Five experiments, involving 456 subjects, were conducted to determine the influence of certain stimulus characteristics of the Müller-Lyer figure on the magnitude of this illusion and on the decrement of the illusion which occurs with practice. The results showed that the magnitude of the illusion is directly related to the length of the oblique lines and inversely related to the angle between the obliques and the prominence of the horizontal line. Reducing the angle between the obliques and reducing the prominence of the horizontal line caused the illusion to decrease more rapidly over a series of 100 trials. The final experiment provided evidence consistent with the interpretation that changes in attention may be responsible for the practice decrement. These results are discussed in terms of perceptual learning. / Thesis / Doctor of Philosophy (PhD)

Two experiments were performed to investigate conditions affecting the Müller-Lyer illusion and its decrement with practice. The first experiment was a methodological study concerned with the setting of the variables before adjustment by the subject. The results indicated that the method employed may determine whether a decrement occurs with repeated trials. The evidence suggested the most suitable method to employ in the succeeding experiment. The second experiment was performed to investigate the effects of practice with another illusion figure on the magnitude of illusion on the Müller-Lyer figure. The practice figure was the same as the Müller-Lyer illusion figure except that circles were replaced by the obliques. It was found that the magnitude of the initial illusion is a decreasing monotonic function of the amount of preliminary training. This finding is interpreted as meaning that in pretraining subjects are practiced in disregarding the context (circles) of the horizontal lines of the figure and this transfers positively to the Müller-Lyer task. / Thesis / Master of Arts (MA)

Las enfermedades neurodegenerativas se caracterizan por la pérdida progresiva e irreversible de neuronas, lo cual perjudica seriamente las funciones neurológicas, por lo que es indispen-sable encontrar una solución efectiva a esta problemática. El sistema nervioso es de difícil acceso y de una enorme complejidad. Utilizar modelos que permitan analizar la génesis y la muerte neuronal, resulta clave para comprender la evolu-ción y establecer potenciales tratamientos para las enferme-dades neurodegenerativas. La retina es un excelente sistema para indagar en estos procesos, dado que forma parte del sis-tema nervioso central y presenta una estructura laminar sen-cilla. En la retina, las enfermedades neurodegenerativas que afectan a las neuronas fotorreceptoras - como la Retinitis Pigmentaria o la Degeneración Macular - culminan con la ce-guera de los pacientes afectados. Actualmente se presentan dos posibles estrategias de tratamiento para estas enfermeda-des: la primera busca conocer los mecanismos que conducen a la apoptosis neuronal, de manera de evitarla mediante el uso de factores que promuevan la supervivencia de los fotorreceptores. La segunda propone regenerar las neuronas perdidas durante la enfermedad mediante el uso de stem cells o células madre, las cuales se caracterizan por la auto-reno-vación y multipotencialidad. Las células gliales de Müller(CGM) serían stem cells en la retina. Numerosos trabajos indican que las CGM son capaces de de-diferenciarse y proliferar luego de un daño en la retina, para luego expresar marcadores de fo-torreceptores. Este comportamiento es ampliamente recono-cido en peces y anfibios, sin embargo resulta más restringido en aves y mamíferos. Para poder utilizarlas en el tratamiento de patologías degenerativas, es clave conocer varios aspec-tos de la biología de las CGM como stem cells en animales superiores. Por otra parte, la rápida muerte por apoptosis de las células regeneradas dificulta notablemente el éxito de las terapias de reemplazo. Por lo tanto, es importante dilucidar cómo evitar dicha muerte. Estudios previos de nuestro labora-torio indicaron que las CGM expresaron marcadores de multipo-tencialidad por largos períodos in vitro, y que esta expresión era regulada por la interacción con neuronas de retina o el agregado de factores tróficos. El objetivo del presente trabajo de Tesis fue evaluar el potencial comportamiento como célu-las madre de las CGM de roedores, determinando si eran capa-ces de generar neuronas fotorreceptoras in vitro. Para ello di-señamos tres sistemas de cultivos celulares de retina (neuro-nales puros, gliales puros y cultivos mixtos neuro-gliales) en los cuales analizamos la presencia, origen y evolución de pro-genitores multipotentes, determinando si retenían las caracte-rísticas de multipotencialidad a través de los pasajes. A conti-nuación evaluamos la capacidad de diferenciación de dichos progenitores en fotorreceptores maduros y funcionales; y si el agregado de factores lipídicos podía prevenir la apoptosis