Tactile shape discrimination for moving stimuli.

In this study, we explored spatial-temporal dependencies and their impact on the tactile perception of moving objects. Building on previous research linking visual perception and human movement, we examined if an imputed motion mechanism operates within the tactile modality. We focused on how biological coherence between space and time, characteristic of human movement, influences tactile perception. An experiment was designed wherein participants were stimulated on their right palm with tactile patterns, either ambiguous (incongruent conditions) or non-ambiguous (congruent conditions) relative to a biological motion law (two-thirds power law) and asked to report perceived shape and associated confidence. Our findings reveal that introducing ambiguous tactile patterns (1) significantly diminishes tactile discrimination performance, implying motor features of shape recognition in vision are also observed in the tactile modality, and (2) undermines participants' response confidence, uncovering the accessibility degree of information determining the tactile percept's conscious representation. Analysis based on the Hierarchical Drift Diffusion Model unveiled the sensitivity of the evidence accumulation process to the stimulus's informational ambiguity and provides insight into tactile perception as predictive dynamics for reducing uncertainty. These discoveries deepen our understanding of tactile perception mechanisms and underscore the criticality of predictions in sensory information processing.

Information-Theoretic Approaches in EEG Correlates of Auditory Perceptual Awareness under Informational Masking.

In informational masking paradigms, the successful segregation between the target and masker creates auditory perceptual awareness. The dynamics of the build-up of auditory perception is based on a set of interactions between bottom-up and top-down processes that generate neuronal modifications within the brain network activity. These neural changes are studied here using event-related potentials (ERPs), entropy, and integrated information, leading to several measures applied to electroencephalogram signals. The main findings show that the auditory perceptual awareness stimulated functional activation in the fronto-temporo-parietal brain network through (i) negative temporal and positive centro-parietal ERP components; (ii) an enhanced processing of multi-information in the temporal cortex; and (iii) an increase in informational content in the fronto-central cortex. These different results provide information-based experimental evidence about the functional activation of the fronto-temporo-parietal brain network during auditory perceptual awareness.

Active self-motion control and the role of agency under ambiguity.

Purpose: Self-motion perception is a key factor in daily behaviours such as driving a car or piloting an aircraft. It is mainly based on visuo-vestibular integration, whose weighting mechanisms are modulated by the reliability properties of sensory inputs. Recently, it has been shown that the internal state of the operator can also modulate multisensory integration and may sharpen the representation of relevant inputs. In line with the concept of agency, it thus appears relevant to evaluate the impact of being in control of our own action on self-motion perception. Methodology: Here, we tested two conditions of motion control (active/manual trigger versus passive/ observer condition), asking participants to discriminate between two consecutive longitudinal movements by identifying the larger displacement (displacement of higher intensity). We also tested motion discrimination under two levels of ambiguity by applying acceleration ratios that differed from our two "standard" displacements (i.e., 3 s; 0.012 m.s-2 and 0.030 m.s-2). Results: We found an effect of control condition, but not of the level of ambiguity on the way participants perceived the standard displacement, i.e., perceptual bias (Point of Subjective Equality; PSE). Also, we found a significant effect of interaction between the active condition and the level of ambiguity on the ability to discriminate between displacements, i.e., sensitivity (Just Noticeable Difference; JND). Originality: Being in control of our own motion through a manual intentional trigger of self-displacement maintains overall motion sensitivity when ambiguity increases.

Investigating the influence of masker and target properties on the dynamics of perceptual awareness under informational masking.

Informational masking has been investigated using the detection of an auditory target embedded in a random multi-tone masker. The build-up of the target percept is influenced by the masker and target properties. Most studies dealing with discrimination performance neglect the dynamics of perceptual awareness. This study aims at investigating the dynamics of perceptual awareness using multi-level survival models in an informational masking paradigm by manipulating masker uncertainty, masker-target similarity and target repetition rate. Consistent with previous studies, it shows that high target repetition rates, low masker-target similarity and low masker uncertainty facilitate target detection. In the context of evidence accumulation models, these results can be interpreted by changes in the accumulation parameters. The probabilistic description of perceptual awareness provides a benchmark for the choice of target and masker parameters in order to examine the underlying cognitive and neural dynamics of perceptual awareness.

