The discrimination of temporal fine structure in call-like harmonic sounds by birds

Thresholds for discriminating changes in the temporal fine structure of call-like, harmonic sounds were measured in zebra finches (Taeniopygia guttata) and budgerigars (Melopsittacus undulatus). Birds could detect changes in periods as short as 1.225 ms at near 100% accuracy even when spectral and envelope cues were identical, as in time-reversed stimuli. Humans performed poorly on such stimuli, paralleling results from previous studies. Bird thresholds were in the range of those reported in neurophysiological studies of the songbird high vocal center (HVC) to temporally modified conspecific songs. Taken together, these results show that birds can hear differences in temporal fine structure in their natural vocalizations that go beyond human capabilities, but whether these abilities have communicative relevance remains to be seen.     

Melodic and harmonic discrimination following unilateral cerebral excision

Seventy-seven subjects who had undergone unilateral temporal, frontal, or frontotemporal lobectomy for the relief of focal epilepsy as well as a group of 20 normal control subjects were tested in two discrimination tasks, requiring the detection of a single-note change in a pattern of three notes played either successively or simultaneously. Patients with right temporal and right frontotemporal excisions demonstrated a significant deficit in melodic discrimination in comparison to the normal control subjects. Further analysis showed that left-temporal lobectomy including excision of Heschl's gyri (the primary auditory receiving area) led to a significant impairment as well, whereas anterior left temporal-lobe damage did not result in a significant deficit. The results suggest that melodic discrimination depends largely but not exclusively on the right temporal lobe, and that the left Heschl's gyri also seem to be necessary to succeed in this task. In the harmonic task, the differences between the groups did not reach significance, although the two tasks were highly correlated.     

The badness of discrimination

The most blatant forms of discrimination are morally outrageous and very obviously so; but the nature and boundaries of discrimination are more controversial, and it is not clear whether all forms of discrimination are morally bad; nor is it clear why objectionable cases of discrimination are bad. In this paper I address these issues. First, I offer a taxonomy of discrimination. I then argue that discrimination is bad, when it is, because it harms people. Finally, I criticize a rival, disrespect-based account according to which discrimination is bad regardless of whether it causes harm.     

The discrimination of graphical elements

A model is proposed to account for how people discriminate quantities shown in pie charts and divided bar graphs (i.e. which proportion is larger, A or B?). The incremental estimation model assumes that an observer sequentially samples from the available perceptual features in a graph. The relative effectiveness of sampled perceptual features is represented by the spread of probability distributions, in the manner of signal detection theory. The model's predictions were tested in two experiments. Participants took longer with pies than divided bars and longer with non‐aligned than aligned proportions in Experiment 1. In Experiment 2, participants took longer with divided bars than pies when graphs were of unequal size. Generally, graphical formats producing longer response times incurred a greater time penalty when the difference between proportions was reduced. These results were in accordance with the model's predictions. Implications for graphical display design are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

The visual discrimination of bending

The sensitivity of observers to nonrigid bending was evaluated in two experiments. In both experiments, observers were required to discriminate on any given trial which of two bending rods was more elastic. In experiment 1, both rods bent within the same oriented plane, and bent either in a frontoparallel plane or bent in depth. In experiment 2, the two rods within any given trial bent in different, randomly chosen orientations in depth. The results of both experiments revealed that human observers are sensitive to, and can reliably detect, relatively small differences in bending (the average Weber fraction across experiments 1 and 2 was 9.0%). The performance of the human observers was compared to that of models that based their elasticity judgments upon either static projected curvature or mean and maximal projected speed. Despite the fact that all of the observers reported compelling 3-D perceptions of bending in depth, their judgments were both qualitatively and quantitatively consistent with the performance of the models. This similarity suggests that relatively straightforward information about the elasticity of simple bending objects is available in projected retinal images.     

