Vocal Responses Research Articles

Slowed Compensation Responses to Altered Auditory Feedback in Post-Stroke Aphasia: Implications for Speech Sensorimotor Integration

Developing a clearer understanding of impairments that underlie the behavioral characteristics of aphasia is essential for the development of targeted treatments and will help inform theories of speech motor control. Impairments in sensorimotor integration of speech in individuals with conduction aphasia have previously been implicated in their repetition deficits. However, much less is known about the extent to which these integrative deficits occur outside of conduction aphasia and how this manifests behaviorally in areas other than speech repetition. In this study, we aimed to address these issues by examining the behavioral correlates of speech sensorimotor impairment under altered auditory feedback (AAF) and their relationship with the impaired ability to independently correct for online errors during picture naming in people with aphasia. We found that people with aphasia generate slower vocal compensation response to pitch-shift AAF stimuli compared with controls. However, when the timing of responses was controlled for, no significant difference in the magnitude of vocal pitch compensation was observed between aphasia and control groups. Moreover, no relationship was found between self-correction of naming errors and the timing and magnitude of vocal compensation responses to AAF. These findings suggest that slowed compensation is a potential behavioral marker of impaired sensorimotor integration in aphasia.

Anthropogenic noise affects female, not male house wren response to change in signaling network

AbstractVocal signals mediate social relationships, and among networks of territorial animals, information is often shared via broadcast vocalizations. Anthropogenic noise may disrupt communication among individuals within networks, as animals change the way they vocalize in noise. Furthermore, constraints on signal transmission, including frequency masking and distance, may affect information exchange following a disruption in social networks. We tested the hypothesis that signaling interactions within networks of breeding male and female house wrens (Troglodytes aedon) depend on distance, ambient noise, and receiver nesting stage. We used playback experiments to simulate territorial intrusions with and without noise playbacks on the territories of established males and simultaneously recorded the vocal responses of neighbors. To examine whether intrusions impacted interactions between males, we used randomization tests to determine whether treatment, distance, noise, or nesting stage affected vocal coordination between challenged and neighboring males. We also quantified singing patterns to explore whether intrusions on territories of challenged males affected singing by males and females on neighboring territories. Males sang at the lowest rates and were less likely to overlap songs with the challenged male when their partner was laying, compared to males during early and late nesting stages. Noise and distance did not affect vocal coordination or male singing rates. Fewer females sang during the intruder‐only treatment compared to the control and intrusions with noise. Added noise in the territories of challenged males may have masked signals, and as a result, females only changed their behavior during the intruder‐only treatment. Our results suggest that the fertility of breeding partners may be more important to males than short‐term changes on rival male territories. Elevated noise did little to alter male responses to threats within networks. Females appeared to eavesdrop on interactions involving neighboring males, but noise may have prevented detection of their interactions.

Optimal Methods of Documenting Analgesic Efficacy in Neonatal Piglets Undergoing Castration