Being active over one's own motion: Considering predictive mechanisms in self-motion perception.

Self-motion perception is a key element guiding pilots' behavior. Its importance is mostly revealed when impaired, leading in most cases to spatial disorientation which is still today a major factor of accidents occurrence. Self-motion perception is known as mainly based on visuo-vestibular integration and can be modulated by the physical properties of the environment with which humans interact. For instance, several studies have shown that the respective weight of visual and vestibular information depends on their reliability. More recently, it has been suggested that the internal state of an operator can also modulate multisensory integration. Interestingly, the systems' automation can interfere with this internal state through the loss of the intentional nature of movements (i.e., loss of agency) and the modulation of associated predictive mechanisms. In this context, one of the new challenges is to better understand the relationship between automation and self-motion perception. The present review explains how linking the concepts of agency and self-motion is a first approach to address this issue.

Optical and gravito-inertial contributions to the perception and control of height in a simulated Low-Altitude Flight context.

Low-Altitude Flight (LAF) is a flight formation consisting of rapid close ground flight. Perception and control of self-motion, allowing for optimal information collection and rapid adaptation, are of fundamental importance during LAF, but remain largely unexplored. This study aimed to analyse the impact of visuo-vestibular stimuli on the monitoring of height in a motion-based simulated LAF context. Thirteen non-pilots were tested in different environmental conditions, in which optical and gravito-inertial (GI) information were manipulated. The visual environment, displayed with a VR headset, was a low-textured landscape with identical and equally spaced trees throughout the trials. The GI environment was designed thanks to a motion-based simulator. Results showed that participants had better performances in a visuo-vestibular environment than in a visual-only setting, indicating that multi-sensory information was picked-up faster than a mono-sensory structure. Additionally, we found differences in the contribution of vestibular inputs depending on the kind of task. Practitioner summary: Low-Altitude-Flight (LAF) manoeuvres require delicate aircraft control. Two experiments using a large flight simulator investigated how visual and vestibular stimulation contribute to LAF perception and control. Results suggest that both sources of stimulation need to be combined for accurate performance, with consequences for simulator-based training scenarios. Abbreviations: LAF: low altitude flight; GI: gravito-inertial; 1/2/3D: 1/2/3 dimensions; VR: virtual reality; Mvt: movement; GVE: good visual environment; DVE: degraded visual environment; SSQ: simulator motion sickness questionnary; RT: reaction time; DIMSS: dynamic interface modelling and simulation system metric; corrAcf: maximum correlation coefficient; corrLag: maximum correlation lag; DFT: deviation from target; StdJ: standard deviation of the joytick value; NCR: number of control reversal.

Ebbinghaus figures that deceive the eye do not necessarily deceive the hand.

In support of the visual stream dissociation hypothesis, which states that distinct visual streams serve vision-for-perception and vision-for-action, visual size illusions were reported over 20 years ago to 'deceive the eye but not the hand'. Ever since, inconclusive results and contradictory interpretations have accumulated. Therefore, we investigated the effects of the Ebbinghaus figure on repetitive aiming movements with distinct dynamics. Participants performed a Fitts' task in which Ebbinghaus figures served as targets. We systematically varied the three parameters which have been shown to influence the perceived size of the Ebbinghaus figure's target circle, namely the size of the target, its distance to the context circles and the size of the context circles. This paper shows that movement is significantly affected by the context size, but, in contrast to perception, not by the other two parameters. This is especially prominent in the approach phase of the movement towards the target, regardless of the dynamics. To reconcile the findings, we argue that different informational variables are used for size perception and the visual control of movements irrespective of whether certain variables induce (perceptual) illusions.

