Samuele Carcagno

Is gaze following purely reflexive or goal-directed instead? Revisiting the automaticity of orienting attention by gaze cues

Distracting gaze has been shown to elicit automatic gaze following. However, it is still debated whether the effects of perceived gaze are a simple automatic spatial orienting response or are instead sensitive to the context (i.e. goals and task demands). In three experiments, we investigated the conditions under which gaze following occurs. Participants were instructed to saccade towards one of two lateral targets. A face distracter, always present in the background, could gaze towards: (a) a task-relevant target––(“matching” goal-directed gaze shift)––congruent or incongruent with the instructed direction, (b) a task-irrelevant target, orthogonal to the one instructed (“non-matching” goal-directed gaze shift), or (c) an empty spatial location (no-goal-directed gaze shift). Eye movement recordings showed faster saccadic latencies in correct trials in congruent conditions especially when the distracting gaze shift occurred before the instruction to make a saccade. Interestingly, while participants made a higher proportion of gaze-following errors (i.e. errors in the direction of the distracting gaze) in the incongruent conditions when the distracter’s gaze shift preceded the instruction onset indicating an automatic gaze following, they never followed the distracting gaze when it was directed towards an empty location or a stimulus that was never the target. Taken together, these findings suggest that gaze following is likely to be a product of both automatic and goal-driven orienting mechanisms.

A further test of the linearity of temporal summation in forward masking

An experiment tested the hypothesis that the masking effects of two nonoverlapping forward maskers are summed linearly over time. First, the levels of individual noise maskers required to mask a brief 4-kHz signal presented at 10-, 20-, 30-, or 40-dB sensation level (SL) were found. The hypothesis predicts that a combination of the first masker presented at the level required to mask the 10-dB SL signal and the second masker presented at the level required to mask the 20-dB SL signal, should produce the same amount of masking as the converse situation (i.e., the first masker presented at the level required to mask the 20-dB SL signal and the second masker presented at the level required to mask the 10-dB SL signal), and similarly for the 30- and 40-dB SL signals. The results were consistent with the predictions.

No Need for Templates in the Auditory Enhancement Effect

The audibility of a target tone in a multitone background masker is enhanced by the presentation of a precursor sound consisting of the masker alone. There is evidence that precursor-induced neural adaptation plays a role in this perceptual enhancement. However, the precursor may also be strategically used by listeners as a spectral template of the following masker to better segregate it from the target. In the present study, we tested this hypothesis by measuring the audibility of a target tone in a multitone masker after the presentation of precursors which, in some conditions, were made dissimilar to the masker by gating their components asynchronously. The precursor and the following sound were presented either to the same ear or to opposite ears. In either case, we found no significant difference in the amount of enhancement produced by synchronous and asynchronous precursors. In a second experiment, listeners had to judge whether a synchronous multitone complex contained exactly the same tones as a preceding precursor complex or had one tone less. In this experiment, listeners performed significantly better with synchronous than with asynchronous precursors, showing that asynchronous precursors were poorer perceptual templates of the synchronous multitone complexes. Overall, our findings indicate that precursor-induced auditory enhancement cannot be fully explained by the strategic use of the precursor as a template of the following masker. Our results are consistent with an explanation of enhancement based on selective neural adaptation taking place at a central locus of the auditory system.

What is a melody? On the relationship between pitch and brightness of timbre

Previous studies showed that the perceptual processing of sound sequences is more efficient when the sounds vary in pitch than when they vary in loudness. We show here that sequences of sounds varying in brightness of timbre are processed with the same efficiency as pitch sequences. The sounds used consisted of two simultaneous pure tones one octave apart, and the listeners’ task was to make same/different judgments on pairs of sequences varying in length (one, two, or four sounds). In one condition, brightness of timbre was varied within the sequences by changing the relative level of the two pure tones. In other conditions, pitch was varied by changing fundamental frequency, or loudness was varied by changing the overall level. In all conditions, only two possible sounds could be used in a given sequence, and these two sounds were equally discriminable. When sequence length increased from one to four, discrimination performance decreased substantially for loudness sequences, but to a smaller extent for brightness sequences and pitch sequences. In the latter two conditions, sequence length had a similar effect on performance. These results suggest that the processes dedicated to pitch and brightness analysis, when probed with a sequence-discrimination task, share unexpected similarities.

Effects of age and noise exposure on the representation of amplitude modulation

Age and lifetime noise exposure were used as predictors for electrophysiological and psychophysical measures of amplitude modulation processing. Frequency-following responses (FFRs) were recorded from 61 listeners (20 young, 23 middle-aged, 18 elderly) to 0.6- and 2-kHz, 75-dB SPL, carrier tones amplitude modulated at 100 Hz. A pink noise highpass-filtered at 3 kHz was included to mask basal cochlear contributions to the FFR. Sinusoidal amplitude modulation detection (AMD) thresholds were measured for the same listeners for a 2-kHz carrier (40 and 80 dB SPL) and for three modulation frequencies (25, 50, and 100 Hz). The carrier was presented in notched pink noise to limit off-frequency listening. Lifetime noise exposure was estimated using a structured interview. A regression model was used to determine the independent contributions of age and noise exposure, while controlling for audiometric threshold. FFR amplitude for the 0.6 kHz carrier showed a marked age-related decline. Age was also associated with...