Simple SummarySurgical castration in piglets is widely used in commercial pig production systems; however, it may cause pain and stress to the animal. There is an urgent need to develop effective pain-relieving medications to use for this procedure. Such products must meet high standards of proof confirming that they are effective. This requires undertaking trials to determine the duration and severity of pain that piglets experience during and after castration, and the extent of pain reduction in anaesthetic/analgesic treated piglets. Unfortunately, responses to pain may be transient, subtle, or variably expressed. Furthermore, there is no simple “gold standard” method to measure pain in neonatal piglets. Instead, researchers must rely on using a range of indirect measures of pain of varying reliability. Without understanding the nature of expression of piglet pain, and the reliability of test measures to detect it, there is the potential of misinterpreting trial outcomes. Although there is a high degree of variability in the literature of test methods employed and outcomes obtained, there is nevertheless a growing body of evidence to suggest that some piglet responses to pain induced by castration, are more consistently reproduced and specific to the pain experienced during castration than others. In this narrative review, we examine the potential indicators of pain in neonatal piglets undergoing castration to determine the optimal methods currently available to most accurately detect pain and assess pain mitigation.Analgesic products for piglet castration are critically needed. This requires extensive animal experimentation such as to meet regulatory-required proof of efficacy. At present, there are no validated methods of assessing pain in neonatal piglets. This poses challenges for investigators to optimize trial design and to meet ethical obligations to minimize the number of animals needed. Pain in neonatal piglets may be subtle, transient, and/or variably expressed and, in the absence of validated methods, investigators must rely on using a range of biochemical, physiological and behavioural variables, many of which appear to have very low (or unknown) sensitivity or specificity for documenting pain, or pain-relieving effects. A previous systematic review of this subject was hampered by the high degree of variability in the literature base both in terms of methods used to assess pain and pain mitigation, as well as in outcomes reported. In this setting we provide a narrative review to assist in determining the optimal methods currently available to detect piglet pain during castration and methods to mitigate castration-induced pain. In overview, the optimal outcome variables identified are nociceptive motor and vocal response scores during castration and quantitative sensory-threshold response testing and pain-associated behaviour scores following castration.

White-handed gibbons discriminate context-specific song compositions

White-handed gibbons produce loud and acoustically complex songs when interacting with their neighbours or when encountering predators. In both contexts, songs are assembled from a small number of units although their composition differs in context-specific ways. Here, we investigated whether wild gibbons could infer the ‘meaning’ when hearing exemplars recorded in both contexts (i.e. ‘duet songs’ vs. ‘predator songs’). We carried out a playback experiment by which we simulated the presence of a neighbouring group producing either its duet or a predator song in order to compare subjects’ vocal and locomotor responses. When hearing a recording of a duet song, subjects reliably responded with their own duet song, which sometimes elicited further duet songs in adjacent groups. When hearing a recording of a predator song, however, subjects typically remained silent, apart from one of six groups which replied with its own predator song. Moreover, in two of six trials, playbacks of predator songs elicited predator song replies in non-adjacent groups. Finally, all groups showed strong anti-predator behaviour to predator songs but never to duet songs. We concluded that white-handed gibbons discriminated between the two song types and were able to infer meaning from them. We discuss the implications of these findings in light of the current debate on the evolutionary origins of syntax.

Effect of maternal depression on infant-directed speech to prelinguistic infants: Implications for language development.

The nature and timing of caregivers’ speech provides an important foundation for infant attention and language development in the first year of life. Infant-directed speech is a key component of responsive parent-infant communication that is typically characterised by exaggerated intonation and positive affect. This study examines the effect of postnatal depression on the expression of positive vocal affect and pitch, the quantity of mothers’ infant-directed speech input and the timing of vocal responses between mother and infant. Postnatal mothers currently experiencing symptoms of depression (n = 13) were matched to postnatal mothers who were not experiencing symptoms of depression (n = 13), and audio-recorded while playing with their 6-month-old infants. Compared with depressed mothers, non-depressed mothers used a higher mean pitch and pitch range, spoke more, gave faster verbal responses and were rated as expressing more positive valence in their voice. These preliminary findings indicate that mothers experiencing low mood use less infant-directed speech and less exaggerated pitch with prelinguistic infants. Postnatal depression is a major health issue that adversely impacts the parent and child. Early interventions for PND may benefit from identifying ways to support the timing of conversations and mothers’ use of appropriate vocal pitch and infant-directed speech modifications. Further research is needed to confirm whether these strategies support early conversations.

Deep Brain Stimulation Does Not Modulate Auditory-Motor Integration of Speech in Parkinson's Disease.