Quantifying the Ebbinghaus figure effect: target size, context size, and target-context distance determine the presence and direction of the illusion.

Over the last 20 years, visual illusions, like the Ebbinghaus figure, have become widespread to investigate functional segregation of the visual system. This segregation reveals itself, so it is claimed, in the insensitivity of movement to optical illusions. This claim, however, faces contradictory results (and interpretations) in the literature. These contradictions may be due to methodological weaknesses in, and differences across studies, some of which may hide a lack of perceptual illusion effects. Indeed, despite the long history of research with the Ebbinghaus figure, standardized configurations to predict the illusion effect are missing. Here, we present a complete geometrical description of the Ebbinghaus figure with three target sizes compatible with Fitts' task. Each trial consisted of a stimulus and an isolated probe. The probe was controlled by the participant's response through a staircase procedure. The participant was asked whether the probe or target appeared bigger. The factors target size, context size, target-context distance, and a control condition resulted in a 3 × 3 × 3+3 factorial design. The results indicate that the illusion magnitude, the perceptual distinctiveness, and the response time depend on the context size, distance, and especially, target size. In 33% of the factor combinations there was no illusion effect. The illusion magnitude ranged from zero to (exceptionally) 10% of the target size. The small (or absent) illusion effects on perception and its possible influence on motor tasks might have been overlooked or misinterpreted in previous studies. Our results provide a basis for the application of the Ebbinghaus figure in psychophysical and motor control studies.

A multi-level approach to investigate the control of an input device: application to a realistic pointing task.

This study investigates the subjects' performance during realistic conditions of control of a joystick. An adapted reciprocal aiming task consisting in driving a virtual vehicle along a slalom course as fast as possible was performed while accuracy constraints were manipulated. Realistic dynamical Interface Screen Relationship between the joystick displacements and the displacements of the vehicle was simulated. Vehicle displacements and motor activity (muscle activity and joint kinematics) were recorded. The results highlighted the applicability of the Fitts' law to more realistic conditions where the use of an input device is performed in an intensive control situation. Besides, biomechanical results suggested that neuromuscular responses were different regarding the direction of movement, whereas the performance at a behavioural level were not affected. Thus, this study demonstrates the interest in considering two different aspects of the user's performance (behavioural and biomechanical ones) to make a better agreement between the device design and users' needs. PRACTITIONER SUMMARY: This study considered two different aspects of the subject's performance in a realistic situation of speed­accuracy trade-off: the behavioural and motor activity. The necessity for the design of the future ergonomics pointing devices to meet the expectations of the neuromuscular system in order to facilitate their uses is highlighted.

Influence of task constraints and device properties on motor patterns in a realistic control situation.

The influences of task difficulty (index difficulty: 2-4), input device of different length, range of motion and mode of resistance (joystick or rotorcraft stick), and directions of movement (leftward rightward) on motor patterns in a realistic control situation were examined with a multilevel analysis (joint kinematics and muscular variables, and global task performance). Eight subjects controlled the displacements of a virtual object during a slalom task characterized by a realistic inertial model. Pilots adapted the endpoint kinematic organization to increasing accuracy constraints to preserve task success whatever the device and the direction. However, the rotorcraft stick manipulation remains highly complex in comparison to the joystick due to poorer proprioceptive information, higher inertial constraints, and an asymmetrical muscle control.

Automation technology and sense of control: a window on human agency.

Previous studies have shown that the perceived times of voluntary actions and their effects are perceived as shifted towards each other, so that the interval between action and outcome seems shortened. This has been referred to as 'intentional binding' (IB). However, the generality of this effect remains unclear. Here we demonstrate that Intentional Binding also occurs in complex control situations. Using an aircraft supervision task with different autopilot settings, our results first indicated a strong relation between measures of IB and different levels of system automation. Second, measures of IB were related to explicit agency judgement in this applied setting. We discuss the implications for the underlying mechanisms, and for sense of agency in automated environments.

