Massimiliano Di Luca

University of Birmingham · School of Psychology

The environment has a temporal structure, and knowing when a stimulus will appear translates into increased perceptual performance. Here we investigated how the human brain exploits temporal regularity in stimulus sequences for perception. We find that the timing of stimuli that occasionally deviate from a regularly paced sequence is perceptually d...

When planning interactions with nearby objects, our brain uses visual information to estimate shape, material composition, and surface structure before we come into contact with them. Here we analyse brain activations elicited by different types of visual appearance, measuring fMRI responses to objects that are glossy, matte, rough, or textured. In...

Distortions of perceived duration can give crucial insights into the mechanisms that underlie the processing and representation of stimulus timing. One factor that affects duration estimates is the temporal structure of stimuli that fill an interval. For example, regular filling (isochronous interval) leads to an overestimation of perceived duratio...

The last quarter of a century has seen a dramatic rise of interest in the spatial constraints on multisensory integration. However, until very recently, the majority of this research has investigated integration in the space directly in front of the observer. The space around us, however, extends in three spatial dimensions in the front and to the...

Crossmodal judgments of relative timing commonly yield a non-zero point of subjective simultaneity (PSS). Here, we test whether subjective simultaneity is coherent across all pair-wise combinations of the visual, auditory, and tactile modalities. To this end, we examine PSS estimates for transitivity: if stimulus A has to be presented x ms before s...

When musicians play in ensemble, they continuously adapt to each other to ensure that the group keeps time together. This adaptation can be captured by a linear phase correction model, representing how they adjust to one another. The Augmented Reality Musical Ensemble (ARME) project is building a system for solo musicians to practise with a virtual...

[This corrects the article DOI: 10.1016/j.isci.2023.106180.].

Self-touch plays a central role in the construction and plasticity of the bodily self. But which mechanisms support this role? Previous accounts emphasize the convergence of proprioceptive and tactile signals from the touching and the touched body parts. Here, we hypothesise that proprioceptive information is not necessary for self-touch modulation...

Optical markerless hand-tracking systems incorporated into virtual reality (VR) headsets are transforming the ability to assess fine motor skills in VR. This promises to have far-reaching implications for the increased applicability of VR across scientific, industrial, and clinical settings. However, so far, there are little data regarding the accu...

Detailed hand motions play an important role in face-to-face communication to emphasize points, describe objects, clarify concepts, or replace words altogether. While shared virtual reality (VR) spaces are becoming more popular, these spaces do not, in most cases, capture and display accurate hand motions. In this paper, we investigate the conseque...

Key points: Ageing effects on tactile perception involve the deterioration of spatial sensitivity, although the contribution of central and peripheral factors is not clear. We combined psychophysics, measurements of finger properties, modelling, and simulation of the response of first-order tactile neurons to investigate to what extent skin elasti...

With sliding contact humans are able to perceive tactile features at the micron scale, such as a single dot raised only few microns when placed on a smooth surface. Frictional effects are important in determining the tactile cues available in sliding and depend on a variety of factors. In this study, we investigated how detection sensitivity to a s...

Onset detection is the process of identifying the start points of musical note events within an audio recording. While the detection of percussive onsets is often considered a solved problem, soft onsets-as found in string instrument recordings-still pose a significant challenge for state-of-the-art algorithms. The problem is further exacerbated by...

We review four current computational models that simulate the response of mechanoreceptors in the glabrous skin to tactile stimulation. The aim is to inform researchers in psychology, sensorimotor science and robotics who may want to implement this type of quantitative model in their research. This approach proves relevant to understanding of the i...

We propose a haptic system for virtual manipulation to provide feedback on the user's forearm instead of the fingertips. In addition to visual rendering of the manipulation with virtual fingertips, we employ a device to deliver normal or shear skin-stretch at multiple points near the wrist. To understand how design parameters influence the experien...

Despite non-co-location, haptic stimulation at the wrist can potentially provide feedback regarding interactions at the fingertips without encumbering the user's hand. Here we investigate how two types of skin deformation at the wrist (normal and shear) relate to the perception of the mechanical properties of virtual objects. We hypothesized that a...

Optical marker-less hand-tracking systems incorporated into virtual reality (VR) headsets are transforming the ability to assess motor skills, including hand movements, in VR. This promises to have far-reaching implications for the increased applicability of VR across scientific, industrial and clinical settings. However, so far, there is little da...

