Fusion of auditory components: effects of the frequency of amplitude modulation

The fusion of two amplitude-modulated (AM) tones presented simultaneously was studied. Subjects were presented with an AM tone (A) followed by a copy of itself (B) which was accompanied by another AM tone (C). In different experiments, the subjects were asked either to rate how clearly they could hear Tone B in the BC mixture or whether Tone B was present or not. The stronger the fusion of Tones B and C, the harder it was to "hear out" Tone B. It was found that fusion was strongest when Tones B and C were modulated at the same rate; segregation curves were obtained for the degree of mismatch of modulation frequency.     

Variation in performance on auditory and visual monitoring tasks as a function of signal and stimulus frequencies

Observers were required to detect double jumps of a diffuse light spot jumping in a circular pattern and more intense noise pulses in a pulse train. Seven groups performed at different combinations of stimulus and signal frequencies, higher signal frequency/stimulus frequency ratios, and lower stimulus frequencies. Stimulus frequency was a more potent determiner of performance than signal frequency, and performance was not invariant within a given signal frequency/stimulus frequency ratio. Correlations of dependent measures were also examined.-Results are discussed with reference to various theories of vigilance behavior.     

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.     

Varying temporal location of a conditioned stimulus in heart rate conditioning ofMacaca mulatta

The several functions that a stimulus can assume were investigated in a Pavlovian conditioning procedure. The subjects were six rhesus monkeys; the response under observation was heart rate. The conditioning began with a temporal separation of zero between a signal and a regularly repeating electric shock; the signal was then moved to a series of earlier locations in the inter-shock interval. After six sessions at each location, two sessions followed in which only the shock was delivered periodically. The findings included: (1) A two-phased conditioned cardiac rate response seen at the first location became more multiphasic and irregular during longer intervals between signal and shock; (2) the location where the conditioned response peaked became increasingly variable as the signal was moved back, but this variability maintained a constant proportion to the signal-shock interval; and, (3) heart rate during a presignal period, and during a comparable period in shock only sessions, was generally deceleratory early in training and acceleratory thereafter. Sessions with the signal showed heart rate in the presignal period to have become acceleratory earlier in training than sessions with shock only. The data pertain to stimulus control over heart rate as a function of: (A) the temporal proximity of a signal to an aversive stimulus; and, (B) the presence or absence of the signal. The use of appropriate response units in cardiac conditioning is also discussed.     

The perceived duration of gratings.

Since visible persistence of grating patterns increases with spatial frequency, it is often inferred that the perceived duration of a grating is also longer at higher spatial frequencies. However, other work has demonstrated that the perceived onset of a grating is also delayed at higher spatial frequencies. Thus it is impossible to infer the subjective duration from the results of visible persistence studies alone. In order to estimate perceived duration in the present study, reaction times (RTs) to grating onsets and offsets were measured for a range of spatial frequencies. The results indicate that although the perceived duration (ie the difference between offset and onset RTs) was consistently longer than the physical duration, the estimates of perceived duration did not vary with changes in spatial frequency. Differences between the present results and earlier findings are interpreted in the context of the different methods used to measure perceived offset.     

Is a common grouping mechanism involved in the phenomena of illusory continuity and stream segregation?

Two auditory phenomena--stream segregation and illusory continuity through a wide-band noise interruption--were studied to determine whether the same principles of perceptual organization applied to both. A cycle was formed of a repeating alternation of two short bursts of narrow-band noise (NBN), one centered at a high frequency (H) and the other at a low frequency (L), with shorter bursts of wide-band noise (WBN) inserted between successive NBNs (H WBN L WBN H WBN...). In some conditions, listeners could hear a single NBN moving up and down behind the WBN bursts, although there was no NBN present with the WBN. Listeners rated the strength of this illusory continuity. Center frequency separation, rate of onsets, and bandwidth of the NBNs were varied. Increases in values of all three variables decreased illusory continuity. Other listeners rated the stream segregation of the H and L bands when successive NBNs were separated either by WBN bursts (as above) or by silences. The same three acoustic variables were manipulated. Increases in all three variables decreased the perception of a single stream. The similar disruptive effects on illusory continuity and on the one-stream percept in the stream segregation task support the idea that both phenomena depend on a common preliminary process of linking together the parts of a sequence that have similar frequencies.     