de los fotorreceptores regenerados. En el Primer Capítulo evalua-mos si las CGM presentaban dos características de las células madre: la capacidad de expresar marcadores de multipoten-cialidad a través de los pasajes, y de generar progenitores neuronales. Determinamos que tras el repique de cultivos enri-quecidos en CGM, las CGM retuvieron la expresión de Nestina, a la vez que co-existieron con una población de progenitores que bajo condiciones adecuadas se diferenciaron en neuronas La existencia de progenitores en estos cultivos secundarios planteó cuatro preguntas: De dónde provienen los progenito-res? Expresan otros marcadores de multipotencialidad? Es posible diferenciarlos en fotorreceptores? Existen factores que promuevan su supervivencia y/o diferenciación? Antes de avanzar con ellas evaluamos si las dos poblaciones mayorita-rias en cultivos primarios de retina (CGM y neuronas), influían en el destino que los progenitores adoptaban in vitro. Deter-minamos que sólo la interacción de CGM con neuronas de reti-na permitía la generación y/o conservación de progenitores multipotentes por largos períodos en cultivo. En el Segundo Capítulo analizamos el origen y la expresión de marcadores de multipotencialidad en los progenitores observados tras el repi-que. Determinamos que los progenitores expresaron -además de Nestina- Sox-2 y Pax-6 a la vez que conservaron su capa-cidad proliferativa. Estas características se observaron sólo en los pasajes de cultivos mixtos neuro-gliales: los cultivos puros neuronales no sobrevivieron al repique, mientras que los cultivos puros de CGM no generaron progenitores de retina. Los progenitores retuvieron la expresión de Pax-6 y Sox-2 y continuaron proliferando aún luego de cuatro pasajes sucesi-vos de cultivos mixtos. Algunos de ellos, inclusive, expresaron Crx, hecho que indicaba su capacidad de diferenciación en neuronas fotorreceptoras. Para establecer el origen de los pro-genitores de retina en los repiques, utilizamos una sonda fluorescente que nos permitió identificar la progenie tanto de los progenitores como de las CGM. Este análisis sugirió que los progenitores multipotentes observados en los sucesivos repi-ques se originarían en progenitores pre-existentes preserva-dos por la interacción con las CGM y no en las CGM. En el tercer capítulo investigamos la capacidad de diferenciación de los progenitores multipotentes en neuronas fotorreceptoras. Determinamos que en los cultivos mixtos neuro-gliales, bajo condiciones adecuadas de cultivo los progenitores se diferen-ciaron en fotorreceptores maduros y funcionales, que expre-saron marcadores característicos de fotorreceptores (como Crx, Opsina, Periferina) a la vez que fueron capaces de res-ponder a la luz y de capturar glutamato por mecanismos de alta afinidad. Por último, investigamos si era posible bloquear o retrasar el desarrollo de la apoptosis en las células regene-radas. Determinamos que la administración de DHA y S1P - dos moléculas lipídicas con efectos anti-apoptóticos en fo-torreceptores-disminuyeron significativamente la apoptosis neuronal en los repiques. En conclusión, en este trabajo de Tesis establecimos una nueva función para las células gliales de Müller: su capacidad de transformar a las células progeni-toras de retina en células multipotentes, y de promover su diferenciación en neuronas fotorreceptoras. Esta novedosa función podría ser relevante al momento de diseñar nuevas estrategias para el tratamiento de enfermedades neurode-generativas de la retina. / Neurodegenerative diseases are characterized by progressi-ve and irreparable neuronal death, which ends up in major neurological dysfunctions. This scenario has prompted re-searchers to find an effective cure for these diseases; however, few results have been achieved so far. Studying the nervous system is very complicated, because of its difficult access and the vital functions that rely upon it. Thus, having an appropriate model to study neuronal genesis and degeneration is very important in order to find a valid treatment for neurodegenerative diseases. The retina is an excellent model for this type of studies: it is part of the central nervous system, has a very simple structure and is readily accessible. Retinal neurodegene-rative diseases, like Retinitis Pigmentosa (RP) or age- related macular degeneration (AMD), are characterized by extensive photoreceptor loss, which results in visual impairment and/or complete blindness. Two possible strate-gies are now being considered to find a cure for these pa-thologies: one strategy is to avoid neuronal degeneration, by using trophic factors that promote neuronal survival. The second strategy proposes using stem cells to replace the neurons lost during neurodegenerative diseases. Müller glial cells (MGC) are possible candidate to behave as stem cells in the retina. Several studies indicate that, after retinal injury, MGC are capable of de-differentiating and proliferating, and later expressing