The perceived pitch and loudness of sounds change as they fuse with reflections from nearby objects. Blind people use both sources of information, with dominance for the use of pitch. We studied if their better performance as compared to sighted can be related to the ability to discriminate tone frequency, repetition pitch and loudness. Only loudness discrimination differed between blind and sighted persons.

The Google search engine was studied as a Web prototype to be modified and improved for blind users. A Specialized Search Engine for the Blind (SSEB) was developed with an accessible interface and improved functions (searching assistance functions, user-centered functions, and specialized design for the blind). An experiment was conducted with twelve participants, both blind and sighted, to verify the effects of SSEB. The performance was better with the SSEB than with the Google search engine, and the participants also showed higher satisfactions with the SSEB. Interface considerations for designing an accessible Web site for blind users are important. The users of SSEB could in the future be expanded to include most, if not all, visually impaired people, since the World Wide Web and all Internet resources should ideally be accessible to everyone.

Change blindness on web pages was studied for 20 participants. The purpose was to find how change blindness appears for web pages, and which changes are easier to detect. The task was to detect if a change had occurred and to show this by the means of the cursor. Rensink's flicker paradigm was used, where four categories of changes were presented. It was easier to detect a change not consisting of a person than one with a person. It was easier to detect a change to the left than to the right. The complexity of the web pages did not appear to have an effect, while large changes were easier to detect than small. The results may indicate that focused attention is differently sensitive for different kinds of changes. They also show that change blindness is a general phenomenon that can be applied to the perception of web pages.

Change blindness on web pages was studied for 20 participants. The purpose was to find how change blindness appears for web pages, and which changes are easier to detect. The task was to detect if a change had occurred and to show this by the means of the cursor. Rensink´s flicker paradigm was used, where four categories of changes were presented. It was easier to detect a change not consisting of a person than one with a person. It was easier to detect a change to the left than to the right. The complexity of the web pages did not appear to have an effect, while large changes were easier to detect than small. The results may indicate that focused attention is differently sensitive for different kinds of changes. They also show that change blindness is a general phenomenon that can be applied to the perception of web pages.

Color interaction is a perceptual effect that will influence how color combinations appear to an observer. Two main categories are color induction and color assimilation, the former when two colors become more different looking, and the latter when two colors become more similar looking. Typical examples are presentations of web pages on computer displays, cartographic pictures and maps, artistic displays such as paintings, and of environmental images, such as colors on houses. In this survey of concepts and research, the focus is on fundamental issues and definitions regarding these effects. The emphasis is on modern types of displays and relevant characteristics of different technologies are also given. Some historic perspectives are included. Different color appearance models and how they take color interaction into consideration are discussed, also including information on suitable possible color adjustments that the models may give. References are made to modern visual perceptual theories, and the place of these effects in a broader perceptual theory is considered. A number of illusions and pictures that illustrate interaction effects are included. As an example an experiment with perceived interactions between geometrical objects is described in short. Six observation colors and three interaction colors for each observed color were presented to ten observers, who performed a matching task. The result of this study is presented as color interaction diagrams in the CIELUV color space. The importance of color and color interaction in different applications is discussed together with a set of guidelines. The advantages and disadvantages that may result from using the guidelines are addressed. Some concluding remarks on possible future work in color interaction are given.

Blind persons emit sounds to detect objects by echolocation. Both perceived pitch and perceived loudness of the emitted sound change as they fuse with the reflections from nearby objects. Blind persons generally are better than sighted at echolocation, but it is unclear whether this superiority is related to detection of pitch, loudness, or both. We measured the ability of twelve blind and twenty-five sighted listeners to determine which of two sounds, 500 ms noise bursts, that had been recorded in the presence of a reflecting object in a room with reflecting walls using an artificial head. The sound pairs were original recordings differing in both pitch and loudness, or manipulated recordings with either the pitch or the loudness information removed. Observers responded using a 2AFC method with verbal feedback. For both blind and sighted listeners the performance declined more with the pitch information removed than with the loudness information removed. In addition, the blind performed clearly better than the sighted as long as the pitch information was present, but not when it was removed. Taken together, these results show that the ability to detect pitch is a main factor underlying high performance in human echolocation.

Blind people may detect objects from the information in reflected sounds, echolocation. Detection as a function of the number of clicks compared to a continuous noise was tested by presenting clicks of 5 ms with rates from 1 to 64 clicks during a 500 ms period and a 500-ms continuous white noise. The sounds were recorded in an ordinary room through an artificial binaural head. The reflecting object was an aluminum disk, diameter 0.5 m, at distances of 1 and 1.5 m. These sounds were later presented to 3 blind and 16 sighted participants in a laboratory using a 2AFC methodology. The task was to detect which of the two sounds that contained a reflecting object. Feedback was provided. The blind participants had a higher detection than the sighted, but there were also differences among the blind. These results are put in relation to physical features such as the autocorrelation function and spectral variations.

Research suggests that blind people are superior to sighted in echolocation, but systematic psychoacoustic studies on environmental conditions such as distance to objects, signal duration, and reverberation are lacking. Therefore, two experiments were conducted. Noise bursts of 5, 50, or 500 ms were reproduced by a loudspeaker on an artificial manikin in an ordinary room and in an anechoic chamber. The manikin recorded the sounds binaurally in the presence and absence of a reflecting 1.5-mm thick aluminium disk, 0.5 in in diameter, placed in front, at distances of 0.5 to 5 m. These recordings were later presented to ten visually handicapped and ten sighted people, 30 62 years old, using a 2AFC paradigm with feedback. The task was to detect which of two sounds that contained the reflecting object. The blind performed better than the sighted participants. All performed well with the object at < 2 in distance. Detection increased with longer signal durations. Performance was slightly better in the ordinary room than in the anechoic chamber. A supplementary experiment on the two best blind persons showed that their superior performance at distances > 2 m was not by chance. Detection thresholds showed that blind participants could detect the object at longer distances in the conference room than in the anechoic chamber, when using the longer-duration sounds and also as compared to the sighted people. Audiometric tests suggest that equal hearing in both ears is important for echolocation. Possible echolocation mechanisms are discussed.

A number of studies have pointed out the resistance to statistics courses and the anxiety it induces among social science students. The attitudes to statistics among psychology and education science students in a new university in Sweden were studied. Seven students were from a higher level course eight were from a course at a second year level. The students were asked voluntarily to respond to a questionnaire. The higher level students were given the questionnaire both before and after the course and they were also interviewed for about one hour each. Although all students experienced anxiety about statistics, some of them had become more positive to statistics after the course. This shows that feelings of interest and anxiety can exist at the same time. The anxiety might often be a result of low self perception of one’s own mathematical abilities. This self-perception must be made more positive. Teaching statistics at the same time to both distance and campus students is not to be recommended. The students expressed a wish for a more continuous teaching of statistics, repetitions, more practical examples and practice in using statistical packages.