Colour matching of isoluminant samples and backgrounds: a dimming effect

Chromatic fading following complete adaptation to unique hues

Profound vision loss occurs after prolonged exposure to an unchanging featureless visual environment. The effect is sometimes called visual fade. Here we investigate this phenomenon in the color domain using two different experiments. In the first experiment we determine the time needed for a colored background to appear achromatic. Four backgrounds were tested. Each represented the observers’ four unique hues. This adaptation time was compared with time to recover after adaptation Hue shifts at the end of the adaptation period were also measured. There were wide individual differences in adaptation times and recovery times. Overall recovery was faster than adaptation (p < 0.02). There were minimal shifts in hue. In the second experiment the changes in saturation (Munsell chroma) and lightness (Munsell value) of the background were monitored at six time intervals during the adapting process. Again asymmetric matching with Munsell samples was used. There were two distinct components to both the adaptation and recovery phases; one fast with time constant <1s, the other slow with time constant between 40 and 160s.

The experiments show that the special case of visual fade involving color represents the sensory basis for many color-related effects involving adaptation.

The History of Lithuanian Psychology

The history of Lithuanian psychology parallels the sociopolitical history of the country. Due to repeated occupations of the country and other unfavorable conditions, scientific thought and innovations were delayed for decades. Development of psychology in Lithuania can be divided in three periods: (1) interwar (1918–1940), (2) Soviet occupation (1940–1990), and (3) regained independence (since 1990). Institutionalization of psychology is analyzed in four aspects: research, development of studies, applied practice, and scientific communication. The beginning of the professional psychology in Lithuania is inseparable from the establishment and activity of the University of Lithuania (later Vytautas Magnus University). Major tasks and activities that the first Lithuanian psychologists undertook during the interwar period were the dissemination of scientific psychological knowledge. Scientific research was consistent with the tendencies established in European psychology, in particular German psychology. During the Soviet period one of the positive facts was an increasing number of professional psychologists due to the renewal of studies (including doctoral studies) in psychology at Vilnius University. However, Lithuania never had state-supported institutions for scientific research in psychology. Due to the restoration of independence in 1990, more educational establishments (at present five universities) provide instruction for psychologists, new curricula of studies are being launched according to the internationally confirmed standard, the relationship of psychology with various practical fields is strengthening, and numerous institutions offer a wide variety of psychological services.

Cone contrasts do not predict color constancy

A successive, asymmetric color-matching paradigm was used to investigate the link between cone contrast and the stability of perceived colors. We measured the perceived color shifts of 10 Munsell samples, induced by test illuminant A, simulated in u'v' color space. The capacity of the visual system to resist these shifts, otherwise known as color constancy, is measured in terms of the Brunswik ratio, BR. Cone contrasts are calculated with respect to either the physical or perceived background. Subjective cone contrasts show a better fit to the von Kries law than those based on the physical background. Complete cone adaptation occurs when color constancy is high. However we show conditions where cone adaptation seems complete but color constancy is poor.