Structuring process and closure principle in spatial and temporal reproduction tasks.

The goal of the experiment reported was to replicate the previous Sarrazin's (2000) study in order to verify, with an adequate methodological procedure, whether or not the closure principle applied in spatial and temporal reproduction tasks. The hypothesis defended was that the closure of the pattern is an intrinsic property of the structuring process in spatial memory. The stimuli consisted of eight visually presented dots that appeared sequentially with inter-dot distances corresponding to inter-dot durations. After a learning phase, participants reproduced the spatial (space condition) or temporal (time condition) characteristics of the target 60 times in succession. We analyzed the variance level for both element location and Inter-Element-Interval (IEI) on spatial and temporal responses. Two main results emerge from this experiment: (1) the critical dependency of the closure principle to the nature (spatial or temporal) of the response, (2) the importance to consider both locations and intervals as complementary information. These results are discussed in the light of physical system, in particular in term of compensation phenomenon and we proposed a mathematical model that replicates the qualitative feature of variance for both space and time conditions.

Coupling kinematics of memory and kinematics of movement: the conditions for a psychological relativity.

The organization of spatial and temporal information relative to memory-movement interactions was studied in a recall task. Stimuli consisted of four different configurations of eight dots, presented sequentially. In two configurations, the stimuli were spatiotemporal congruent, with (constant or variable) inter-stimulus distances corresponding to (constant or variable) inter-stimulus time intervals. In the other two configurations, the stimuli were spatiotemporal incongruent, with (constant or variable) inter-stimulus distances not corresponding to (variable or constant) inter-stimulus time intervals. After a learning phase consisting of 20 presentations of the target configuration, participants performed a series of pointing movements to reproduce both spatial and temporal characteristics of the stimulus 60 times in succession without ever re-examining the target configuration. Classically, in incongruent spatiotemporal conditions, the reproduction of, respectively, constant distances or constant time intervals are strongly disturbed by the simultaneous perception of variable inter-stimulus time intervals (Tau effect) or variable distances (Kappa effect). We assume that these spatiotemporal dependencies, which occur when the response relates to one dimension only, crucially depend on the non-integration of motoric aspects in memory.

How do we know what we are doing? Time, intention and awareness of action.

Time is a fundamental dimension of consciousness. Many studies of the "sense of agency" have investigated whether we attribute actions to ourselves based on a conscious experience of intention occurring prior to action, or based on a reconstruction after the action itself has occurred. Here, we ask the same question about a lower level aspect of action experience, namely awareness of the detailed spatial form of a simple movement. Subjects reached for a target, which unpredictably jumped to the side on some trials. Participants (1) expressed their expectancy of a target shift during the upcoming movement, (2) pointed at the target as quickly and accurately as possible before returning to the start posiment to the target shift if required and (3) reproduced the spatial path of the movement they had just made, as accurately as possible, to give an indication of their awareness of the pointing movement. We analysed the spatial disparity between the initial and the reproduced movements on those with a target shift. A negative disparity value, or undershoot, suggests that motor awareness merely reflects a sluggish record of coordinated motor performance, while a positive value, or overshoot, suggests that participants' intention to point to the shifting target contributes more to their awareness of action than their actual pointing movement. Undershoot and overshoot thus measure the reconstructive (motoric) and the preconstuctive (intentional) aspects of action awareness, respectively. We found that trials on which subjects strongly expected a target shift showed greater overshoot and less undershoot than trials with lower expectancy. Conscious expectancy therefore strongly influences the experience of the detailed motor parameters of our actions. Further, a delay inserted either between the expectancy judgement and the pointing movement, or between the pointing movement and the reproduction of the movement, had no effect on visuomotor adjustment but strongly influenced action awareness. Delays during either interval boosted undershoots, suggesting increased reliance on a time-limited sensory memory for action. The experience of action is thus strongly influenced by prior thoughts and expectations, but only over a short time period. Thus, awareness of our actions is a dynamic and relatively flexible mixture of what we intend to do, and what our motor system actually does.

