2,395 research outputs found
A reaction time approach to size constancy and visual illusions
No full textPer costanza di grandezza si intende la capacità del sistema visivo di mantenere costante la percezione delle
dimensioni di un oggetto, malgrado le modificazioni dell'immagine retinica con la distanza. In letteratura il
rapporto tra grandezza dello stimolo e tempo di reazione (TR) è ben noto: all'aumentare della grandezza i TR
diminuiscono. Con il presente progetto si è voluto verificare se questo effetto sui TR dipenda dalla
grandezza percepita dagli stimoli oppure dalla grandezza che questi producono sulla retina, manipolando sia
la dimensione degli stimoli, sia la distanza stimolo-soggetto. E' stato ottenuto un TR più rapido per gli
stimoli più grandi rispetto a quelli più piccoli, anche se presentati a distanze diverse in modo tale da
produrre sempre la stessa immagine retinica. Questo effetto può essere attribuito al meccanismo della
costanza di grandezza che ha agito sui TR. Per confermare questo dato sono stati condotti ulteriori
esperimenti in condizioni di riduzione percettiva, dove il ruolo della costanza di grandezza può essere
notevolmente compromesso. Per questo motivo, quando gli indizi necessari alla costanza di grandezza sono
stati rimossi attraverso l'utilizzo di uno spioncino per l'osservazione (pinhole), il TR è stato determinato
esclusivamente dalle dimensioni dell'immagine retinica. Infine, in altri esperimenti sono state utilizzate
illusioni ottiche come quella di Ponzo o di Ebbinghaus per indurre una mispercezione della grandezza. Ancora
una volta, stimoli che per effetto dell'illusione sono stati percepiti come più grandi hanno prodotto TR più
rapidi, nonostante la grandezza retinica fosse sempre la stessa. In conclusione, tutti questi risultati
dimostrano che i TR rispondono alla grandezza percepita dagli stimoli, anzichè quella retinica.Size constancy is a property of the visual perceptural system that can keep relatively constant the perceived
size of an object despite changes of the size of the retinal image with distance. The relationship between
size and reaction time (RT) is well known: RT is faster in response to larger than smaller stimuli. Here i
Wanted to verify whether this effect depends upon retinal or perceived size, by changing both stimulus size
and the observer-object distance. I found that when the size of stimuli positioned at a different distance
was adjusted so as to subtend the same retinal image, the larger stimuli were responded to faster than the
smaller ones. This effect can be attributed to size constancy affecting RT. In keepeing with that, when size
constancy cues were removed by using a pinhole for stimulus viewing, RT reflected stimulus retinal size only.
In further experiments I employed visual illusion, such as Ponzo's and Ebbinghaus' to induce misperception of
size. In accord with the size constancy result, stimuli perceived as larger were responded to faster than
those perceived as smaller, despite retinal size was the same. In sum, all these results demonstrate that
simple RT reflects perceiver rather than retinal stimulus size
Pupil size as a gateway into conscious interpretation of brightness
No full textAlthough retinal illumination is the main determinant of pupil size, evidence indicates that extra-retinal factors, including attention and contextual information, also modulate the pupillary response. For example, stimuli that evoke the idea of brightness (e.g., pictures of the sun) induce pupillary constriction compared to control stimuli of matched luminance. Is conscious appraisal of these stimuli necessary for the pupillary constriction to occur? Participants' pupil diameter was recorded while sun pictures and their phase-scrambled versions were shown to the left eye. A stream of Mondrian patterns was displayed to the right eye to produce continuous flash suppression, which rendered the left-eye stimuli invisible on some trials. Results revealed that when participants were aware of the sun pictures their pupils constricted relative to the control stimuli. This was not the case when the pictures were successfully suppressed from awareness, demonstrating that pupil size is highly sensitive to the contents of consciousness
Is simple reaction time affected by visual illusions?