Short-Term Learning and Memory: Training and Perceptual Learning

The frequency-following response (FFR) is a sustained auditory-evoked potential that reflects the phase locking of neurons in the auditory brainstem to periodicities in the waveform of a sound. Studies have shown that short-term auditory training can improve the robustness and/or accuracy of this phase locking. FFR plasticity has been investigated using training tasks that are thought to involve some form of auditory temporal coding, including fundamental-frequency discrimination training, training to identify Mandarin lexical tones, and training to identify speech in noise. The results of these studies have shown that improvements in the trained task are often accompanied by FFR plasticity. This suggests that subcortical auditory processing is not hardwired but can be modified by training even in adulthood. The FFR has also been shown to change following auditory-cognitive training protocols in special populations of listeners who may have subcortical auditory processing deficits, such as children with language-based learning disabilities, elderly listeners, and listeners with sensorineural hearing loss. The results of these studies provide promising evidence that subcortical auditory plasticity could be harnessed to ameliorate auditory processing deficits. It has been hypothesized that this learning-induced subcortical plasticity may be guided by efferent cortical feedback; however, the mechanisms of FFR plasticity remain largely unclear.

The perception of musical consonance beyond the traditional existence region of pitch

The traditional notion that pitch perception breaks down for frequency components above 5 kHz was challenged by a study [Oxenham et al., Proc. Natl. Acad. Sci. U. S. A. 108, 7629-7634 (2011)] showing that complex tones high-pass filtered at 6 kHz convey the perception of melodic intervals. We investigated whether complex tones high-pass filtered above 6 kHz can also convey the perception of harmonic intervals. Eleven listeners rated the pleasantness of consonant and dissonant dyads (two-note chords) consisting of harmonic complex tones band-pass filtered either in a low-frequency (1-6 kHz) or in a high-frequency (7-12 kHz) region. The two tones in each dyad were presented to opposite ears. In the high-frequency condition the dyads were presented with a low-pass noise to mask combination tones. Pleasantness ratings were significantly higher for consonant than for dissonant intervals in both frequency regions. This preference for consonant dyads in the high-frequency region was not observed when the tones w...

Guitarists' evaluation and discrimination of steel-string acoustic guitars built with back/side woods of varying price, prestige, and sustainability

The different woods used for the back plates of acoustic guitars are often compared by guitarists for their sound qualities, but these comparisons are rarely done under blinded conditions. For this experiment, six steel-string acoustic guitars were built to be as similar as possible except for the woods used for the backs and sides. Bridge admittance measurements and spectral analyses of acoustic recordings revealed small differences between the guitars in their low-frequency modes. Fifty-two experienced guitar players rated the guitars for sound quality, playability, and other perceptual attributes while wearing welder’s goggles to prevent visual identification. The guitars received on average similar ratings for sound quality and playability. A factor analysis showed that the other perceptual attributes clustered around the dimensions of “clarity,” “warmth,” and “loudness,” which were all positively related to perceived sound quality, and did not differ significantly between the guitars. An ABX discrimi...

The perceptual effects of tonewood choice for the back/side plates of the steel-string acoustic guitar

The sound qualities of different tonewoods used for the back/side plates of acoustic guitars are the subject of intense debate among guitarists. However, comparisons between different guitars are rarely performed under blinded conditions. We asked a sample of professional, semi-professional, and amateur guitarists (n = 52) to rate the sound quality of six steel-string acoustic guitars, built to be as similar as possible except for the woods used for the back/side plates, which were: Brazilian rosewood, Indian rosewood, mahogany, maple, sapele, and walnut. The guitarists played the guitars in a dimly lit room while wearing welder’s goggles to prevent visual identification. The sound quality ratings did not differ significantly between guitars. Test-retest correlations, measured for a subset of guitarists (n = 34), were low, suggesting that the lack of significant rating differences was not due to averaging out contrasting individual preferences. The results of a blinded ABX discrimination test, performed b...

Erratum to: The Auditory Enhancement Effect is Not Reflected in the 80-Hz Auditory Steady-State Response

Erratum to: JARO DOI 10.1007/s10162-014-0455-y The y-axis scale in Fig. 3 was incorrectly shifted upwards because of a coding error, and the unit of measure in the y-axis label was incorrectly reported as μV instead of μV2. The correct figure is shown below. FIG. 3 A ASSR levels for the background components as a function of precursor type. B ASSR levels for the target component as a function of precursor type. Each colored point represents an individual listener. The color code is the same as in Figure 2. The ...