Perception of speed in biological motion : more resistant to interference?

O sistema visual humano é frequentemente referido como altamente preparado para extrair informação relevante de padrões de movimento biológico. Nesse sentido, este estudo analisa o efeito de contraste na percepção de velocidade. Os participantes realizaram o julgamento de velocidade numa situação na qual dois point-light walkers simultâneos foram apresentados com diferentes contrastes relativamente ao fundo e com diferentes velocidades de translação. Na Experiência 1, o movimento de translação biológico canônico foi comparado com o movimento de translação rígido, enquanto na Experiência 2 ele foi comparado com o movimento de translação biológico invertido. O padrão biológico canônico apresenta maior taxa de erro, tempos de reação mais elevados e maior vulnerabilidade ao efeito de contraste na percepção da velocidade do que o padrão rígido. No entanto, não foram encontradas diferenças significativas entre o estímulo canônico e o invertido. A Experiência 3 foi implementada com o objetivo de se controlar o papel das pistas posicionais na tarefa de julgamento de velocidade. Os pontos iniciais e finais da trajetória foram combinados de modo a que os point-light walkers mais rápidos e os mais lentos pudessem terminar o ensaio numa posição relativamente mais avançada ou atrasada. Apesar desta variação, o padrão de resultados foi congruente com as observações das Experiências 1 e 2. Aparentemente, os participantes realizaram julgamentos de velocidade factuais, ao invés do uso de pistas espaciais como uma espécie de referência ou comparação de posicionamento. Dado que a percepção dos padrões biológicos foi mais vulnerável aos efeitos de contraste, mas não foi afetada pela familiaridade, este estudo sugere que a percepção de movimento biológico e rígido poderá obedecer às mesmas regras computacionais, pelo menos em tarefas que envolvam padrões em translação e julgamentos de velocidade.The human visual system is often referred to as being highly prepared to extract meaningful information from biological motion patterns. In the present study, the contrast effect on speed perception was analysed. Participants performed a test of speed judgment in which two simultaneous point-light walkers were animated at different translational speeds and contrasts in relation to the background. Standard translational biological motion was compared to rigid translational motion in Experiment 1 and to inverted biological motion in Experiment 2. Higher error rates, reaction times and greater vulnerability to contrast effects on speed perception were found for translational biological motion when compared to rigid motion. No significant differences were found, however, between standard and inverted stimuli. Experiment 3 was implemented in order to control the role of positional cues in speed judgment. The start and finish points of the trajectory were varied so that the faster and slower point-light walkers could finish the trial at a relatively more advanced or more withdrawn position. In spite of the variation of the start and finish points of the trajectories, the pattern of results was still consistent with the findings of Experiments 1 and 2. Participants seemed to perform factual speed judgments instead of using spatial cues as a form of reference or positional matching. Since the perception of biological patterns was more sensitive to contrast effects and not affected by familiarity, it is suggested that perception of biological and rigid motion may follow the same computational rules, at least for tasks involving translational patterns and speed judgment.Fundação para a Ciência e a Tecnologia (FCT

Uncertainty in estimating time-to-passage revealed by reaction times

Fundação para a Ciência e Tecnologia (FCT

The time to passage of biological and complex motion

A significant part of human interactions occur with other human beings and not only with inanimate objects. It is important in everyday tasks to estimate the time it takes other people to reach (time to contact) or pass us (time to passage). Surprisingly, little is known about judging time to contact or time to passage of biological or other complex motions. In two experiments, rigid and non-rigid (biological, inverted, scrambled, and complex non-biological) motion conditions were compared in a time-to-passage judgment task. Subjects could judge time to passage of point-light-walker displays. However, due to relative and opponent movements of body parts, all articulated patterns conveyed a noisier looming pattern. Non-rigid stimuli were judged as passing sooner than rigid stimuli but reflected more uncertainty in the judgments as revealed by precision judgments and required longer reaction times. Our findings suggested that perceptual judgments for complex motion, including biological patterns, are built on top of the same processing channels that are involved on rigid motion perception. The complexity of the motion pattern (rigid vs. non-rigid) plays a more determinant role than the “biologicity” of the stimulus (biological vs. non-biological), at least concerning time-to-passage judgments.Luso-Spanish Integrated Action funded by the Spanish and Portuguese governmentsFundação para a Ciência e a Tecnologia (FCT

