John G. Neuhoff

Perceptual bias for rising tones

An approaching sound source creates a pattern of rising intensity that can specify the arrival time of the source. Here we found that listeners reliably overestimated the change in level of rising level tones relative to equivalent falling level tones. In a natural environment this overestimation could provide a selective advantage, because rising intensity can signal movement of the source towards an organism. The bias was stronger at higher levels, suggesting that rising loudness is even more critical when a sound source is either close or loud. These results suggest a privileged status of dynamic rising loudness for harmonic tones and an asymmetry in the neural coding of harmonic dynamic intensity change.

An Adaptive Bias in the Perception of Looming Auditory Motion

Rising acoustic intensity can indicate movement of a sound source toward a listener. Perceptual overestimation of intensity change could provide a selective advantage by indicating that the source is closer than it actually is, providing a better opportunity for the listener to prepare for the sources arrival. In Experiment 1, listeners heard equivalent rising and falling level sounds and indicated whether one demonstrated a greater change in loudness than the other. In 2 subsequent experiments listeners heard equivalent approaching and receding sounds and indicated perceived starting and stopping points of the auditory motion. Results indicate that rising intensity changed in loudness more than equivalent falling intensity, and approaching sounds were perceived as starting and stopping closer than equidistant receding sounds. Both effects were greater for tones than for noise. Evidence is presented that suggests that an asymmetry in the neural coding of egocentric auditory motion is an adaptation that provides advanced warning of looming acoustic sources.

Multisensory Integration of Looming Signals by Rhesus Monkeys

Looming objects produce ecologically important signals that can be perceived in both the visual and auditory domains. Using a preferential looking technique with looming and receding visual and auditory stimuli, we examined the multisensory integration of looming stimuli by rhesus monkeys. We found a strong attentional preference for coincident visual and auditory looming but no analogous preference for coincident stimulus recession. Consistent with previous findings, the effect occurred only with tonal stimuli and not with broadband noise. The results suggest an evolved capacity to integrate multisensory looming objects.

Neural Processing of Auditory Looming in the Human Brain

Acoustic intensity change, along with interaural, spectral, and reverberation information, is an important cue for the perception of auditory motion. Approaching sound sources produce increases in intensity, and receding sound sources produce corresponding decreases. Human listeners typically overestimate increasing compared to equivalent decreasing sound intensity and underestimate the time to contact of approaching sound sources. These characteristics could provide a selective advantage by increasing the margin of safety for response to looming objects. Here, we used dynamic intensity and functional magnetic resonance imaging to examine the neural underpinnings of the perceptual priority for rising intensity. We found that, consistent with activation by horizontal and vertical auditory apparent motion paradigms, rising and falling intensity activated the right temporal plane more than constant intensity. Rising compared to falling intensity activated a distributed neural network subserving space recognition, auditory motion perception, and attention and comprising the superior temporal sulci and the middle temporal gyri, the right temporoparietal junction, the right motor and premotor cortices, the left cerebellar cortex, and a circumscribed region in the midbrain. This anisotropic processing of acoustic intensity change may reflect the salience of rising intensity produced by looming sources in natural environments.

Auditory looming perception in rhesus monkeys

The detection of approaching objects can be crucial to the survival of an organism. The perception of looming has been studied extensively in the visual system, but remains largely unexplored in audition. Here we show a behavioral bias in rhesus monkeys orienting to “looming” sounds. As in humans, the bias occurred for harmonic tones (which can reliably indicate single sources), but not for broadband noise. These response biases to looming sounds are consistent with an evolved neural mechanism that processes approaching objects with priority.