photoreceptor markers. This regenerative capacity is very robust in lower verte-brates, but much more restricted in birds and mammals.In addition, for stem cells to be useful in the treatment of retinal neurodegenerative diseases, an important issue needs to be solved: the rapid and extensive apoptosis of newly generated neurons. In this regard, it is essential to find molecules able to promote neuronal survival.Pre-vious studies from our laboratory indicate that MGC ex-press stem cell markers for several days in vitro. Moreo-ver, this expression can be regulated by both interactions with retinal neurons and supplementation with trophic factors. The present Doctoral Thesis studied the behavior of MGC as stem cells in rodent retinas, evaluating the ability of MGC to originate photoreceptors in vitro through the generation of multipotent retinal progenitors. We used three different types of retinal cultures (pure neuronal, pure glial and mixed neuro-glial cultures), in which we analyzed the presence, origin and evolution of multipotent retinal progenitors. We evaluated their multi-potentiality in passages of the diverse culture systems and their later ability to differentiate into functional photoreceptors. Finally, we investigated if supplementa-tion with docosahexaenoico acid and sphingosine-1-phospate (two lipid molecules with anti-apoptotic effects in photo-receptors in vitro) could promote the survival of newly regenerated neurons. In the First Chapter, we evaluated if MGC presented at least two of the main stem cell features: multipotentiality preserved through successive re-seedings and the ability to give rise to neuronal progenitors. Our results indicated that MGC retained the expression of stem cell marker Nestin after being re-seeded; in addition,they co-existed with a population of progenitors that also ex-pressed Nestin and, eventually, differentiated into neurons. The presence of neuronal progenitors in these se-condary cultures raised four important questions: Which cells originate these progenitors? Do they express other stem cell markers, besides Nestin? Is it possible to indu-ce their differentiation into photoreceptors? Is there any trophic factor that may promote their survival and/or indu-ce their differentiation into neurons? Before looking for answers to these questions, we evaluated if the two most abundant cells in retinal cultures (MGC and neurons) could influence photoreceptor fate in culture. We determined that progenitors were only able to retain the expression of stem cell marker Nestin for several days in vitro in mixed neuron-glial cultures. In the Second Chapter we ana-lyzed the source and the expression of other stem cell mar-kers in multipotent progenitors present in secondary cultu-res. Our results indicated that progenitors expressed Sox-2 and Pax-6, and preserved the ability to proliferate. The-se characteristics were only found in secondary mixed neuro-glial cultures; re-seeding of pure neuronal cultures led to generalized cell death, while re-seeding of pure glial cultures only generated glial cells, since no proge-nitors where found in this condition. To our surprise, pro-genitors from mixed cultures could be consecutively re-seeded until the fourth passage still preserving the ex-pression of stem cell features while some of them began to express Crx (an early transcription factor for photorecep-tors). To address the question about the source of the pro-genitors in the re-seedings, we used a fluorescent probe that separately labeled the progeny of both MGC and proge-nitors. We determined that multipotent progenitors did not originate from MGC; instead, they derived from pre-exis-tent progenitors present in the donor retina, which were preserved after passages due to their interactions with MGC. In the Third Chapter we investigated the ability of multipotent progenitors to differentiate into photorecep-tors. We determined that in secondary mixed cultures, pro-genitors differentiated into mature photoreceptors that expressed Opsin, Crx and peripherin. Moreover, they displa-yed functional features: they responded to light stimuli and showed high affinity-glutamate uptake, characteristics found in mature photoreceptors in the retina in vivo. Fi-nally, we evaluated if docosahexaenoic acid (DHA) and sphingosine-1-phosphate (S1P) promoted the survival of newly generated neurons. Our results indicated that supple-mentation of secondary mixed cultures with both DHA and S1P significantly reduced the number of apoptotic neurons, suggesting they might be useful in preventing neuronal apoptosis after their regeneration is achieved.We conclude that MGC may have an alternative function in retina regene-ration: besides giving birth to neurons -as many others researchers suggest-, we believe that MGC may help to res-tore neuronal populations by preserving a pool of progeni-tors in a multipotent state, and by later inducing their differentiation into mature and functional photoreceptors.

