Cooperative and non-cooperative processes of apparent movement of random-dot cinematograms

In this study, we investigated the cooperative and non-cooperative models of stereopsis on apparent movement of the short-range process using spatial frequency filtered random-dot cinematograms. Our results showed that when spatial frequencies were below 4 cycles/degree, maximum displacement (dmax) was decreasing (linearly) with increasing mean frequencies, but at 4 cycles/degree and above dmax stayed constant. For low frequencies, non-cooperative models such as Marr and Poggio's could explain these findings, but not for frequencies above 4 cycles/degree. However, in a previous study we found that the average cooperative neighbourhood for apparent movement of the short-range process is 15 arc min. This fortuitous agreement on 4 cycles/degree could suggest that dmax being constant at frequencies above 4 cycles is related to a cooperative process.     

Vergence eye movement control and multivalent perception of autostereograms

We introduce a dynamical model for automatic vergence eye movement control. In connection with our dynamical system of binocular model neurons that solves the correspondence problem of stereo-vision, we present a complete model for stereo-vision. Our automatic vergence eye movement control adjusts an image segment, which is of momentary interest to the observer. The adjustment is done in such a way that we only need to define a disparity search range of minimal extension. ecently, a new method of encoding (3D) three-dimenional information in 2D pictures was designed in the form of computer-generated patterns of colored dots. At first glimpse, these so-called autostereograms appear as structured but meaningless patterns. After a certain period of observation, a 3D pattern emerges suddenly in an impressive way. Applying our algorithm to autostereograms, we find a fully satisfactory agreement with the multivalent perception experienced by humans. As in nature, in our model the phase transition between the initial state and the 3D perception state takes place in a very short time. Our algorithm is very robust against noise, and there is no need to interpolate a sparse depth map.     

Effects of adaptation to apparent movement on recovery of structure from motion.

Past work on the recovery of three-dimensional structure from dynamic two-dimensional images has led to inconsistent conclusions regarding the contributions of the short-range and long-range motion processes. In the present experiments, subjects adapted to displays (either four lines or 50 randomly positioned pixels) whose spatiotemporal parameters were chosen to favor either the short-range or long-range process. Adaptation periods were followed by test displays that simulated the rotation of a four-pixel random object about the vertical gamma-axis. The dependent measure was the angle of rotation between successive frames of the rotation display at which percepts of three-dimensional structure broke down. Both the original data and derived measures based on best-fitting polynomials showed small but consistent effects: Compared to control conditions, adaptation to short-range motion reduced the angle at which percepts of structure broke down; adaptation to long-range motion increased them. It is suggested that both low-level (i.e. short-range) and high-level (long-range) processes contribute to the recovery of structure from motion.     

The perception of thermal comfort

26 subjects were exposed either to constant temperature in a water bath or to different air temperatures. A differentiation was made between the comfort temperature and the conscious cutaneous thermal sensation.When thermal sensation of the hand was tested for different internal temperatures it was found that the same superficial (skin) temperature could be agreeable or disagreeable depending on the existing internal temperature. Those skin temperatures which lead to normalization of the internal temperature were agreeable; conversely those skin temperatures which increased deviation of the internal temperature from normal were disagreeable.In man there are two sensory components in thermal perception, one superficial discriminative, and one deep which permits appreciation of agreeable and disagreeable.

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Zusammenfassung 26 Personen wurden entweder konstanter Temperatur im Wasserbad oder verschiedenen Lufttemperaturen exponiert und die Komforttemperatur und das HautwÄrmeempfinden bestimmt. Wenn das WÄrmeempfinden der Hand bei verschiedenen Körperinnentemperaturen bestimmt wurde, ergab sich,dass beider gleichen OberflÄchentemperatur der Unterschied zwischen angenehm und unangenehm von der Körperinnentemperatur abhing. Hauttemperaturen, die zu einer Normalisierung der Körperinnentemperatur führten, waren angenehm; umgekehrt, Hauttemperaturen, die die Abweichung der Körperinnentemperatur vom Normalwert verstÄrkten, waren unangenehm.Beim Menschen gibt es zwei sensorische Komponenten des WÄrmeempfindens, eine scharf unterscheidende oberflÄchliche und eine tiefe,die diesen Unterschied zwischen angenehm und unangenehm bestÄtigt.

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Resume Chez 26 sujets (hommes) on pratique soit des bains agités à température constante, soit des expositions à des ambiances aériennes diverses. Des dissociations sont observées entre l'impression de confort et la sensation thermique cutanée consciente. Des tests de sensation thermique au niveau de la main, pratiqués à différentes températures internes, montrent qu'une mÊme température superficielle peut Être perÇue comme agréable ou désagréable selon le niveau de température interne.Sont agréables les températures superficielles qui tendent à corriger l'écart de température interne, à son niveau normal; inversement sont désagréables les températures superficielles qui tendent à éloigner le température interne de ce niveau. On admet que chez l'homme la perception thermique comporte 2 composantes sensibles: l'une discriminative superficielle, l'autre profonde, affective, qui permet d'apprécier l'agréable et le désagréable.