLoS ONE, 2008

and ellipses in Experiment 2. We observed that the use of HGF globally improves the fluency of th... more and ellipses in Experiment 2. We observed that the use of HGF globally improves the fluency of the visuo-manual tracking of trajectories while no significant improvement was found for HGP or NHG.

2010 Annual International Conference of the IEEE Engineering in Medicine and Biology, 2010

Most conventional computer-aided navigation systems assist the surgeon visually by tracking the p... more Most conventional computer-aided navigation systems assist the surgeon visually by tracking the position of an ancillary and by superposing this position into the 3D preoperative imaging exam. This paper aims at adding to such navigation systems a device that will guide the surgeon towards the target, following a complex preplanned ancillary trajectory. We propose to use tactile stimuli for such guidance, with the design of a vibrating belt. An experiment using a virtual surgery simulator in the case of skull base surgery is conducted with 9 naïve subjects, assessing the vibrotactile guidance effectiveness for complex trajectories. Comparisons between a visual guidance and a visual+tactile guidance are encouraging, supporting the relevance of such tactile guidance paradigm.

This paper examines the effect of adding haptic force cues (simulated inertia, compensation of gr... more This paper examines the effect of adding haptic force cues (simulated inertia, compensation of gravity) during 3D-path following in large immersive virtual reality environments. Thirty-four participants were asked to follow a 3D ring-on-wire trajectory. The experiment consisted of one pre-test/control bloc of twelve trials with no haptic feedback; followed by three randomized blocs of twelve trials, where force feedbacks differed. Two levels of inertia were proposed and one level compensating the effect of gravity (No-gravity). In all blocks, participants received a real time visual warning feedback (color change), related to their spatial performance. Contrariwise to several psychophysics studies, haptic force cues did not significantly change the task performance in terms of time completion or spatial distance error. The participants however significantly reduced the time passed in the visual warning zone in the presence of haptic cues. Taken together, these results are discussed from a psychophysics and multi-sensory integration point of view.

Lecture Notes in Computer Science, 2010

We studied the influence of visual feedback on the tactual perception of both speed and spatial p... more We studied the influence of visual feedback on the tactual perception of both speed and spatial period of a rotating texture. Participants were placed in a situation of perceptual conflict concerning the rotation speed of a cylindrical texture. Participants touched a cylindrical texture of gratings rotating around its axis at a constant speed, while they watched a cylinder without gratings rotating at a different speed on a computer screen. Participants were asked to estimate the speed of the gratings texture under the finger and the spacing (or spatial period) of the gratings. We observed that the tactual estimations of both speed and spacing co-varied with the speed of the visual stimulus, although the cylinder perceived tactually rotated at a constant speed. The first effect (speed effect) could correspond to the resolution of the perceptual conflict in favor of vision. The second effect (spacing effect) is apparently surprising, since no varying information about spacing was provided by vision. However, the physical relation between spacing and speed is well established according to every day experience. Thus, the parameter extraneous to the conflict could be influenced according to previous experience. Such cross-modal effects could be used by designers of virtual reality systems and haptic devices to improve the haptic sensations they can generate using simple (constant) tactile stimulations combined with visual feedback.

PLOS ONE, 2015

Young infants are typically thought to prefer looking at smiling expressions. Although some accou... more Young infants are typically thought to prefer looking at smiling expressions. Although some accounts suggest that the preference is automatic and universal, we hypothesized that it is not rigid and may be influenced by other face dimensions, most notably the face's gender. Infants are sensitive to the gender of faces; for example, 3-month-olds raised by female caregivers typically prefer female over male faces. We presented neutral versus smiling pairs of faces from the same female or male individuals to 3.5-month-old infants (n = 25), controlling for low-level cues. Infants looked longer to the smiling face when faces were female but longer to the neutral face when faces were male, i.e., there was an effect of face gender on the looking preference for smiling. The results indicate that a preference for smiling in 3.5-month-olds is limited to female faces, possibly reflective of differential experience with male and female faces.

Frontiers in psychology, 2015

Angry faces are perceived as more masculine by adults. However, the developmental course and unde... more Angry faces are perceived as more masculine by adults. However, the developmental course and underlying mechanism (bottom-up stimulus driven or top-down belief driven) associated with the angry-male bias remain unclear. Here we report that anger biases face gender categorization toward "male" responding in children as young as 5-6 years. The bias is observed for both own- and other-race faces, and is remarkably unchanged across development (into adulthood) as revealed by signal detection analyses (Experiments 1-2). The developmental course of the angry-male bias, along with its extension to other-race faces, combine to suggest that it is not rooted in extensive experience, e.g., observing males engaging in aggressive acts during the school years. Based on several computational simulations of gender categorization (Experiment 3), we further conclude that (1) the angry-male bias results, at least partially, from a strategy of attending to facial features or their second-orde...