Our aim is to provide effective interaction with virtual objects, despite the lack of co-location of virtual and real-world contacts, while taking advantage of relatively large skin area and ease of mounting on the forearm. We performed two human participant studies to determine the effects of haptic feedback in the normal and shear directions duri...

Touch interactions are central to many human activities, but there are few technologies for computationally augmenting free-hand interactions with real environments. Here, we describe Tactile Echoes, a finger-wearable system for augmenting touch interactions with physical objects. This system captures and processes touch-elicited vibrations in re...

The synthesis of realistic robot grasps in a simulated environment is pivotal in generating datasets that support sim-to-real transfer learning. In a step toward achieving this goal, we propose PrendoSim, an open-source grasp generator based on a proxy-hand simulation that employs NVIDIA’s physics engine (PhysX) and the recently released articulate...

We examined the contributions of kinesthetic and skin stretch cues to static weight perception. In three psychophysical experiments, several aspects of static weight perception were assessed by asking participants either to detect on which hand a weight was presented or to compare between two weight cues. Two closed-loop controlled haptic devices w...

Causality poses clear constraints to the timing of sensory signals produced by events, as sound travels slower than light, causing auditory stimulation to lag visual stimulation. Previous studies show that implied causality between unrelated events can change the tolerance of simultaneity judgements for audio-visual asynchronies. Here, we tested wh...

Causality poses explicit constraints to the timing of sensory signals produced by events, as sound travels slower than light, making auditory stimulation to lag visual stimulation. Previous studies show that implied causality between unrelated events can change the tolerance of simultaneity judgments for audiovisual asynchronies. Here, we tested wh...

Roughness perception through fingertip contact with a textured surface can involve spatial and temporal cues from skin indentation and vibration respectively. Both types of cue may be affected by contact forces when feeling a surface and we ask whether, on a given trial, discrimination performance relates to contact forces. We examine roughness dis...

We propose a haptic system that applies forces or skin deformation to the user's arm, rather than at the fingertips, for believable interaction with virtual objects as an alternative to complex thimble devices. Such a haptic system would be able to convey information to the arm instead of the fingertips, even though the user manipulates virtual obj...

As an alternative to thimble devices for the fingertips, we investigate haptic systems that apply stimulus to the user's forearm. Our aim is to provide effective interaction with virtual objects, despite the lack of co-location of virtual and real-world contacts, while taking advantage of relatively large skin area and ease of mounting on the forea...

The temporal profile of one’s movement and its associated tactile feedback is a key component in a successful exploration of surfaces of the object. The implementation of haptics in virtual systems facilitates the scientific investigation of characteristics ofaction and movement. However, most haptic systems are subject to unavoidable rendering...

The creation and delivery of haptic force-feedback that conveys the impression of touching an object can be challenging because the signal needs to be perceived to be lawfully coupled to user’s actions. The generation and delivery of haptic feedback could take time, and the delay can become perceivable. Here we examine what is the minimum detectabl...

In this work, we investigate the influence of different visualizations on a manipulation task in virtual reality (VR). Without the haptic feedback of the real world, grasping in VR might result in intersections with virtual objects. As people are highly sensitive when it comes to perceiving collisions, it might look more appealing to avoid intersec...

To cite this paper: Lorenzo Scalera, Stefano Seriani, Paolo Gallina, Massimiliano Di Luca, and Alessandro Gasparetto. An experimental setup to test dual-joystick directional responses to vibrotactile stimuli. IEEE Transactions on Haptics, 11(3):378–387, 2018.

The deployment of visual spatial attention can be significantly influenced in an exogenous, presumably bottom-up manner. Traditionally, spatial cueing paradigms have been utilized to come to such conclusions. Although these paradigms have primarily made use of visual cues, spatially correspondent tactile cues have also been successfully employed. H...

Exposure to a particular sensory stimulation for a prolonged period of time often results in changes in the associated perception of subsequent stimulation. Such changes can take the form of decreases in sensitivity and/or aftereffects. Aftereffects often result in a rebound in the perception of the associated stimulus property when presented with...

Abstract It has been suggested that the integration of multiple body-related sources of information within the peri-personal space (PPS) scaffolds body ownership. However, a normative computational framework detailing the functional role of PPS is still missing. Here we cast PPS as a visuo-proprioceptive Bayesian inference problem whereby objects w...