The role of auditory memory traces in attention to frequency

Three cued signal detection experiments demonstrated a role for auditory memory traces in frequency selectivity. The extent to which the cue predicted the signal frequency affected the size of the advantage for signals at the cue frequency over those at distant frequencies when the cue-signal gap was 10 sec but not when it was 1 sec. Detection of occasional signals presented at uncued frequencies was enhanced when they matched the frequency of cues from recent trials. With "relative" cues, which were usually followed by signals at the musical fifth above the cue frequency, performance on occasional signals at the cue frequency was enhanced relative to other unexpected frequencies. These results suggest that, regardless of the listener's expectations and intentions, the detectability of a signal is enhanced if its frequency matches an existing memory trace. One form of voluntary attention to frequency may involve maintaining traces that would otherwise slowly decay.     

The auditory continuity illusion: a parametric investigation and filter model

A sound that is briefly interrupted by a silent gap is perceived as discontinuous. However, when the gap is filled with noise, the sound may be perceived as continuing through the noise. It has been shown that this continuity illusion depends on the masking of the omitted target sound, but the underlying mechanisms have yet to be quantified thoroughly. In this article, we systematically quantify the relation between perceived continuity and the duration, relative power, or notch width of the interrupting broadband noise for interrupted and noninterrupted amplitude-modulated tones at different frequencies. We fitted the psychometric results in order to estimate the range of the noise parameters that induced auditory grouping. To explain our results within a common theoretical framework, we applied a power spectrum model to thedifferent masking resultsand estimated the critical bandwidth of the auditory filter that may be responsible for the continuity illusion. Our results set constraints on the spectral resolution of the mechanisms underlying the continuity illusion and provide a stimulus set that can be readily applied for neurophysiological studies of its neural correlates.     

Infants' and adults' use of duration and intensity cues in the segmentation of tone patterns

Adults and 8-month-olds were presented with sequences in which every third complex tone was either longer or more intense. Segmentation was measured by comparing the detection of silent gaps inserted into three possible locations in each pattern: Silent gaps inserted at perceived segmentation boundaries are harder to detect than gaps within perceived phrases or groups. A go/no-go conditioned head-turn (hand-raising for adults) procedure was used. In Experiment 1, detection was worse for the gaps following the longer complex tones than for the gaps at the other locations, suggesting that the longer tones marked the ends of perceived groups for both infants and adults. Experiment 2 showed that an increase in intensity did not result in any systematic grouping at either age.     

Infants’ and adults’ use of duration and intensity cues in the segmentation of tone patterns

Adults and 8-month-olds were presented with sequences in which every third complex tone was either longer or more intense. Segmentation was measured by comparing the detection of silent gaps inserted into three possible locations in each pattern: Silent gaps inserted at perceived segmentation boundaries are harder to detect than gaps within perceived phrases or groups. A go/no-go conditioned head-turn (hand-raising for adults) procedure was used. In Experiment 1, detection was worse for the gaps following the longer complex tones than for the gaps at the other locations, suggesting that the longer tones marked the ends of perceived groups for both infants and adults. Experiment 2 showed that an increase in intensity did not result in any systematic grouping at either age.     

Monaural Loudness Adaptation for Middle-Intensity Middle-Frequency Signals: The Importance of Measurement Technique

Using the Simple Adaptation technique (SA) and the Ipsilateral Comparison Paradigm (ICP), the authors studied monaural loudness adaptation to a middle-intensity [60 dB(A)] tone at signal frequencies of 250, 1000, and 4000 Hz in the left and right ears. Adaptation effects were absent when the SA procedure was used. However, they were observed uniformly across all frequency values with the ICP, a result that challenges the assertion in the literature, on the basis of SA measures, that loudness adaptation for middle-intensity signals occurs only at frequencies above 4000 Hz. The ICP features periodic intensity modulations (±10 dB relative to the base signal) to accommodate listeners' needs for referents by which they can gauge subtle changes in the loudness of the adapting tone, a key component that is missing in the SA method. Adaptation effects in this investigation were similar in both ears, supporting the equal susceptibility assumption common in loudness adaptation studies.     