The time to passage of biological and complex motion

A significant part of human interactions occur with other human beings and not only with inanimate objects. It is important in everyday tasks to estimate the time it takes other people to reach (time to contact) or pass us (time to passage). Surprisingly, little is known about judging time to contact or time to passage of biological or other complex motions. In two experiments, rigid and non-rigid (biological, inverted, scrambled, and complex non-biological) motion conditions were compared in a time-to-passage judgment task. Subjects could judge time to passage of point-light-walker displays. However, due to relative and opponent movements of body parts, all articulated patterns conveyed a noisier looming pattern. Non-rigid stimuli were judged as passing sooner than rigid stimuli but reflected more uncertainty in the judgments as revealed by precision judgments and required longer reaction times. Our findings suggested that perceptual judgments for complex motion, including biological patterns, are built on top of the same processing channels that are involved on rigid motion perception. The complexity of the motion pattern (rigid vs. non-rigid) plays a more determinant role than the "biologicity" of the stimulus (biological vs. non-biological), at least concerning time-to-passage judgments

Choosing audio devices on the basis of listeners’ spatial perception: A case study of headphones vs in-earphones

The Earphones and Headphones industry is steadily growing following the emergence of new technological advancements and new applications. New methods to determine listeners’ performance using different types of audio output devices will be in high demand. In this paper we adapt a methodology for evaluation of listeners’ auditory localization accuracy to support the choice between two devices. As a case study, we compare a particular set of in-earphones and headphones. Our goal was to present a method that allowed us to: (1) conclude which audio device provided the most accurate sense of auditory localization; (2) understand the effect of training on task performance; and (3) determine which type of device benefits the most from short sessions of training in auditory localization. Participants had better performances using headphones. Nevertheless, we can reduce the differences between devices if short training sessions are included and the same device is used between training and test.info:eu-repo/semantics/publishedVersio

Time-to-passage estimation on periphery : better for biological motion?

In  previous  studies,  complex  motion  stimuli  were  judged  as  passing  sooner  than  rigid stimuli  but  reflected  more  uncertainty  in  the  judgments  as  revealed  by  precision  loss  and  longer reaction  times.  It  is  known  that  biological  motion  can  be  perceived  in  the  periphery .  In  the everyday  life  people  are  required  to  interact  with  or  to  estimate  motion  variables  of  other  agents located  on  the  periphery ,  at  different  locations  of  the  visual  field.  In  this  study ,  stimuli  were presented  in  different  peripheral  location  (16°,  32°  and  48°).  In  a  time-­to-­passage  (TTP)  task  rigid (RM),  biological  (BM)  and  scrambled  (SM)  motion  conditions  were  compared.  Seven  simulated velocities  were  combined  with  seven  starting  distances,  resulting  in  49  levels  of  TTP:  24 conditions  that  arrived  before  1s  and  24  that  arriving  after  1s.  Subjects  had  to  decide  whether the  point-‐‑light  walker  (PLW)  passed  the  eye  plane  before  or  after  a  reference  time  (1s)  signaled by  a  tone.  Subjects  could  judge  time  to  passage  of  PLW  peripherally  to  an  eccentricity  of  at  least 48o.  Judgments  for  complex  motion  patterns  (BM  and  SM)  showed  an  anticipation  of  the passage  combined  with  a  loss  of  precision  when  compared  with  RM,  at  eccentricity  16o.  The effect  of  eccentricity  on  precision  was  revealed  by  the  increase  of  SD  along  eccentricities  for SM.  The  TTP  judgment  seemed  to  become  less  precise  as  the  stimuli  were  displaced  farther along  the  peripheral  field.  For  BM,  an  improvement  on  precision  was  verified  at  eccentricity  32o, and  a  subsequent  deterioration  just  at  eccentricity  48o.  The  anticipation  of  the  passage  for  BM was  no  longer  found  on  periphery ,  while  the  differences  on  the  precision  between  BM  and  RM vanished.Fundação para a Ciência e a Tecnologia (FCT