Deep brain stimulation (DBS) has significant effects on motor symptoms in Parkinson's disease (PD), but existing studies on the effect of DBS on speech are rather inconclusive. It is assumed that deficits in auditory-motor integration strongly contribute to Parkinsonian speech pathology. The aim of the present study was to assess whether subthalamic DBS can modulate these deficits. Twenty PD patients (15 male, 5 female; 62.4 ± 6.7 years) with subthalamic DBS were exposed to pitch-shifted acoustic feedback during vowel vocalization and subsequent listening. Voice and brain activity were measured ON and OFF stimulation using magnetoencephalography (MEG). Vocal responses and auditory evoked responses time locked to the onset of pitch-shifted feedback were examined. A positive correlation between vocal response magnitude and pitch variability was observed for both, stimulation ON and OFF (ON: r = 0.722, p < 0.001, OFF: r = 0.746, p < 0.001). However, no differences of vocal responses to pitch-shifted feedback between the stimulation conditions were found [t(19) = −0.245, p = 0.809, d = −0.055]. P200m amplitudes of event related fields (ERF) of left and right auditory cortex (AC) and superior temporal gyrus (STG) were significantly larger during listening [left AC P200m: F(1, 19) = 10.241, p = 0.005, f = 0.734; right STG P200m: F(1, 19) = 8.393, p = 0.009, f = 0.664]. Subthalamic DBS appears to have no substantial effect on vocal compensations, although it has been suggested that auditory-motor integration deficits contribute to higher vocal response magnitudes in pitch perturbation experiments with PD patients. Thus, DBS seems to be limited in modulating auditory-motor integration of speech in PD.

Automatic Assessment of Language Ability in Children with and without Typical Development.

This study describes a fully automated method of expressive language assessment based on vocal responses of children to a sentence repetition task (SRT), a language test that taps into core language skills. Our proposed method automatically transcribes the vocal responses using a test-specific automatic speech recognition system. From the transcriptions, a regression model predicts the gold standard test scores provided by speech-language pathologists. Our preliminary experimental results on audio recordings of 104 children (43 with typical development and 61 with a neurodevelopmental disorder) verifies the feasibility of the proposed automatic method for predicting gold standard scores on this language test, with averaged mean absolute error of 6.52 (on a observed score range from 0 to 90 with a mean value of 49.56) between observed and predicted ratings.Clinical relevance-We describe the use of fully automatic voice-based scoring in language assessment including the clinical impact this development may have on the field of speech-language pathology. The automated test also creates a technological foundation for the computerization of a broad array of tests for voice-based language assessment.

Singing behaviour of ruby‐crowned kinglets Regulus calendula in relation to time‐of‐day, time‐of‐year and social context

Observational field studies provide insight on the multifunctional nature of birdsong. For example, if song production were limited to pre‐fertilization, then that would suggest a mate attraction function. If it were used throughout the breeding season and in response to intruding males, then that would suggest a territorial defence function. In the present study, we determined the daily and seasonal singing patterns of male ruby‐crowned kinglets Regulus calendula in Labrador, Canada, using microphone arrays in two breeding seasons. Using a playback experiment, we simulated a territorial intrusion to compare the structure of songs produced while defending a territory to the structure of songs produced during solo and contest singing. Singing peaked in the early part of the breeding season and then declined continuously for the remainder of the season, which suggests that the songs function in mate attraction. Singing peaked 2–3 h after dawn, and then declined steadily until it stopped at 10 pm. Some nocturnal singing was observed, but no dawn singing was observed. A high probability of signal overlap by heterospecific songs at dawn would hinder signal recognition and explain the observed delay in peak singing activity. Vocal responses to playback suggested a function in territory defence. However, there were no significant differences in the duty cycle, frequency modulation and bandwidth of songs in relation to the context of song production, though songs were shorter in the intrusion context than during solo singing. Overall, the study provides the first quantitative description of the effects of time of day, time of year and social context on singing behaviour in this understudied species.