Dynamics of visuo-spatial remembering: a study of information structuring in memory.

We studied the process by which learning a pattern of motor activity reaches a steady-state characterized by a reduction in fluctuations. The stimuli consisted of eight visually presented dots that appeared sequentially. In a 20-trial learning phase, participants reproduced the positions of the eight dots after each presentation. Next, they reproduced the pattern 40 times without renewed presentation. In one condition, spatial distances between the dots were proportional to the intervals between their appearances; in the other they were not proportional. We analyzed how the reproduction stabilized at the configuration and dot levels. In proportional as well as non-proportional conditions, stabilization occurs at different time scales for the configuration and dot levels. The stabilization rate differed between proportional and non-proportional conditions. These results are discussed in the framework of dynamical systems.

Time, action, and consciousness.

Time plays a central role in consciousness, at different levels and in different aspects of information processing. Subliminal perception experiments demonstrate that stimuli presented too briefly to enter conscious awareness are nevertheless processed to some extent. Implicit learning, implicit memory, and conditioning studies suggest that the extent to which memory traces are available for verbal report and for cognitive control is likewise dependent on the time available for processing during acquisition. Differences in the time available for processing also determine not only the extent to which one becomes conscious of action, but also provides the basis for making attributions of authorship to experienced acts. In this paper, we offer a brief overview of these different findings and suggest that they can all be understood based on the fact that consciousness takes time. From this perspective, the availability of representations to conscious awareness depends on the quality of these representations - the extent to which they are strong, stable in time, and distinctive. High-quality representations occur when processes of global competition have had sufficient time to operate so as to make the system settle into the best possible interpretation of the input. Such processes implement global constraint satisfaction and critically depend on reentrant processing, through which representations can be further enriched by high-level constraints. We discuss these ideas in light of current theories of consciousness, emphasizing the fact that consciousness should be viewed as a process rather than as a static property associated with some states and not with others.

Tau and Kappa effects in physical space: the case of audition.

The organization of spatio-temporal information in an auditory memory task was studied in two experiments. Stimuli consisted of four different configurations of eight sequentially presented beeps. In two configurations, the stimuli were space-time congruent, with (constant or variable) inter-stimulus distances corresponding to (constant or variable) inter-stimulus time intervals. In the other two configurations, the stimuli were space-time incongruent, with (constant or variable) inter-stimulus distances not corresponding to (variable or constant) inter-stimulus time intervals. After a learning phase consisting of 20 presentations of the target configuration, participants reproduced the spatial (Experiment 1) or temporal (Experiment 2) characteristics of the target 60 times in succession without re-examining the target configuration. Accuracy (with respect to the target) and variability (between responses) were found to evolve independently. In the incongruent space-time conditions, effects of variable inter-stimulus time intervals or distances on the reproduction of, respectively, constant distances (Tau effect) or constant time intervals (Kappa effect) were observed, while the reverse was not the case. Thus, dimensional interference occurred when the dimension to be ignored was variable. The results are discussed in the light of the distinction between properties of the stabilized mental image and the process of stabilization.

A model of contextual effect on reproduced extents in recall tasks: the issue of the imputed motion hypothesis.

In this article the fundamental question of space and time dependencies in the reproduction of spatial or temporal extents is studied. The functional dependence of spatial responses on the temporal context and the corresponding dependence of temporal responses on spatial context are reported as the tau and kappa effects, respectively. A common explanation suggested that the participant imputes motion to discontinuous displays. Using a mathematical model we explore the imputed velocity hypothesis and provide a globally fit model that addresses the question of sequences modelling. Our model accounts for observed data in the tau experiment. The accuracy of the model is improved introducing a new hypothesis based on small velocity variations. On the other hand, results show that the imputed velocity hypothesis fails to reproduce the kappa effect. This result definitively shows that both effects are not symmetric.

Dynamics of balancing space and time in memory: tau and kappa effects revisited.

In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization.