Visual Pointers Research Articles

Use of Realism as Social Commentary on Specific Subject Matter in Painting: An Analysis of the Realist Paintings of Zephania Lukamba, Kenyatta University, Nairobi, Kenya

The creation of any work of art often has a purpose or an intent. In this regard, artists endeavour to create pieces of artwork that bear or propagate certain meanings or points of view and also express some social phenomena that are unique to a particular environment or what has often been referred to as a catchment area. This is usually an important artistic undertaking because artists have the innate responsibility to observe certain social peculiarities and visually record them for all their worth. Some of these peculiarities are a reflection of society and its circumstantial behavioural tendencies often brought about by various factors; such as social-economic malaise and bad governance that precipitates social decay. When an artist embarks on such an artistic depiction of his or her own social environment, then there is a need to give it due artistic attention. This study featured 22 paintings based on the subject matter of the overloading of vehicles. Although the paintings appeared generally alike in terms of layout and execution, it is the depiction of the paradox of the repeated occurrence of the same phenomenon which in reality reflects a tendency that is both widespread and bizarre. In this regard, each painting depicts a scene that in reality is in itself a specific curious occurrence. This, in retrospect, can be seen as a type of popular culture of defiance and of the absurd. Since the overloading of any vehicle is ordinarily not only unwarranted and dangerous, but also blatantly illegal, the artist, in his observations which constituted this study, depicts a societal problem that has degenerated into impunity. This study, therefore, sought to find out how effective such focused paintings were as an avenue for social commentary. The artist over a period of time observed incidents of overloading as they manifested themselves in real-life occurrences and made the necessary sketches that were later developed into paintings in the studio. The paintings were examined using formal analysis to delve into their composition and use of elements and principles as well as descriptive analysis to explore their meaning or what the artist intended to convey. The study posits that the essence of such focused paintings in this study is that they become a visual pointer to the wider debate about the debilitating effect of such social malaise upon the psyche of society. The ordinary citizenry subsequently becomes spectators in their own space that degenerates into such recklessness and disregard for individual and collective safety as well as the rule of law

Extent of lateralization of click trains elicited by interaural time differences—A comparison of measurement paradigms

Extent of lateralization measurements have previously been performed for various stimulus types, mainly using two measurement paradigms: (1) an acoustic pointer paradigm where the interaural level difference of a pointer stimulus is adjusted to match the intracranial position of a target stimulus and (2) a visual pointer paradigm where the intracranial position of a target stimulus is indicated on a linear scale. Both measurement paradigms are widely used, but rarely within the same study. In this study, the extent of lateralization elicited by unfiltered as well as 4 kHz bandpass-filtered click trains carrying interaural time differences (ITDs) up to 3 ms was measured using an acoustic as well as a visual pointer paradigm. Data from six young normal-hearing listeners were compared. Using the visual pointer paradigm, the extent of lateralization behavior as a function of stimulus ITD for unfiltered as well as bandpass filtered click trains coincided. The extent of lateralization as determined by the acous...

The interaction of vision and audition in two-dimensional space.

Using a mouse-driven visual pointer, 10 participants made repeated open-loop egocentric localizations of memorized visual, auditory, and combined visual-auditory targets projected randomly across the two-dimensional frontal field (2D). The results are reported in terms of variable error, constant error and local distortion. The results confirmed that auditory and visual maps of the egocentric space differ in their precision (variable error) and accuracy (constant error), both from one another and as a function of eccentricity and direction within a given modality. These differences were used, in turn, to make predictions about the precision and accuracy within which spatially and temporally congruent bimodal visual-auditory targets are localized. Overall, the improvement in precision for bimodal relative to the best unimodal target revealed the presence of optimal integration well-predicted by the Maximum Likelihood Estimation (MLE) model. Conversely, the hypothesis that accuracy in localizing the bimodal visual-auditory targets would represent a compromise between auditory and visual performance in favor of the most precise modality was rejected. Instead, the bimodal accuracy was found to be equivalent to or to exceed that of the best unimodal condition. Finally, we described how the different types of errors could be used to identify properties of the internal representations and coordinate transformations within the central nervous system (CNS). The results provide some insight into the structure of the underlying sensorimotor processes employed by the brain and confirm the usefulness of capitalizing on naturally occurring differences between vision and audition to better understand their interaction and their contribution to multimodal perception.

A test battery to assess localization ability in simulated complex acoustic environments.

In complex acoustic environments, following a target sound is made difficult by the presence of noise and reverberation and especially hearing impaired people struggle understanding speech in such settings. Localizing the speaker is important in such situations to follow discussions and to gain additional benefit from visual cues. A test battery is proposed to quantify localization performance in different realistic environments and with laboratory tests when noise and reverberation are present. The aim is to relate real‐life performance to that in simplified tests. In the localization tests, participants indicate the sound location with a visual pointer. Sounds are played in an anechoic chamber from loudspeakers across the frontal hemi‐field. Localization performance is measured in quiet, in diffuse background noise, and with reverberation of simulated rooms. The ability to cope with a single reflection is assessed in a precedence effect paradigm where participants localize a sound and its delayed copy for various delays and levels. The test battery is completed by questionnaires (e.g., SSQ), a speech, and a cognitive test. By cross‐comparing results from the tests, we attempt to predict the performance in real‐world environments from outcomes of simplified tests particularly in the presence of hearing impairment.