Hand tracking and haptics are gaining more importance as key technologies of virtual reality (VR) systems. For designing such systems, it is fundamental to understand how the appearance of the virtual hands influences user experience and how the human brain integrates vision and haptics. However, it is currently unknown whether multi-sensory integr...

The ability to discriminate temporal intervals in the milliseconds-to-seconds range has been accounted for by proposing that duration is encoded in the dynamic change of a neuronal network state. A critical limitation of such networks is that their activity cannot immediately return to the initial state, a restriction that could hinder the processi...

Two joystick-based teleoperation is a common method for controlling a remote machine or a robot. Their use could be counter-intuitive and could require a heavy mental workload. The goal of this paper is to investigate whether vibrotactile prompts could be used to trigger dual-joystick responses quickly and intuitively, so to possibly employ them fo...

Two joystick-based teleoperation is a common method for controlling a remote machine or a robot. Their use could be counter-intuitive and could require a heavy mental workload. The goal of this paper is to investigate whether vibrotactile prompts could be used to trigger dual-joystick responses quickly and intuitively, so to possibly employ them fo...

Two joystick-based teleoperation is a common method for controlling a remote machine or a robot. Their use could be counter-intuitive and could require a heavy mental workload. The goal of this paper is to investigate whether vibrotactile prompts could be used to trigger dual-joystick responses quickly and intuitively, so to possibly employ them fo...

Timing and Time Perception: Procedures, Measures, and Applications is a one-of-a-kind, collective effort to present the most utilized and known methods on timing and time perception. Specifically, it covers methods and analysis on circadian timing, synchrony perception, reaction/response time, time estimation, and alternative methods for clinical/d...

In this paper we investigate the influence of the location of vibrotactile stimulation in triggering the response made using two handheld joysticks. In particular, we compare performance with stimuli delivered either using tactors placed on the palm or on the back of the hand and with attractive (move toward the vibration) or repulsive prompts (mov...

Predicting the time of stimulus onset is a key component in perception. Previous investigations of perceived timing have focused on the effect of stimulus properties such as rhythm and temporal irregularity, but the influence of non-temporal properties and their role in predicting stimulus timing has not been exhaustively considered. The present st...

In this paper we investigate the influence of the location of vibrotactile stimulation in triggering the response made using two handheld joysticks. In particular, we compare performance with stimuli delivered either using tactors placed on the palm or on the back of the hand and with attractive (move toward the vibration) or repulsive prompts (mov...

It's reasonable to assume that a regularly paced sequence should be perceived as regular, but here we show that perceived regularity depends on the context in which the sequence is embedded. We presented one group of participants with perceptually regularly paced sequences, and another group of participants with mostly irregularly paced sequences (...

The visual impression of an object's surface reflectance ('gloss') relies on a range of visual cues, both monocular and binocular. While previous imaging work has identified processing within ventral visual areas as important for monocular cues, little is known about cortical areas involved in processing binocular cues. Here we used human functiona...

An isochronous sequence is a series of repeating events with the same inter-onset-interval. A common finding, is that as a the length of a sequence increases, so does temporal sensitivity to irregularities – that is, the detection of deviations from isochrony is better with a longer sequence. Several theoretical accounts exist in the literature as...

Variations in the temporal structure of an interval can lead to remarkable differences in perceived duration. For example, it has previously been shown that isochronous intervals, that is, intervals filled with temporally regular stimuli, are perceived to last longer than intervals left empty or filled with randomly timed stimuli. Characterizing th...

INTRODUCTION Distortions of perceived duration due to factors other than the physical duration of the interval give crucial insights into the computational and neural mechanisms underlying duration perception. One source of such distortions can be the temporal structure of interval filler stimuli. Recently, Horr and Di Luca [1] demonstrated that is...

Surface gloss information conveyed by image cues (i.e., highlights) has been shown to be processed in ventral and dorsal areas. In this study we used fMRI to distinguish the brain areas that selectively process 2D and 3D cues about surface gloss. We performed one experiment using 2D images of random objects with glossy surfaces where diffuse highli...

The ability to estimate temporal properties like interval duration is crucial for our successful interaction with the environment. Quantifying how factors other than physical duration can distort duration estimates helps understanding the mechanisms underlying temporal perception. Previous research has shown that intervals defined by two temporal m...