The emotional meaning of harmonic intervals

The present study reexamines the hypothesis that there exist emotional attributions specific to simple musical elements. In Experiment 1, groups of participants, with varying musical expertise, rated the emotional meaning of four natural intervals heard as two harmonic sine waves. In Experiment 2, the higher tone was kept constant at an octave above the low tone used in Experiment 1, while the lower tone was constant. Attributions for each interval were positively correlated from one experimental session to another; despite the intervals differed in terms of their component pitches. Musicians gave the most reliable choices of meaning. In a third experiment, participants rated the emotional meaning of various unfamiliar ethnic melodies with expressions describing the intervals’ meaning based on the results of Experiment 1 and 2. There were distinct profiles of emotional meanings for each melody and these coincided with the meaning of intervals that constituted the surface and deep structure of each melody. The intervallic structures (i.e., the main intervals of the tunes) and respective chords for each melody were also presented aurally and participants’ ratings showed similar emotional profiles for these when compared to those of the melodies themselves.     

The discrimination of brief temporal intervals

The discrimination of brief durations (0.25 to 3.75 sec) defined by the presentation of a visual stimulus was examined. The results indicate that the Weber fraction is invariant over this range of temporal intervals, and that the value of the fraction is about 0.05. The relation of these results to the literature on temporal discriminability was discussed.     

The discrimination of two racial samples

Nineteen different anthropometric measures were obtained on all members of each of two racial groups. A procedure was developed and applied to the data to give maximum differentiation between the groups. The method is applicable wherever we have a large number of independent variables and a dependent variable. In such cases, the conventional methods for determining multiple regression constants are very laborious. An iteration method is presented which is more rapid than any with which the writers are familiar. The method selects in sequence those variables which together yield the largest multiple correlation with the criterion. At each step in the procedure, rapid estimates of the regression weights and the multiple correlation at that point are available.     

The influence of stimulus bandwidth on localization of sound in space

The ability of listeners, deprived of prominent interaural time and intensity cues, to locate noise bands differing in width was investigated. To minimize binaural cues, we placed the sound source at various positions in the median sagittal plane. To eliminate binaural cues, we occluded one ear. The stimuli consisted of broadband noise and bands of noise centered at 8.0 kHz. The width of the latter ranged from 1.0 to 6.0 kHz. The results from seven listeners showed that localization proficiency for sounds in the median sagittal plane decreased with decreases in bandwidth for both binaural and monaural listening conditions. This function was less orderly for monaural localization of horizontally positioned sounds. Another consequence of a reduction in bandwidth was an increasing tendency of listeners to select certain loudspeakers over others as the source of the sound. A previous finding showing that localization of sound in the median sagittal plane is more accurate when listening binaurally rather than monaurally was confirmed.     

The discrimination of dog odours by humans

The domestic dog is able to identify both individual conspecifics, i.e. other dogs, and individual interspecifics, e.g. humans, by smell. Whilst humans can recognise individual members of their own species using olfactory information, it is unknown whether they can identify members of any other species in this manner. We examined the ability of humans to identify individual dogs by smell. Twenty-six dog owners were required to smell two blankets, one impregnated with the odour of their own dog, the other impregnated with the odour of an unfamiliar dog. Participants were required to indicate which of the odours smelt the strongest, which smelt the most pleasant, and which of the odours belonged to their own dog. Most of the participants (88.5%) were able to recognise the odour of their own dog. They showed no significant bias, however, in responding which of the odours they thought smelt the strongest or most pleasant. The results indicate that dogs produce odours that are individually distinctive to their owners, and highlight the fact that humans can recognise members of another species using olfactory cues--an ability presumably acquired without conscious effort.     

The discrimination of cat odours by humans

We explored the ability of humans to identify individual cats by smell. Twenty-five cat owners were required to indicate which of two odours (one belonging to their own cat and one belonging to an unfamiliar cat) smelt the strongest, most pleasant, and which belonged to their own cat. Only thirteen (52%) of the participants were able to recognise the odour of their own cat.