Cette thèse a été consacrée au développement et à la mise en oeuvre d’un imageur polarimétrique de Müller installé sur un colposcope standard dans le but de diagnostiquer invivo des lésions précancéreuses du col utérin.Ce travail s’est appuyé sur le développement réalisé durant les dix dernières années au LPICM à l'École polytechnique d’une nouvelle technologie d'imagerie médicale non invasive et a priori adaptée à la détection précoce du cancer : l’imagerie polarimétrique. / This thesis was devoted to the development and the implementation of a polarimetric imager of Müller installed on a standard colposcope in order to diagnose invivo precancerous lesions of the cervix.This work was based on the development carried out during the last ten years at the LPICM at the Ecole polytechnique of a new non-invasive medical imaging technology and a priori adapted to the early detection of cancer: polarimetric imaging.

Three experiments were conducted to investigate the two visual systems hypothesis (Milner & Goodale, 1995) and the planning-control hypothesis (Glover, 2002). Experiment 1 required the participants to make rapid aiming movements to 25 cm and 35 cm tails-in, no tails, or tails-out Müller-Lyer stimuli following a 0 ms or 5000 ms no-vision delay. In Experiment 2, the participants executed their movements with full vision of the Müller-Lyer vertices that either remained the same or changed to a different configuration upon movement initiation. Vision was occluded either 350 ms or 450 ms after the onset of the movement. Experiment 3 was similar to Experiment 2, except the amount of visual feedback for on-line control was constrained to 200 ms, 400 ms, or 600 ms. The results of these experiments are problematic for both hypotheses. The participants exhibited a similar pattern of illusion-induced bias in both short and long delay conditions. In addition, the magnitude of the aiming bias increased as the movement unfolded (Experiment 1). Furthermore, even though participants were engaging in on-line control the illusion continued to exert its effects on aiming during the latter stages of the movement (Experiment 2). This effect was also observed when participants had sufficient time to process visual feedback in order to modify their movements (Experiment 3). Taken together, the results suggest that on-line control is biased by visual illusions. / Thesis / Master of Science (MSc)

No description available.

Liszt, the pianist well-known for his outstanding performing style, has led a trend of 19th century virtuoso style and created a phonomonon for piano world in the Romantic period. A great deal of his piano transcriptions have helped to promote many composers¡¦ works and also the development of modern piano manufacture to the new level. Those transcriptions have become the standard concert repertoire of modern virtuoso pianists. A large proportion of Liszt¡¦s piano transcriptions is Schubert Lieder transcriptions which were increasing brilliant style within the beauty and simplicity of Schubert¡¦s melody. The Müllerlieder is the last one of Schubert lieder transcriptions that Liszt composed in 1846. Through his superb compositional technique, this transcription conveys musical content of Schubert lieder successfully. Chapter one in this paper will introduce Liszt¡¦s compositional life of piano transcriptions, including the society background and different types of transcriptions. The connection between Liszt and Schubert lieder is also discussed in it. Chapter two includes the development of piano and the virtuoso style in the times of Liszt. The last chapter focuses on the research of Die Schöne Müller, comparing Schubert¡¦s original song edition and the transcription of Liszt and concentrates on analyzing Liszt¡¦s compositional technique in this piano transcription.

This thesis analyzes three works of the GDR dramatist Heiner Müller: his early prose poem Orpheus gepflügt, his learning play Mauser, and his late piece Verkommenes Ufer Medeamaterial Landschaft mit Argonauten. It demonstrates how Müller, throughout different career stages, pragmatizes myth to further critical thinking. Ancient Greek myths and Christian symbolism play a crucial role in Müller’s strategy of calling into question the very systems that lay claim to an absolute truth. Müller both alludes to and openly employs myths to identify their inherent dialectical tension operative in everyday life as well as in secular explanatory models used to legitimize political agendas. He expands Theodor W. Adorno’s concept of negative dialectics through an emphasis on the mythical pole of the dialectical dyad “myth and enlightenment.” By drawing attention to myths inherent in civilization, Müller opens up space for the imagination and the potential of the irrational to initiate change.