Bimodal information increases spontaneous interpersonal synchronization of goal directed upper limb movements

When interacting with each other, people often synchronize spontaneously their movements, e.g. during pendulum swinging, chair rocking[5], walking [4][7], and when executing periodic forearm movements[3].Although the spatiotemporal information that establishes the coupling, leading to synchronization, might be provided by several perceptual systems, the systematic study of different sensory modalities contribution is widely neglected. Considering a) differences in the sensory dominance on the spatial and temporal dimension[5] , b) different cue combination and integration strategies [1][2], and c) that sensory information might provide different aspects of the same event, synchronization should be moderated by the type of sensory modality. Here, 9 naïve participants placed a bottle periodically between two target zones, 40 times, in 12 conditions while sitting in front of a confederate executing the same task. The participant could a) see and hear, b) see , c) hear the confederate, d) or audiovisual information about the movements of the confederate was absent. The couple started in 3 different relative positions (i.e., in-phase, anti-phase, out of phase). A retro-reflective marker was attached to the top of the bottles. Bottle displacement was captured by a motion capture system. We analyzed the variability of the continuous relative phase reflecting the degree of synchronization. Results indicate the emergence of spontaneous synchronization, an increase with bimodal information, and an influence of the initial phase relation on the particular synchronization pattern. Results have theoretical implication for studying cue combination in interpersonal coordination and are consistent with coupled oscillator models.Fundação Bial (Grant 77/12) and Fundação para a Ciência e Tecnologia - FCT: SFRH/BD/8839 6/2012; EXPL/MHC - PCN/0162/2013; FCOMP - 01 - 0124 - FEDER - 022674 and PEst - C/CTM/U10264/2011; FCOMP - 01 - 0124 - FEDER - 037281 and PEst - C/EEI/LA0014/2013. This work was financed by FEDER grants through the Operational Competitiveness Program – COMPET

Desenvolvimento de uma cola biodegradável

Este documento especifica o trabalho realizado no estágio, que decorreu na Colquímica, sediada em Valongo. Este trabalho teve como objetivo colaborar no desenvolvimento de uma cola com características biodegradáveis. O estágio foi orientado pela Engenheira Cristina Frutuoso, no que diz respeito à orientação por parte da Colquímica, e pelo Professor Dr. Gilberto Pinto e Alfredo Crispim, ISEP. O trabalho foi dividido em duas instâncias, sendo a primeira direcionada para a formulação de uma cola com características biodegradáveis e a segunda para a realização do teste de Sturm, um teste de biodegradabilidade capaz de quantificar a quantidade de CO2 produzido pelo processo de biodegradação. Inicialmente foram desenvolvidas e estudadas dez formulações através das variações de resinas e óleo plastificante e estudado o seu comportamento reológico relacionado à variação de viscosidade em função da temperatura. Com base nos resultados obtidos verificou-se que a melhor formulação seria a A8. Estudaram-se as propriedades mecânicas da formulação escolhida e decidiu-se que esta estaria apta a ser usada no fecho de caixas de cartão de produtos ultra congelados assim como no fecho de caixas de cartão de detergentes em pó com peso até 3 Kg. Depois de escolhida a formulação deu-se início ao teste de Sturm, teste meramente orientativo. Durante dezassete dias avaliou-se a quantidade de CO2 produzida durante o processo de biodegradação. Após avaliação dos resultados verificou-se que a taxa de biodegradação para a amostra foi de 0,055 g de CO2. Com a finalidade de confirmar os resultados obtidos no teste de Sturm foi efetuada uma réplica do ensaio, a qual se encontra a decorrer sendo os resultados facultados, posteriormente, à empresa.This thesis specifies the study realized during the internship, held in the company Colquímica, headquartered in Valongo. This study aimed to collaborate in producing an adhesive with biodegradable characteristics. The internship was guided by the engineer Cristina Frutuoso, within Colquímica, and by Professors Dr. Gilberto Alfredo Pinto and Alfredo Crispim, within ISEP. The study was divided in two stages, the first being directed to the development of an adhesive with biodegradable characteristics and the second for the realization of the Sturm test, which is a test of biodegradability able to quantify the amount of CO2 produced in the process of biodegradation. Initially there were ten formulations, which were developed and studied through the variations of resins and plasticizing oil, and their rheological behavior was studied with the variation of viscosity with temperature. Based on the results obtained it was observed that the best formula would be A8. The mechanical properties of the chosen formulation were studied and it was decided that this would be able to be used in the closing of card boxes of ultra-frozen products as well as in the closing of boxes of powdered detergents weighing up to 3 kg. After the selection of the formulation, the Sturm test was initiated only as a guide test. During seventeen days the amount of CO2 produced in the process of biodegradation was evaluated. After evaluating the results obtained, it was observed that the biodegradation rate for the sample was 0,055 g CO2. In order to confirm the results obtained in the Sturm test, it was performed a replica of the trial, which is ongoing being the results provided subsequently to the company

