David Souto - Academia.edu (original) (raw)

Papers by David Souto

Transportation Research Part F: Traffic Psychology and Behaviour

Our ability to estimate the duration of sub-second visual events is prone to distortions, which d... more Our ability to estimate the duration of sub-second visual events is prone to distortions, which depend both on sensory and decisional factors. To disambiguate between these two influences, we can look at the alignment between discrimination estimates of duration at the point of subjective equality and confidence estimates when the confidence about decisions is minimal, because observers should be maximally uncertain when two stimuli are perceptually the same. Here, we used this approach to investigate the relationship between the speed of a visual stimulus and its perceived duration. Participants were required to compare two intervals, report which had the longer duration, and then rate their confidence in that judgement. One of the intervals contained a stimulus drifting at a constant speed, whereas the stimulus embedded in the other interval could be stationary, linearly accelerating or decelerating or drifting at the same speed. Discrimination estimates revealed duration compress...

Demonstration of a speed discrimination and time-to-arrival task accompanying paper entitled &quo... more Demonstration of a speed discrimination and time-to-arrival task accompanying paper entitled "Judging vehicle speed and time-to-arrival from the roadside: Eye movements and perception" The Video Demonstration shows a trial in the speed discrimination task. The time-to-arrival task judgements, only the prompt to respond changes to "Which vehicle arrived earlier?".<br>

Ear & Hearing, 2022

Objectives: The purpose of the current study was to investigate the potential of pupillometry to ... more Objectives: The purpose of the current study was to investigate the potential of pupillometry to provide an objective measure of competition between tinnitus and external sounds during a test of auditory short-term memory. Design: Twelve participants with chronic tinnitus and twelve control participants without tinnitus took part in the study. Pretest sessions used an adaptive method to estimate listeners’ frequency discrimination threshold on a test of delayed pitch discrimination for pure tones. Target and probe tones were presented at 72 dB SPL and centered on 750 Hz±2 semitones with an additional jitter of 5 to 20 Hz. Test sessions recorded baseline pupil diameter and task-related pupillary responses (TEPRs) during three blocks of delayed pitch discrimination trials. The difference between target and probe tones was set to the individual’s frequency detection threshold for 80% response-accuracy. Listeners with tinnitus also completed the Tinnitus Handicap Inventory (THI). Linear...

Videos showing the use of a cursor to write words by using a virtual keyboard. The cursor has to ... more Videos showing the use of a cursor to write words by using a virtual keyboard. The cursor has to dwell on a letter box for this letter to be selected (typed). <br>Movie 1 shows a condition in which the participant controls the cursor with gaze (measured with an Eyelink 1000 eyetracker). <br>Movie 2 shows a condition in which the participant controls with cursor with a computer mouse. <br>(Refresh frequency was set at 75Hz for the sake of the recording)

Publications vii 1 Theoretical Introduction 1.1 What is the purpose of eye movements? 1 1.2 Atten... more Publications vii 1 Theoretical Introduction 1.1 What is the purpose of eye movements? 1 1.2 Attention 3 1.2.1 Definitions 1.2.2 Attention in visual space 2.4.5 ECT analysis 66 2.4.6 Analysis of trade-offs 2.4.7 Velocity traces 68 2.5 Discussion 2.5.1 Shared gating and target selection for pursuit and saccades 2.5.2 Conclusion 75

Scientific Reports, 2021

To avoid collisions, pedestrians depend on their ability to perceive and interpret the visual mot... more To avoid collisions, pedestrians depend on their ability to perceive and interpret the visual motion of other road users. Eye movements influence motion perception, yet pedestrians’ gaze behavior has been little investigated. In the present study, we ask whether observers sample visual information differently when making two types of judgements based on the same virtual road-crossing scenario and to which extent spontaneous gaze behavior affects those judgements. Participants performed in succession a speed and a time-to-arrival two-interval discrimination task on the same simple traffic scenario—a car approaching at a constant speed (varying from 10 to 90 km/h) on a single-lane road. On average, observers were able to discriminate vehicle speeds of around 18 km/h and times-to-arrival of 0.7 s. In both tasks, observers placed their gaze closely towards the center of the vehicle’s front plane while pursuing the vehicle. Other areas of the visual scene were sampled infrequently. No di...

Psychonomic Bulletin & Review, 2020

Physical interactions between objects, or between an object and the ground, are amongst the most ... more Physical interactions between objects, or between an object and the ground, are amongst the most biologically relevant for live beings. Prior knowledge of Newtonian physics may play a role in disambiguating an object’s movement as well as foveation by increasing the spatial resolution of the visual input. Observers were shown a virtual 3D scene, representing an ambiguously rotating ball translating on the ground. The ball was perceived as rotating congruently with friction, but only when gaze was located at the point of contact. Inverting or even removing the visual context had little influence on congruent judgements compared with the effect of gaze. Counterintuitively, gaze at the point of contact determines the solution of perceptual ambiguity, but independently of visual context. We suggest this constitutes a frugal strategy, by which the brain infers dynamics locally when faced with a foveated input that is ambiguous.

Computers in Human Behavior, 2021

This is a repository copy of Cognitive plasticity induced by gaze-control technology : gazetyping... more This is a repository copy of Cognitive plasticity induced by gaze-control technology : gazetyping improves performance in the antisaccade task.