Dissertação (mestrado)—Fundação Universidade de Brasília, Programa de Pós-Graduação em Biologia Animal, 2016. / Submitted by Marianna Gomes (mariannasouza@bce.unb.br) on 2016-12-15T16:02:08Z No. of bitstreams: 1 2016_MarianaElenaJacobsen.pdf: 2780121 bytes, checksum: 7cea0dd11bbebf46eb99cd3c629adf9f (MD5) / Approved for entry into archive by Raquel Viana(raquelviana@bce.unb.br) on 2017-01-30T21:07:23Z (GMT) No. of bitstreams: 1 2016_MarianaElenaJacobsen.pdf: 2780121 bytes, checksum: 7cea0dd11bbebf46eb99cd3c629adf9f (MD5) / Made available in DSpace on 2017-01-30T21:07:23Z (GMT). No. of bitstreams: 1 2016_MarianaElenaJacobsen.pdf: 2780121 bytes, checksum: 7cea0dd11bbebf46eb99cd3c629adf9f (MD5) / A esquizofrenia é um transtorno psiquiátrico altamente debilitante que atinge quase 1% da população mundial e, aproximadamente, a 2 milhões de pessoas no Brasil. É uma doença que apresenta componentes multifatoriais, uma vez que tanto fatores genéticos quanto ambientais já foram associados a ela, embora as causas do aparecimento da enfermidade ainda não estejam esclarecidas. Estudos recentes têm demonstrado que os indivíduos esquizofrênicos apresentam uma sensibilidade alterada nas ilusões visuais como a de Müller-Lyer. Foi demonstrado previamente, mediante uma pesquisa de nosso grupo, que os macacos pregos são também sensíveis a essa ilusão. O objetivo do presente trabalho foi estudar as possíveis alterações na percepção visual dos macacos Sapajus spp. no teste da Ilusão de Müller-Lyer usando uma droga que simula alguns dos sinais próprios da esquizofrenia. Para isso, foi desenvolvido um script no programa E-prime, que permite a implementação do teste e a manipulação dos estímulos visuais. Foram utilizados cinco animais (três fêmeas e dois machos). Os sujeitos foram treinados para escolher a menor entre duas linhas, independentemente do contexto (i.e., da orientação das setas). Posteriormente, foi determinado o Ponto de Igualdade Subjetiva (PIS) sem setas e com setas, para cada um dos animais. Em seguida, os sujeitos foram testados no PIS correspondente ao longo de 12 dias: 4 dias com administração de veículo, 4 dias com administração de MK-801 e 4 dias pós-teste, sem injeções. Os resultados indicam que, depois da administração de MK-801, os sujeitos aumentaram a quantidade de respostas corretas no teste da ilusão em comparação com a administração do veículo e do pós-teste. Esta melhora sugere que o antagonismo de receptores glutamatérgicos NMDA diminui a sensibilidade do macaco-prego à ilusão de Müller-Lyer. Estes resultados, abrem a possibilidade de rastreamento de fármacos antipsicóticos em primatas nãohumanos utilizando o MK-801. / Schizophrenia is a debilitating psychiatric disorder that affects almost 1% of global population and 2 million people in Brazil. This disease has multifactorial features, such as genetic and environmental factors. The causes for appearance of schizophrenia in certain subjects have not been determined yet. Recent studies have established that schizophrenic patients have altered sensibility to visual illusions, such as the Müller-Lyer’s illusion. In a study conducted by our group, it was shown that capuchin monkeys are also sensitive to this visual illusion. The objective of the present work is to study the possible alterations in visual perception in the specie Sapajus spp., using a pharmacological model of schizophrenia and testing the Müller-Lyer’s illusion. To achieve that, a script using the program E-prime was developed to test the illusion and to modify certain parameters of the illusion. Five animals were used (three were females and two were males). First, the animals had to be trained to choose the shorter between the two lines with arrows, regardless of the context (i.e., the orientation of the arrows). Later, the Point of Subjective Equality (PSE) was determined for each animal. Finally, the subjects were tested, using their own previously determined PSE, for twelve days: four days with vehicle injections, four days with MK-801 injections and four days post-test without injections. Results indicate that, after the administration of MK-801, the number of correct choices made by the subjects in the task increased compared to vehicle or post-test trials. This suggests that NMDA glutamatergic receptor antagonism decreases sensitivity to Muller-Lyer’s illusion. These results allow for future screening of anti-psychotic drugs in nonhuman primates.