PloS one, 2015

Based on the assumption that good decoding skills constitute a bootstrapping mechanism for readin... more Based on the assumption that good decoding skills constitute a bootstrapping mechanism for reading comprehension, the present study investigated the relative contribution of the former skill to the latter compared to that of three other predictors of reading comprehension (listening comprehension, vocabulary and phonemic awareness) in 392 French-speaking first graders from low SES families. This large sample was split into three groups according to their level of decoding skills assessed by pseudoword reading. Using a cutoff of 1 SD above or below the mean of the entire population, there were 63 good decoders, 267 average decoders and 62 poor decoders. 58% of the variance in reading comprehension was explained by our four predictors, with decoding skills proving to be the best predictor (12.1%, 7.3% for listening comprehension, 4.6% for vocabulary and 3.3% for phonemic awareness). Interaction between group versus decoding skills, listening comprehension and phonemic awareness accoun...

British journal of cancer, 2003

Standard treatment of optic pathways gliomas consists of radiotherapy and surgery when feasible. ... more Standard treatment of optic pathways gliomas consists of radiotherapy and surgery when feasible. Owing to the toxicity of irradiation, chemotherapy has emerged as an interesting therapeutic option, especially in young children. This study describes the neuropsychological profile of 27 children (aged between 1.5 and 15.7 years) with optic pathways gliomas treated with chemotherapy as first-line treatment. Eight of them also received radiotherapy as salvage treatment. Eight had neurofibromatosis type 1 (NF1). Intellectual outcome was preserved in children treated with chemotherapy only (mean=107+/-17) compared to children also receiving radiotherapy (mean IQ=88+/-24) or children having NF1 and treated with chemotherapy (mean IQ=80+/-13). Scores for abstract reasoning, mental arithmetic, chessboard/coding, perception, judgement of line orientation were lower in children irradiated than in those treated only by chemotherapy. Children with Nf1 showed subnormal IQ scores with marked impai...

Neuroreport, Jan 4, 2002

This study addresses the limits of haptic orientation deficit observed in patients with left visu... more This study addresses the limits of haptic orientation deficit observed in patients with left visuo-spatial neglect (VSN) in the fronto-parallel plane. We concentrated on two aspects of the haptic perception of vertical, horizontal and oblique orientations: first, the global level of performances compared with normal subjects and, second, the occurrence of the oblique effect (i.e. lower performances in oblique orientations than in vertical-horizontal orientations). Subjects were asked to position a rod, presented in the fronto-parallel plane, to one of four orientations: vertical, horizontal, left 45 degrees oblique and right 45 degrees oblique. First, we found a haptic orientation deficit in neglect patients: The precision was lower in the neglect patients than in the normal (young adults and seniors) subjects. Second, we observed in both neglect patients and control subjects the occurrence of a similar haptic oblique effect and there were no differences between the results in the l...

This study examined the effect of incorporating a visuo-haptic and haptic (tactual-kinaesthetic) ... more This study examined the effect of incorporating a visuo-haptic and haptic (tactual-kinaesthetic) exploration of letters in a training designed to develop phonemic awareness, knowledge of letters and letter/sound correspondences, on 5-year-old children's understanding and use of the alphabetic principle. Three interventions, which differed in the work on letters identity, were assessed. The letters were explored visually and haptically in "HVAM" training (haptic-visual-auditory-metaphonological), only visually in "VAM" training (visual-auditory-metaphonological) and visually but in a sequential way in "VAM-sequential" training. The three interventions made use of the same phonological exercises. The results revealed that the improvement in the pseudo-word decoding task was higher after HVAM training than after both VAM training and VAM-sequential training (which did not differ). The sequential exploration of the letters (independently of perceptual modalities involved) was not to be sufficient alone for explaining these results. Moreover, similar improvements in the letter recognition test and in the phonological awareness tests were observed after the three interventions. Taken together, the results show that incorporating the visuo-haptic and haptic exploration of letters makes the connections between the orthographic representation of letters and the phonolog- ical representation of the corresponding sounds easier, thus improving the decoding skills of young children.

The problem studied here is how totally blind adults perceive vertical, horizontal, ϩ45º oblique,... more The problem studied here is how totally blind adults perceive vertical, horizontal, ϩ45º oblique, and ϩ135º oblique orientations of a rod in the haptic (tactualkinesthetic) modality. We were interested in examining this spatial property because previous research had shown that the modes of coding orientation may differ according to the perceptual modality. In vision, the vertical and horizontal orientations are always coded more accurately than the oblique orientations. This anisotropy, which Appelle (1972) called the oblique effect, has been found in a wide variety of perceptual tasks (Bryant

Early Human Development, 2014

Background: Very preterm (VP) infants are at greater risk for cognitive difficulties that may per... more Background: Very preterm (VP) infants are at greater risk for cognitive difficulties that may persist during schoolage, adolescence and adulthood. Behavioral assessments report either effortful control (part of executive functions) or emotional reactivity/regulation impairments. Aims: The aim of this study is to examine whether emotional recognition, reactivity, and regulation, as well as effortful control abilities are impaired in very preterm children at 42 months of age, compared with their full-term peers, and to what extent emotional and effortful control difficulties are linked. Study design: Children born very preterm (VP; b 29 weeks gestational age, n = 41) and full-term (FT) agedmatched children (n = 47) participated in a series of specific neuropsychological tests assessing their level of emotional understanding, reactivity and regulation, as well as their attentional and effortful control abilities. Results: VP children exhibited higher scores of frustration and fear, and were less accurate in naming facial expressions of emotions than their aged-matched peers. However, VP children and FT children equally performed when asked to choose emotional facial expression in social context, and when we assessed their selective attention skills. VP performed significantly lower than full terms on two tasks of inhibition when correcting for verbal skills. Moreover, significant correlations between cognitive capacities (effortful control) and emotional abilities were evidenced. Conclusions: Compared to their FT peers, 42 month-olds who were born very preterm are at higher risk of exhibiting specific emotional and effortful control difficulties. The results suggest that these difficulties are linked. Ongoing behavioral and emotional impairments starting at an early age in preterms highlight the need for early interventions based on a better understanding of the relationship between emotional and cognitive difficulties.

Teleoperators and Virtual Environments, 2006

How do we perceive objects when what we see and what we touch is not at the same place? In a virt... more How do we perceive objects when what we see and what we touch is not at the same place? In a virtual environment, we observed that spatial de-location promotes visual dominance instead of visuo-haptic integration when judging the rotation angle of a hand-operated crank. Thus, the de-location of perceptual information appears to increase considerably the weight of the dominant sense at the expenses of the other. We relate this result to the design of teleoperation and virtual reality systems, in which, typically, the visual and haptic sensory information originates in spatially distinct devices. 3 3

PLoS ONE, 2014

Research on emotion showed an increase, with age, in prevalence of positive information relative ... more Research on emotion showed an increase, with age, in prevalence of positive information relative to negative ones. This effect is called positivity effect. From the cerebral analysis of the Late Positive Potential (LPP), sensitive to attention, our study investigated to which extent the arousal level of negative scenes is differently processed between young and older adults and, to which extent the arousal level of negative scenes, depending on its value, may contextually modulate the cerebral processing of positive (and neutral) scenes and favor the observation of a positivity effect with age. With this aim, two negative scene groups characterized by two distinct arousal levels (high and low) were displayed into two separate experimental blocks in which were included positive and neutral pictures. The two blocks only differed by their negative pictures across participants, as to create two negative global contexts for the processing of the positive and neutral pictures. The results show that the relative processing of different arousal levels of negative stimuli, reflected by LPP, appears similar between the two age groups. However, a lower activity for negative stimuli is observed with the older group for both tested arousal levels. The processing of positive information seems to be preserved with age and is also not contextually impacted by negative stimuli in both younger and older adults. For neutral stimuli, a significantly reduced activity is observed for older adults in the contextual block of low-arousal negative stimuli. Globally, our study reveals that the positivity effect is mainly due to a modulation, with age, in processing of negative stimuli, regardless of their arousal level. It also suggests that processing of neutral stimuli may be modulated with age, depending on negative context in which they are presented to. These age-related effects could contribute to justify the differences in emotional preference with age.

Early human development, 2014

Although preterm infants possess early tactile manual abilities, the influence of the postnatal e... more Although preterm infants possess early tactile manual abilities, the influence of the postnatal experience has not yet been systematically examined. To investigate whether early tactile manual habituation, discrimination and recognition (following interference) of shape in preterm infants are modified by postnatal age. Prospective study. Forty preterm infants were assessed from the post-conceptional age (PCA) of 34 weeks. Two groups were made up according to postnatal age (PNA): low PNA (PNA≤10 days of life) and high PNA (PNA≥12 days of life). An object (prism or cylinder) was presented repeatedly in the left hand, and holding times of the object were recorded during each trial. Holding time was shorter for all preterm infants following successive presentation of the same object irrespective of postnatal age range. In the discrimination phase, the mean holding time for the novel object was longer than holding times in the last two habituation trials, in both PNA groups. Finally, the...

Psychologie Francaise - PSYCHOL FR, 2010

We provide here a detailed comparison of the cursive letters drawn by a first-grade child present... more We provide here a detailed comparison of the cursive letters drawn by a first-grade child presenting a developmental coordination disorder (DCD), with those of first-grade children and pre-school children. On the basis of two distinct tasks (copy and dictation of six cursive letters), we estimated the quality of each letter by a quote and measured different parameters to evaluate writing fluidity. We show that for both tasks, the letters of the DCD child are significantly different from those of children of her age, in particular for the dictation task, which requires a mental representation of the letter. The more discriminative parameters between the tracks of the DCD child and those of children of her age are length and speed.

The Quarterly Journal of Experimental Psychology Section A, 2004

Four-month-old infants were allowed to manipulate, without vision, two rings attached to a bar th... more Four-month-old infants were allowed to manipulate, without vision, two rings attached to a bar that permitted each ring to undergo rotary motion against a fixed surface. In different conditions, the relative motions of the rings were rigid, independent, or opposite, and they circled either the same fixed point outside the zone of manipulation or spatially separated points. Infants' perception of the ring assemblies were affected by the nature of the rotary motion in two ways. First, infants perceived a unitary object when the felt ends of the object underwent a common, rigid rotary motion; perception of object unity was stronger in this condition than when the ends underwent either independent or opposite rotary motions. Second, infants perceived two distinct objects when the felt ends of the objects underwent independent rotary motions that centred on distinct fixed points. Perception of the distinctness of the objects was less clear when the ends underwent opposite or independent rotary motions that centred on a common fixed point. These findings provide the first evidence that infants are sensitive to rotary motion patterns and can extrapolate a global pattern of rigid motion from the distinct, local velocities that they produce and experience at their two hands.

The Quarterly Journal of Experimental Psychology Section A, 2001

This study investigates whether the vertical orientation may be predominantly used as an amodal r... more This study investigates whether the vertical orientation may be predominantly used as an amodal reference norm by the visual, haptic, and somato-vestibular perceptual systems to define oblique orientations. We examined this question by asking the same sighted adult subjects to reproduce, in the frontal (roll) plane, the vertical (0°) and six oblique orientations in three tasks involving different perceptual systems. In the visual task, the subjects adjusted a moveable rod so that it reproduced the orientation of a visual rod seen previously in a dark room. In the haptic task, the blindfolded sighted subjects scanned an oriented rod with one hand and reproduced its orientation, with the same hand, on a moveable response rod. In the somato-vestibular task, the blindfolded sighted subjects, sitting in a rotating chair, adjusted this chair in order to reproduce the tested orientation of their own body. The results showed that similar oblique effects (unsigned angular error difference between six oblique orientations and vertical orientation) were observed across the three tasks. However, there were no positive correlations between the visual, haptic, Requests for reprints should be sent to EdouardGentaz,

Psychonomic Bulletin & Review, 2004

This article surveys studies of the occurrence, in the haptic modality, of three geometrical illu... more This article surveys studies of the occurrence, in the haptic modality, of three geometrical illusions well known in vision, and it discusses the nature of the processes underlying these haptic illusions. We argue that the apparently contradictory results found in the literature concerning them may be explained, at least partially, by the characteristicsof manual exploratory movements. The Müller-Lyer illusion is present in vision and in haptics and seems to be the result of similar processes in the two modalities. The vertical-horizontal illusion also exists in vision and haptics but is due partly to similar processes (bisection) and partly to processes specific to each modality (anisotropy of the visual field and overestimation of radial vs. tangential manual exploratory movements). The Delboeuf illusion seems to occur only in vision, probably because exploration by the index finger may exclude the misleading context from tactile perception. The role of these haptic exploratory movements may explain why haptics is as sensitive as vision to certain illusions and less sensitive to others.