The relationship between skin tone dissatisfaction and sun tanning behaviour

Understanding the factors that contribute to sun exposure is vital for skin cancer prevention. The present study aimed to examine the utility of a new measure for cancer prevention research, the Skin Tone Rating Scale. Australian undergraduate women (N = 156) completed an online questionnaire measuring skin tone dissatisfaction, peer and media norms surrounding tanning, internalisation of a tanned ideal, appearance reasons for tanning, and self‐reported tanning behaviour. The two‐item Skin Tone Rating Scale provided a short and easy‐to‐administer measure of skin tone dissatisfaction that correlated with self‐reported tanning behaviour. The Skin Tone Rating Scale was also moderately related to appearance reasons for tanning and internalisation of a tanned ideal, demonstrating concurrent validity. Socio‐cultural influences (from peers and media) were positively correlated with skin tone dissatisfaction, and this relationship was partially mediated by internalisation of a tanned ideal. Although more research is needed to establish causation, this study provides an important addition to sun tanning literature; it provides a new measure to predict self‐reported tanning behaviour, the Skin Tone Rating Scale, which highlights the importance of appearance concerns in relation to tanning and sun exposure.     

Monaural loudness adaptation for middle-intensity middle-frequency signals: the importance of measurement technique

Using the Simple Adaptation technique (SA) and the Ipsilateral Comparison Paradigm (ICP), the authors studied monaural loudness adaptation to a middle-intensity [60 dB(A)] tone at signal frequencies of 250, 1000, and 4000 Hz in the left and right ears. Adaptation effects were absent when the SA procedure was used. However, they were observed uniformly across all frequency values with the ICP, a result that challenges the assertion in the literature, on the basis of SA measures, that loudness adaptation for middle-intensity signals occurs only at frequencies above 4000 Hz. The ICP features periodic intensity modulations (+/-10 dB relative to the base signal) to accommodate listeners' needs for referents by which they can gauge subtle changes in the loudness of the adapting tone, a key component that is missing in the SA method. Adaptation effects in this investigation were similar in both ears, supporting the equal susceptibility assumption common in loudness adaptation studies.     

Signal recognition and the probability-matching decision rule

In a visual binary recognition task in which three levels of signal strength were presented at each of three levels of signal probability, subjects’ behavior was consistent with the signal detection theory notion that the sensory and the decision processes are independent, but did not support the contention that the decision processes obey a likelihood ratio rule. Instead, the evidence suggests that subjects were attempting to probability-match, adjusting the relative frequencies of their responses to correspond with those of the stimuli. The results are discussed in relation to previous findings, against the background of signal detection theory.     

Infants’ responsiveness to maternal speech and singing

Infants who were 6 months of age were presented with extended audiovisual episodes of their mother's infant-directed speech or singing. Cumulative visual fixation and initial fixation of the mother's image were longer for maternal singing than for maternal speech. Moreover, movement reduction, which may signal intense engagement, accompanied visual fixation more frequently for maternal singing than for maternal speech. The stereotypy and repetitiveness of maternal singing may promote moderate arousal levels, which sustain infant attention, in contrast to the greater variability of speech, which may result in cycles of heightened arousal, gaze aversion, and re-engagement. The regular pulse of music may also enhance emotional coordination between mother and infant.     

Connectives and narrative text: The role of continuity

Connectives are text devices that signal the relation between adjacent sentences. Recently there has been a surge of research interest in the role played by connectives in on-line processing. The present research tested the hypothesis that connectives will impact on-line processing to the extent that they signal a text event that represents a departure from the continuity of the events stated in the text. In Experiment 1, participants generated sentences to follow a stimulus sentence. An additive, causal, or adversative connective (or no connective) was provided to serve as the first word of the participants’ sentence. Results showed that sentences generated in response to additive or causal connectives depicted text events that were continuous with the stimulus text. In contrast, sentences generated in response to adversative connectives depicted discontinuous text events. In Experiments 2 and 3, participants read coherent sentence pairs containing inappropriately placed additive, causal, or adversative connectives. Support for the continuity hypothesis was found when it was shown that adversative connectives led to the greatest amount of processing disruption, as measured by longer reading time on the postconnective sentence (Experiment 2) and lower ratings of coherence (Experiment 3). Future research in this area is discussed.     