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Ciências da Saúde, 2006. / Submitted by Larissa Ferreira dos Angelos (ferreirangelos@gmail.com) on 2009-10-17T00:32:25Z No. of bitstreams: 1 2006_Elisa Suganuma.pdf: 2518123 bytes, checksum: 0ea0960ce2aa0432b93fe1d33785bda3 (MD5) / Approved for entry into archive by Tania Milca Carvalho Malheiros(tania@bce.unb.br) on 2009-10-19T13:21:34Z (GMT) No. of bitstreams: 1 2006_Elisa Suganuma.pdf: 2518123 bytes, checksum: 0ea0960ce2aa0432b93fe1d33785bda3 (MD5) / Made available in DSpace on 2009-10-19T13:21:34Z (GMT). No. of bitstreams: 1 2006_Elisa Suganuma.pdf: 2518123 bytes, checksum: 0ea0960ce2aa0432b93fe1d33785bda3 (MD5) Previous issue date: 2006 / As ilusões visuais são formadas devido às diferenças entre a percepção de uma figura e suas características físicas reais. Uma das ilusões geométricas mais estudada e conhecida é a ilusão de Müller-Lyer que consiste no julgamento de dois segmentos de retas paralelas, que apesar de possuírem o de mesmo comprimento são percebidas como se tivessem comprimento diferente. Estes segmentos de reta estão acompanhados de alhetas para fora ou para dentro nas suas extremidades, agindo como indutores que fazem com que estes segmentos de reta sejam percebidos como se tivessem comprimentos diferentes. A investigação da percepção visual ilusória em primatas tem utilizado, em sua maioria, macacos do Velho Mundo. O presente trabalho teve como objetivo investigar a percepção visual frente à ilusão de Müller-Lyer em macacos-prego (Cebus spp.), um primata do Novo Mundo, para o qual não há relatos formais sobre o assunto. Para isso, foi desenvolvido um programa computacional que permite a manipulação de parâmetros que afetam a percepção e a possibilita a investigação de ilusões visuais. Foram utilizados 10 sujeitos adultos (cinco machos e cinco fêmeas). Anteriormente aos testes, eles foram modelados a escolher o maior entre dois segmentos de retas paralelas, independentemente da orientação das alhetas. Além do teste para verificar a suscetibilidade à ilusão (ML), também foi investigado o Ponto de Igualdade Subjetivo (PIS sem alhetas e PIS com alhetas), com o objetivo de verificar a magnitude da ilusão. O resultado do teste ML mostrou que todos os sujeitos escolheram preferencialmente o estímulo com as alhetas para fora, não apresentando diferença entre os gêneros. Os valores encontrados para o PIS sem alhetas foram menores que o PIS com alhetas. Portanto, pode-se dizer que os macacos-prego mostraram-se susceptíveis à ilusão e que a posição das alhetas influenciou na percepção do tamanho do segmento de reta. _________________________________________________________________________________________ ABSTRACT / Visual illusions are formed by the differences between the perception of one figure and its real physical characteristics. The Müller-Lyer illusion is the best known and most studied geometric illusion that consists in the subject’s judgment between two parallel lines with the same size, both associated with outwardpointing arrowheads or inward-pointing arrowheads, acting as inductors that make the lines to be perceived to have different sizes. Old World primates had been used to investigate illusory visual perception. This study aimed to investigate the Müller-Lyer illusion in capuchin monkeys (Cebus spp.), a New World primate not yet investigated for this illusion. A computer program was developed to permit the manipulation of parameters that affect the perception and allow the investigation of visual illusions. Ten adult subjects (5 females and 5 males) were used. Before the tests, they were trained to discriminate between two physically different lines with and without arrowheads. Regarding the Müller-Lyer test (ML) monkeys exhibited a susceptibility to the illusion. In order to determine the degree of the illusion, It was performed the Point of Subjective Equality test (PSE with arrowheads and PSE without arrowheads) which is based on the estimation of the point where the lines were considered equally long for stimuli with and without arrowheads. The results of the ML test have shown that all subjects chose preferentially the line with inward-pointing arrowheads in the Müller-Lyer test, irrespective of gender. The PSE without arrowheads value were inferior than PSE with arrowheads. Thus, it was demonstrated that capuchin monkeys were susceptible to the illusion once the perception of the lines size were influenced by the arrowheads direction.