Frontiers in Human Neuroscience, 2016

Visual uncertainty may affect saccade adaptation in two complementary ways. First, an ideal adapt... more Visual uncertainty may affect saccade adaptation in two complementary ways. First, an ideal adaptor should take into account the reliability of visual information for determining the amount of correction, predicting that increasing visual uncertainty should decrease adaptation rates. We tested this by comparing observers' direction discrimination and adaptation rates in an intra-saccadic-step paradigm. Second, clearly visible target steps may generate a slower adaptation rate since the error can be attributed to an external cause, instead of an internal change in the visuo-motor mapping that needs to be compensated. We tested this prediction by measuring saccade adaptation to different step sizes. Most remarkably, we found little correlation between estimates of visual uncertainty and adaptation rates and no slower adaptation rates with more visible step sizes. Additionally, we show that for low contrast targets backward steps are perceived as stationary after the saccade, but that adaptation rates are independent of contrast. We suggest that the saccadic system uses different position signals for adapting dysmetric saccades and for generating a trans-saccadic stable visual percept, explaining that saccade adaptation is found to be independent of visual uncertainty.

Frontiers in Human Neuroscience, 2015

Adaptation of saccades can be induced by different error signals, such as retinal position errors... more Adaptation of saccades can be induced by different error signals, such as retinal position errors, prediction errors, or reinforcement learning. Recently, we showed that a shift in the spatial goal of a perceptual task can induce saccadic adaptation, in the absence of a bottom-up position error. Here, we investigated whether this top-down effect is mediated by the visibility of the task-relevant object, by reinforcement due to the feedback about the perceptual judgment or by a target selection mechanism. Participants were asked to discriminate visual stimuli arranged in a vertical compound. To induce adaptation, the discrimination target was presented at eccentric locations in the compound. In the first experiment, we compared adaptation with an easy and difficult discrimination. In the second experiment, we compared adaptation when feedback about the perceptual task was valid and when feedback was provided but was unrelated to performance. In the third experiment, we compared adaptation with instructions to fixate one of the elements in the compound-target selection-to the perceptual task condition-target selection and discrimination. To control for a bottomup stimulus effect, we ran a fourth experiment in which the only instruction was to look at the compound. The saccade amplitude data were fitted by a two-state model distinguishing between an immediate and a gradual error correction process. We replicated our finding that a perceptual task can drive adaptation of saccades. Adaptation showed no effect of feedback reliability, nor an effect of the perceptual task beyond target selection. Adaptation was induced by a top-down signal since it was absent when there was no target selection instruction and no perceptual task. The immediate error correction was larger for the difficult than for the easy condition, suggesting that task difficulty affects mainly voluntary saccade targeting. In addition, the repetition of experiments one week later increased the magnitude of the gradual error correction. The results dissociate two distinct components of adaptation: an immediate and a gradual error correction. We conclude that perceptual-task induced adaptation is most likely due to top-down target selection within a larger object.

Journal of vision, 2015

When an error is injected to saccade endpoints by displacing the target midflight during saccades... more When an error is injected to saccade endpoints by displacing the target midflight during saccades, observers typically adjust their saccade amplitudes on later trials to reduce landing error. Since target displacements are much harder to see during a saccade than during fixation (termed "saccadic suppression of displacement"), it is often assumed that observers are unaware of the manipulation for typical displacement amplitudes. Different conceptions of saccade adaptation predict different effects of target visibility on learning rates. One states that when displacements are less likely to be seen the error is attributed to the motor system instead of the external world and learning should be faster. Another one gives no role to visual error attribution itself, but predicts that learning rates are a function of the uncertainty of the visual error and the uncertainty in the visuomotor mapping. In the latter case learning rates should increase with the visibility of the targ...

Proceedings SCCC'98. 18th International Conference of the Chilean Society of Computer Science (Cat. No.98EX212)

The last few years have seen a renewal of interest in the consideration of dynamic programming in... more The last few years have seen a renewal of interest in the consideration of dynamic programming in compiler technology. This is due to the compactness of the representations, which are turning this paradigm into a common way of dealing with highly redundant computations occurring, for instance, in natural language processing, logic programming or abstract interpretation and related to phenomena such as non-determinism or domain ordering. However, it is not usual to find practical studies about what the real interest of these techniques is, and which approaches are better adapted in each case. We justify the consideration of dynamic programming, both in definite clause and context-free grammar parsing, highlighting the parallelism between the conclusions reached in both cases. We focus on the computational properties, suggesting a simple decision guide for the reader interested in applying this technology.

2008 18th International Conference on Electrical Machines, 2008

Abstract-This paper presents a fast software to compute the Three-Dimensional (3D) leakage field ... more Abstract-This paper presents a fast software to compute the Three-Dimensional (3D) leakage field in Shell type power transformers up to 500 kV. The proposed software, Shell-RNM(3D), is based on the Reluctance Network Method (RNM) and developed in EFACEC Energia. ...

The Analyst, 2015

This paper describes the design, implementation and validation of a sensitive and integral techno... more This paper describes the design, implementation and validation of a sensitive and integral technology solution for endotoxin detection.

Journal of Vision, 2010

Anticipatory pursuit allows accurate eye movement initiation with little delay when the target ha... more Anticipatory pursuit allows accurate eye movement initiation with little delay when the target has a predictable behavior, either in its direction, timing or speed. Anticipatory velocity is less extreme when many target speeds are randomly interleaved within a block, compared to ...