Disturbances of rhythm formation in patients with Parkinson's disease: part II. a forced oscillation model

The origin of the characteristic disturbances of rhythm formation in patients with Parkinson's disease (the hastening phenomenon) was discussed, using a second-order system of the periodic response. The input signal was regarded as a pulse series of a Dirac function. The output process of the system had maximal errors of response at input frequencies of f = omega0/n (n = 1, 2, . . .), where omega0 was the intrinsic frequency of the system. Damping coefficient epsilon represented a function of an inhibitor against these maximal errors and the errors diverged to infinity when epsilon = 0. The solution of this forced oscillation system indicated that the intrinsic oscillation of the system has a possibility to be excited at these critical frequencies f = omega/n. Inferred from data on the tapping test, the frequency of an intrinsic oscillation was 5 Hz in the central nervous system, then the critical frequencies were predicted 5/n = 5, 2.5, . . . Hz. On the tapping test the errors of response become maximum around 2.5 and 5 Hz (taps per second), and their peak heights increased from the minimum in well trained normal subjects to the maximum in patients. An inhibitory mechanism against the maximal error would function well, i.e. epsilon greater than 0, in normal subjects but so insufficiently (epsilon leads to 0) in patients that the excited intrinsic oscillation would control their response directly. Thus some patients could no longer maintain a synchronous tapping response at 2.5 Hz or 5 Hz and showed a hastened tapping of 5 6 Hz independent of the signal frequency.     

The effect of spatial frequency content on parameters of eye movements

Two experiments were conducted to examine the influence of the spatial frequency content of natural images on saccadic size and fixation duration. In the first experiment 10 pictures of natural textures were low-pass filtered (0.04-0.76 cycles/deg) and high-pass filtered (1.91-19.56 cycles/deg) and presented with the unfiltered originals in random order, each for 10 s, to 18 participants, with the instruction to inspect them in order to find a suitable name. The participants' eye movements were recorded. It was found that low-pass filtered images resulted in larger saccadic amplitudes compared with high-pass filtered images. A second experiment was conducted with natural stimuli selected for different power spectra which supported the results outlined above. In general, low-spatial frequencies elicit larger saccades associated with shorter fixation durations whereas high-spatial frequencies elicit smaller saccades with longer fixation durations.     

Underwater audiogram of the California sea lion by the conditioned vocalization technique

Conditioning techniques were developed demonstrating that pure tone frequencies under water can exert nearly perfect control over the underwater click vocalizations of the California sea lion (Zalophus californianus). Conditioned vocalizations proved to be a reliable way of obtaining underwater sound detection thresholds in Zalophus at 13 different frequencies, covering a frequency range of 250 to 64,000 Hz. The audiogram generated by these threshold measurements suggests that under water, the range of maximal sensitivity for Zalophus lies between one and 28 kHz with best sensitivity at 16 kHz. Between 28 and 36 kHz there is a loss in sensitivity of 60 dB/octave. However, with relatively intense acoustic signals (> 38 dB re 1 μb underwater), Zalophus will respond to frequencies at least as high as 192 kHz. These results are compared with the underwater hearing of other marine mammals.     

Effects of glide slope, noise intensity, and noise duration on the extrapolation of FM glides through noise.

Listeners are quite adept at maintaining integrated perceptual events in environments that are frequently noisy. Three experiments were conducted to assess the mechanisms by which listeners maintain continuity for upward sinusoidal glides that are interrupted by a period of broadband noise. The first two experiments used stimulus complexes consisting of three parts: prenoise glide, broadband noise interval, and postnoise glide. For a given prenoise glide and noise interval, the subject's task was to adjust the onset frequency of a same-slope postnoise glide so that, together with the prenoise glide and noise, the complex sounded as "smooth and continuous as possible." The slope of the glides (1.67, 3.33, 5, and 6.67 Bark/sec) as well as the duration (50, 200, and 350 msec) and relative level of the interrupting noise (0, -6, and -12 dB S/N) were varied. For all but the shallowest glides, subjects consistently adjusted the offset portion of the glide to frequencies lower than predicted by accurate interpolation of the prenoise portion. Curiously, for the shallowest glides, subjects consistently selected postnoise glide onset-frequency values higher than predicted by accurate extrapolation of the prenoise glide. There was no effect of noise level on subjects' adjustments in the first two experiments. The third experiment used a signal detection task to measure the phenomenal experience of continuity through the noise. Frequency glides were either present or absent during the noise for stimuli like those use in the first two experiments as well as for stimuli that had no prenoise or postnoise glides. Subjects were more likely to report the presence of glides in the noise when none occurred (false positives) when noise was shorter or of greater relative level and when glides were present adjacent to the noise.