Looming sounds as warning signals: The function of motion cues

Sounds with increasing intensity can act as intrinsic warning cues by signalling that the sound source is approaching. However, intensity change is not always the dominant motion cue to a moving sound, and the effects of simple rising intensity sounds versus sounds with full three dimensional motion cues have not yet been directly compared. Here, we examined skin conductance responses, phasic alertness, and perceptual and explicit emotional ratings in response to approaching and receding sounds characterised either by full motion cues or by intensity change only. We found a stronger approach/recede effect in sounds with full motion cues for skin conductance response amplitude, suggesting sustained mobilisation of resources due to their greater saliency. Otherwise, the approach/recede effect was comparable in sounds with and without full motion cues. Overall, approaching sounds elicited greater skin conductance responses and phasic alertness, and loudness change was estimated higher. Also, they were rated as more unpleasant, potent, arousing and intense, and the probability of such sounds to signal a salient event or threat was rated higher. Several of these effects were modulated by sex. In summary, this study supports the suggestion that intensity change is the dominant motion cue mediating the effects of approaching sound sources, thus clarifying the interpretation of previous studies using such stimuli. Explicit emotional appraisal of such sounds shows a strong directional asymmetry and thus may reflect their implicit warning properties.

Dynamic frequency change influences loudness perception: A central, analytic process

Three experiments showed that dynamic frequency change influenced loudness. Listeners heard tones that had concurrent frequency and intensity change and tracked loudness while ignoring pitch. Dynamic frequency change significantly influenced loudness. A control experiment showed that the effect depended on dynamic change and was opposite that predicted by static equal loudness contours. In a 3rd experiment, listeners heard white noise intensity change in one ear and harmonic frequency change in the other and tracked the loudness of the noise while ignoring the harmonic tone. Findings suggest that the dynamic interaction of pitch and loudness occurs centrally in the auditory system; is an analytic process; has evolved to take advantage of naturally occurring covariation of frequency and intensity; and reflects a shortcoming of traditional static models of loudness perception in a dynamic natural setting.

Influence of anxiety, depression and looming cognitive style on auditory looming perception

Previous studies show that individuals with an anticipatory auditory looming bias over-estimate the closeness of a sound source that approaches them. Our present study bridges cognitive clinical and perception research, and provides evidence that anxiety symptoms and a particular putative cognitive style that creates vulnerability for anxiety (looming cognitive style, or LCS) are related to how people perceive this ecologically fundamental auditory warning signal. The effects of anxiety symptoms on the anticipatory auditory looming effect synergistically depend on the dimension of perceived personal danger assessed by the LCS (physical or social threat). Depression symptoms, in contrast to anxiety symptoms, predict a diminution of the auditory looming bias. Findings broaden our understanding of the links between cognitive-affective states and auditory perception processes and lend further support to past studies providing evidence that the looming cognitive style is related to bias in threat processing.

Reply: Perception of changes in loudness

Neuhoff replies — Canévet and his colleagues suggest that their findings address dynamic loudness change and are inconsistent with my recent discovery of a bias for rising intensity tones. However, the two sets of experiments address fundamentally different questions. Canévet et al. s listeners were asked to make judgements about loudness, whereas my listeners were asked to make judgements about the amount of dynamic change. Essentially, their listeners answered the question “How loud is it now?” by assigning a number to the loudness of a changing intensity sound at various times throughout the stimulus duration. This provided a discrete measure of loudness at various snapshots in time. Listeners in my experiments were specifically asked to ignore the overall loudness of the sounds and to make summary judgements about the amount of loudness change, essentially answering the question “How much did it change in loudness?”.

Overcoming naïve mental models in explaining the Doppler shift: An illusion creates confusion

A perceptual auditory illusion is described that may contribute to students’ misunderstanding of the physical principles of the Doppler shift. The illusion advances the formation of naive mental models about the change in observed frequency that occurs as a sound source passes a stationary observer. Factors that may cause misunderstanding are addressed including the following: (i) the semantic distinctions between physical “frequency” and perceptual “pitch,” (ii) the influence of dynamic loudness on pitch, and (iii) the ambiguity of the word “rise” in describing the wave mechanics of the Doppler shift. Implications for teaching the principles of the Doppler shift include addressing the origin of naive beliefs and using the illusion as a salient and conspicuous example of a breakdown of the correspondence between physics and perception.