Duration estimates are influenced by the stimuli defining a temporal interval as well as by its filling. Not only does perceived duration increase with the number of short signals between an interval’s beginning and end marker (e.g., Buffardi, 1971, Perception & Psychophysics, 10, 292-294), but also the temporal structure of such filler signals mak...

In multisensory reaction time paradigms the modality-shifting effect (MSE) refers to the finding that simple reaction times to stimuli in one modality are quicker when the previous trial required a reaction to the same modality (e.g., Spence et al., 2001, Perception & Psychophysics, 330-336; Sutton et al., 1961, The American Journal of Psychology,...

There is a well-known tradeoff between speed and accuracy in judgments made under uncertainty. Diffusion models have been proposed to capture the increase in response time for more uncertain decisions and the change in performance due to a prioritization of speed or accuracy in the responses. Experimental paradigms have been confined to the visual...

Surface gloss is an important cue to the material properties of objects. Recent progress in the study of macaque's brain has increased our understating of the areas involved in processing information about gloss, however the homologies with the human brain are not yet fully understood. Here we used human functional magnetic resonance imaging (fMRI)...

In this work we investigate how judgments of perceived duration are influenced by the properties of the signals that define the intervals. Participants compared two auditory intervals that could be any combination of the following four types: intervals filled with continuous tones (filled intervals), intervals filled with regularly-timed short tone...

The ability to estimate temporal properties like the duration of an interval is an important cognitive function crucial for our successful interaction with the environment. Characterising quantitatively how factors other than physical duration distort duration estimates can help us in understanding the mechanisms underlying temporal perception. Her...

In this paper we discuss the concept of co-adaptation between a human operator and a machine interface and we summarize its application with emphasis on two different domains, teleoperation and assistive technology. The analysis of the literature reveals that only in a few cases the possibility of a temporal evolution of the co-adaptation parameter...

Surface gloss is an important cue to the material properties of objects. Recent progress in the study of macaque's brain has increased our understating of the areas involved in processing information about gloss, however the homologies with the human brain are not yet fully understood. Here we used human functional magnetic resonance imaging (fMRI)...

A commonly observed phenomenon to elucidate distortions of perceived duration is the filled-duration illusion: a temporal interval delimited by two marker signals is perceived to be shorter than the same interval with several identical filler signals. Previous investigations have focused on regularly spaced (isochronous) fillers and the influence o...

We perceive compliance of deformable objects using several sources of sensory information obtained during the manual interaction. Some signals are inherently informative about how soft an object is. For example, softness of objects with deformable surfaces can be estimated directly from the pattern of skin deformation over time. On the other hand,...

What is the apparent softness of a grasped object composed of two compliant materials? Experimental data indicates that perceived softness of a composite object depends on how the object is grasped and how it is oriented. If the object is grasped with a precision grip using index and thumb, turning around the object leads to a consistent change in...

For the perception of haptic environmental properties such as stiffness, damping, or inertia, estimates of force and movement must be combined continuously over time. We investigate the relations between sensitivity of perceptual judgments about force and the time a perceptual response is given with different types of hand movements. Portions of re...

If the audio and visual stream in a movie are poorly aligned the discrepancy between the actors’ speech and lip movements are very disturbing in the beginning. However, after a short time the constant delay in one modality becomes barely noticeable. This phenomenon is termed temporal recalibration, that is, the adaptation of synchrony perception to...

The perception of interval duration can be distorted by a multitude of factors related to stimulus characteristics. One of them is the filled-duration illusion, where filled intervals are perceived to be longer than their empty counterparts. The filled-duration illusion has been shown to occur with intervals consisting of one continuous signal (e.g...

Often multisensory information is integrated in a statistically optimal fashion where each sensory source is weighted according to its precision. This integration scheme isstatistically optimal because it theoretically results in unbiased perceptual estimates with the highest precisionpossible.There is a current lack of consensus about how the nerv...

Human observers acquire information about physical properties of the environment through different sensory modalities. Temporal coincidence of sensory information has been identified as an important cue to aid the organization of signals into a coherent representation of events. Perceived simultaneity, successiveness, and temporal order are thus im...

Sequences of regularly spaced stimuli carry information about the timing and properties of future stimuli. Here we investigated how these expectations can affect the perceived time of stimuli and we propose a model based on the Bayesian framework. Expectation of when a future stimulus is to occur is modelled as the prior probability of a stimulus o...