No full textA number of studies have shown that while perceptual judgment is deceived by pictorial illusions, grasping and other kinds of motor behaviour are not. This is in keeping with the existence of two different cortical systems: a ventral stream subserving vision-for-perception and a dorsal stream subserving vision-for-action. The former is sensitive to illusions, the latter is not. Given this dissociation of functions, one wonders whether simple visuomotor reaction time (RT) follows the ventral or the dorsal rule in perceiving illusory figures. Answering this question might contribute to a better understanding of the different functions of the two systems. We carried out two experiments, one with the Ponzo and the other with the Ebbinghaus-Titchener illusion and found that RT is sensitive to both illusions with faster responses to stimuli appearing illusorily bigger than the others. These results show that motor action is subserved by the ventral system when that action directly reports the presence or onset of a target rather than when that action requires a spatial adjustment that reflects the physical features of the target
Letter from Yosh and Irene [Kuromiya] to Michi Weglyn
No full textA letter from Yosh and Irene [Kuromiya] asking Michi Weglyn for materials to create "a pictorial history of the life of Michi Nishiura Weglyn photos and documents" for the tribute to Michi Weglyn on February 21, 1998.These materials are from box 73 and 74 of the Frank Chin Papers. The Frank Chin Papers contain personal and professional correspondence between Frank Chin and Michi Weglyn relating to particular projects on which either author was working as well as files related to the Day of Remembrance Tribute to Michi Weglyn
The Mindful Christian with Irene Kraegel
No full textOur guest for this episode is Irene Kraegel, the author of The Mindful Christian. We examine how Christian life is enhanced by mindfulness
Visual reaction time and size constancy.
No full textWe carried out six experiments to find out whether simple manual reaction time (RT) to flux-equated visual stimuli of different size is modulated by size constancy or by the retinal angle subtended by the stimuli. We found that RT decreased with the increase in perceived stimulus size rather than retinal angle and that this relationship depended on the use of familiar 3-D-like stimuli and on the availability of other size-constancy cues. Thus, a stereotyped speeded motor response, such as that employed in a simple RT paradigm, is modulated by size constancy, as is the case with perceptual judgments. The present results provide original evidence on the relationship between simple RT and perception
Loewenfeld Table 9-3: Work on the Relations Between Iris Structure and Pupillary Movements
No full textTable 9-3, \u27Work on the relation between iris structure and pupillary movements,\u27 in "The Pupil" by Irene E. Loewenfeld. Includes Year, Author, and Species used in experimentation.Loewenfeld, Irene (1993) \u27Table 9-3: Work on the relations between iris structure and pupillary movements.\u27 The Pupil: Anatomy, Physiology, and Clinical Applications. Vol I. pp 418. Wayne State University Press. Detroit: Mich
Evidence of midline retinal nasotemporal overlap in healthy humans: a model for foveal sparing in hemianopia?
No full textThe existence of midline retinal nasotemporal overlap in humans is controversial. Here we used the Poffenberger paradigm and monocular vision to assess the existence of a midline retinal area projecting to both hemispheres and of a possible differential contribution of the two hemiretinae. When brief visual stimuli were presented at 1 degrees eccentricity they were responded to equally quickly with either hand while at 6 degrees the hand on the same side as the stimulated hemifield was consistently faster than the contralateral hand. This pattern of results is consistent with a nasotemporal overlap at 1 degrees and a complete lateralization at 6 degrees . Both hemiretinae contribute to the overlap area which can be considered as responsible for foveal sparing in hemianopic patients
Irene School District No. 3405
No full textPhotograph - A view of Irene School building, Alberta. ATS 7-65-12-W
Irene Smalls
No full textIrene Smalls leading a music program for her book at the Main Library.
Irene Smalls (1950- ) is an award-winning children's author. Her book "Irene Jennie and the Christmas Masquerade" describes an old holiday custom celebrated along the Cape Fear. Slaves in Wilmington, NC and plantations would dress up in costumes around Christmas and New Year's to parade from house to house. Scholars believe this tradition came with the slaves from their West African roots. The "Jonkonnu" celebration continues in Bermuda, but died out in Wilmington after the Civil War. The tradition was picked up by white youngsters who dressed up for "Koonering" in Wilmington until around World War I
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