Distance perception in immersive environments: the role of photorealism

Immersive environments (IE) are being increasingly used in order to perform psychophysical experiments. The versatility in terms of stimuli presentation and control and the less time-consuming procedures are their greatest strengths. However, to ensure that IE results can be generalized to real world scenarios we must first provide evidence that performance in IE is quantitatively indistinguishable from performance in real-world. Our goal was to perceptually validate distance perception for CAVE-like IEs. Participants performed a Frontal Matching Distance Task (Durgin & Li, 2011) in three different conditions: real-world scenario (RWS); photorealistic IE (IEPH) and non-photorealistic IE (IENPH). Underestimation of distance was found across all the conditions, with a significant difference between the three conditions (Wilks’ Lambda = .38, F(2,134)= 110.8, p<.01, significant pairwise differences with p<.01). We found a mean error of 2.3 meters for the RWS, 5 meters for the IEPH, and of 6 meters for the IENPH in a pooled data set of 5 participants. Results indicate that while having a photorealistic IE with perspective and stereoscopic depth cues might not be enough to elicit a real-world performance in distance judgment tasks, nevertheless this type of environment minimizes the discrepancy between simulation and real-world when compared with non-photorealistic IEs

Audiovisual integration increases the intentional step synchronization of side-by-side walkers

When people walk side-by-side, they often synchronize their steps. To achieve this, individuals might cross-modally match audiovisual signals from the movements of the partner and kinesthetic, cutaneous, visual and auditory signals from their own movements. Because signals from different sensory systems are processed with noise and asynchronously, the challenge of the CNS is to derive the best estimate based on this conflicting information. This is currently thought to be done by a mechanism operating as a Maximum Likelihood Estimator (MLE). The present work investigated whether audiovisual signals from the partner are integrated according to MLE in order to synchronize steps during walking. Three experiments were conducted in which the sensory cues from a walking partner were virtually simulated. In Experiment 1 seven participants were instructed to synchronize with human-sized Point Light Walkers and/or footstep sounds. Results revealed highest synchronization performance with auditory and audiovisual cues. This was quantified by the time to achieve synchronization and by synchronization variability. However, this auditory dominance effect might have been due to artifacts of the setup. Therefore, in Experiment 2 human-sized virtual mannequins were implemented. Also, audiovisual stimuli were rendered in real-time and thus were synchronous and co-localized. All four participants synchronized best with audiovisual cues. For three of the four participants results point toward their optimal integration consistent with the MLE model. Experiment 3 yielded performance decrements for all three participants when the cues were incongruent. Overall, these findings suggest that individuals might optimally integrate audiovisual cues to synchronize steps during side-by-side walking.info:eu-repo/semantics/publishedVersio