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)

A methodological study was performed in order to derive a suitable procedure for the study of the Muller—Lyer illusion in the pigeon. Pigeons were trained to peck at one key when the middle wing in a Muller-Lyer figure was displaced towards one of the outside wings, and at the other key when it was displaced towards the other outside wing. The subjects were then presented with varied settings of the middle wing in order to determine the setting at which they would switch from one key to the other. It was found that, in a two-key situation, the pigeon developed a "preference" for one key over the other and that this tendency, carried over into the testing situation, influenced the "switchover point in a direction determined by the key preference. This evidence enabled the derivation of a more suitable method, which is suggest for use in further research on the Muller-Lyer illusion in the pigeon. / Thesis / Master of Arts (MA)

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.

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.

While various studies have related susceptibility to the Mueller-Lyer illusion to mental health, to developmental maturity, and to self-differentiation, there have been no studies in which susceptibility to the illusion has been related to a wide spectrum of self-concept dimensions. It is one of the purposes of the present study to analyze susceptibility to the Mueller-Lyer illusion as a function of errors in self-perception. To the extent that an individual suffers conflicts with regard to his self-concept, in any of its significant dimensions, it is expected that he will suffer a greater susceptibility to the illusion.

Geometrical optical illusions such as the Muller Lyer illusion and the Ponzo illusion have been widely researched over the past 100+ years, yet researchers have not reached a consensus on why human perception is deceived by these illusions or which illusions are the results of the same effects. In this paper, I study these illusions through the lens of a convolutional neural network. First, I successfully train the network to correctly classify how a human would perceive a particular class of illusion (such as the Muller Lyer illusion), then I test the network’s ability to generalize to illusions that it was not trained on (like the Ponzo illusion). I do not find that these networks generalize effectively. Tests to better understand how the network learns to classify these illusions suggest the networks are checking for image data in specific ‘activation regions’ in order to make classifications rather than analyzing the entire illusions.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Programa de Pós-Graduação em Biologia Animal, 2016. / Submitted by Albânia Cézar de Melo (albania@bce.unb.br) on 2016-05-04T12:37:44Z 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 2016-05-04T18:05:50Z (GMT) No. of bitstreams: 1 2016_MarianaElenaJacobsen.pdf: 2780121 bytes, checksum: 7cea0dd11bbebf46eb99cd3c629adf9f (MD5) / Made available in DSpace on 2016-05-04T18:05:50Z (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 pósteste. 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 não-humanos utilizando o MK-801. _______________________________________________________________________________________________ ABSTRACT / 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.