Knowledge maps and organisations: an overview and interpretation

The 'knowledge map' is a relatively new Knowledge Management (KM) tool. Yet the applications of knowledge maps in the organisational context have been insufficiently developed. This paper conducts a critical literature review and offers an alternative view on the necessity of this KM initiative within an organisation. First, the knowledge map's 'duo-functional' feature (displaying knowledge and also serving as visual pointers to knowledge containers) makes it an effective tool for managing different types of knowledge. Second, the advantages of different types of knowledge maps illustrate the strengths of such a KM tool at different KM dimensions. This paper also summarises two main weaknesses in prior knowledge-mapping projects: (1) lack of effective quality control of knowledge maps; (2) immature perceptions of the knowledge-mapping process. A dynamic knowledge map system is proposed in this paper as a feasible model of applying knowledge maps within organisations.

Sensitivity to Interaural Level and Envelope Time Differences of Two Bilateral Cochlear Implant Listeners Using Clinical Sound Processors

To assess the sensitivity of two bilateral cochlear implant users to interaural level and time differences (ILDs and ITDs) for various signals presented through the auxiliary inputs of clinical sound processors that discard fine timing information and only preserve envelope cues. In a lateralization discrimination experiment, the just noticeable difference (JND) for ILDs and envelope ITDs was measured by means of an adaptive 2-AFC method. Different stimuli were used, including click trains at varying repetition rates, a speech fragment, and noise bursts. For one cochlear implant listener and one stimulus, the sensitivity to envelope ITDs was also determined with the method of constant stimuli. The dependency of ILD-JNDs on the interaural place difference was studied with stimulation at single electrode pairs by using sinusoidal input signals in combination with appropriate single-channel processor fittings. In a lateralization position experiment, subjects were required to use a visual pointer on a computer screen to indicate in-the-head positions for blocks of stimuli containing either ILD or ITD cues. All stimuli were loudness balanced (before applying ILD) and fed directly into the auxiliary inputs of the BTE processors (TEMPO+, Med-El Corp.). The automatic gain control and the processors' microphones were deactivated. Both cochlear implant listeners were highly sensitive to ILDs in all broadband stimuli used; JNDs approached those of normal-hearing listeners. Pitch-matched single electrode pairs showed significantly lower ILD-JNDs than pitch-mismatched electrode pairs. Envelope ITD-JNDs of cochlear implant listeners obtained with the adaptive method were substantially higher and showed a higher test-retest variability than waveform ITD-JNDs of normal-hearing control listeners and envelope ITD-JNDs of normal-hearing listeners reported in the literature for comparable signals. The envelope ITD-JNDs for the click trains were significantly lower than for the speech token or the noise bursts. The best envelope ITD-JND measured was ca. 250 mus for the click train at 100 cycles per sec. Direct measurement of the psychometric function for envelope ITD by the method of constant stimuli showed discrimination above chance level down to 150 micros. The lateralization position experiment showed that both ILDs and envelope ITDs can lead to monotonic changes in lateral percept. The two cochlear implant users tested showed strong effects of ILDs in various broadband stimuli with respect to JNDs as well as lateralization position. The high dependency of ILD-JNDs on the interaural pitch difference suggests the potential importance of pitch-matched assignment of electrodes in the two ears by the speech processors. Envelope ITDs appear to be more ambiguous cues than ILDs, as reflected by the higher and more variable JNDs compared with normal-hearing listeners. The envelope ITD-JNDs of cochlear implant listeners depended on the stimulus.

Localization interference between free-field signals

With headphones, the perceived lateral position of one frequency band (the target) can be affected by the presence of a second band with different interaural parameters (the interferer). This binaural interference persists despite a stimulus onset asynchrony (SOA) from interferer to target of up to 320 ms [L. R. Bernstein and C. Trahiotis, J. Acoust. Soc. Am. 94, 735–742 (1993)]. The current study presented targets and interferers in anechoic space from pairs of speakers chosen from an array of 12. A visual pointer was used to indicate the perceived location of the target. Localization of a sinusoidally amplitude-modulated (SAM) target (carrier = 500 Hz, modulator = 250 Hz) was unaffected by the presence of an SAM interferer (carrier = 4000 Hz). When the target was the higher frequency, however, there were large individual differences, with some listeners showing interference while others did not. Unlike the studies with headphones, when interference was seen a distractor to target SOA of only 40 ms was sufficient to eliminate the interference. [Work supported by a grant from the NIH, NIDCD 00087.]

Lateralization of nonspeech audio‐visual stimulus combinations.

Ability to lateralize stimuli was measured in eight normally hearing subjects. In experiment 1 auditory or visual stimuli were presented. Subjects responded with an auditory or visual pointer in conditions where stimulus and response modalities were the same (uni‐modal) or different (cross‐modal). A linear relationship was found between the position of the target stimuli and the perceived lateral position, establishing the correspondence between auditorily and visually presented positions, consistent with Yost [J. Acoust. Soc. Am. 70, 397–409 (1981)]. Mean judgments of linear position were independent of stimulus or response modality. In experiment 2 subjects were presented with bi‐modal audio‐visual stimuli with spatially and temporally correspondent modal components and subjects responded with an auditory pointer. Mean judgments of position were similar to those in experiment 1 but standard deviations were significantly smaller for the bi‐modal stimuli relative to uni‐modal stimuli. Experiments 3 and 4 involved manipulations of the spatial or temporal relationship between modal components of bi‐modal stimuli. Whereas the relative importance of the visual modality was confirmed [Colavita, Percept. Psychophys. 15(2), 409–412 (1974)] the results of both experiments indicated that perception of the location of an audio‐visual stimulus is influenced by information conveyed in both modalities. [Work supported by UKBBSRC.]