Playback of Alarm and Appetitive Calls Differentially Impacts Vocal, Heart-Rate and Motor Response in Rats

Our rudimentary knowledge about intraspecific vocal communication systems in rats is limited by suitable technical and experimental models. Rats emit 50-kHz ultrasonic vocalizations in appetitive states and 22-kHz in aversive states. Both affective states influence heart rate. Here, we propose a novel behavioral model employing pre-recorded playbacks, to which vocalizations, heart rate and distance traveled in response were measured. Fifty-kHz playbacks elicited the most vocalizations (>60 calls per minute, mostly in 50-kHz range), increased heart rate and movement. These changes were more pronounced in singly housed rats compared to the paired housed group. In contrast, 22-kHz playback lead to prolonged heart rate drop and decrease in locomotor activity. The effects evoked by natural playback were more pronounced than their corresponding artificial tones. The correlations between vocalizations, heart rate and movement all point to common regulatory mechanisms. This is the first description of heart rate changes following playback of rat vocalizations.

High Security and Capacity of Image Steganography for Hiding Human Speech Based on Spatial and Cepstral Domains

A new technique of hiding a speech signal clip inside a digital color image is proposed in this paper to improve steganography security and loading capacity. The suggested technique of image steganography is achieved using both spatial and cepstral domains, where the Mel-frequency cepstral coefficients (MFCCs) are adopted, as very efficient features of the speech signal. The presented technique in this paper contributes to improving the image steganography features through two approaches. First is to support the hiding capacity by the usage of the extracted MFCCs features and pitches extracted from the speech signal and embed them inside the cover color image rather than directly hiding the whole samples of the digitized speech signal. Second is to improve the data security by hiding the secret data (MFCCs features) anywhere in the host image rather than directly using the least significant bits substitution of the cover image. At the recovering side, the proposed approach recovers these hidden features and using them to reconstruct the speech waveform again by inverting the steps of MFCCs extraction to recover an approximated vocal tract response and combine it with recovered pitch based excitation signal. The results show a peak signal to noise ratio of 52.4 dB of the stego-image, which reflect a very good quality and a reduction ratio of embedded data to about (6%–25%). In addition, the results show a speech reconstruction degree of about 94.24% correlation with the original speech signal.

Exploratory dynamics of vocal foraging during infant-caregiver communication

We investigated the hypothesis that infants search in an acoustic space for vocalisations that elicit adult utterances and vice versa, inspired by research on animal and human foraging. Infant-worn recorders were used to collect day-long audio recordings, and infant speech-related and adult vocalisation onsets and offsets were automatically identified. We examined vocalisation-to-vocalisation steps, focusing on inter-vocalisation time intervals and distances in an acoustic space defined by mean pitch and mean amplitude, measured from the child’s perspective. Infant inter-vocalisation intervals were shorter immediately following a vocal response from an adult. Adult intervals were shorter following an infant response and adult inter-vocalisation pitch differences were smaller following the receipt of a vocal response from the infant. These findings are consistent with the hypothesis that infants and caregivers are foraging vocally for social input. Increasing infant age was associated with changes in inter-vocalisation step sizes for both infants and adults, and we found associations between response likelihood and acoustic characteristics. Future work is needed to determine the impact of different labelling methods and of automatic labelling errors on the results. The study represents a novel application of foraging theory, demonstrating how infant behaviour and infant-caregiver interaction can be characterised as foraging processes.

The Inadvertent Effects of PECS on Vocal Responding of Children with Autism Spectrum Disorder

The Picture Exchange Communication System (PECS) is a widely used alternative and augmentative communication (AAC) system for children with autism spectrum disorder (ASD) who have limited or no vocal abilities. Vocalizations may emerge with the use of PECS particularly during the training phases. One question that often arises is what effect continued use of PECS has on vocal behavior. The current study evaluated the effects of PECS on vocal responding for participants who had been using PECS for at least 1 year. Four children with ASD participated in this study. Each had functional vocal communication skills but used PECS as their primary mode of communication. One of the participants also used sign language. The effects of PECS on vocal responding were evaluated in two studies using a reversal design. The use of PECS inhibited vocal responding if both modes of communication were on the same schedule of reinforcement. When PECS was placed on extinction (study 1) or removed (study 2), vocal responding increased across subjects. If vocal responding and PECS remain on the same schedule of reinforcement, vocal responses may be suppressed and, consequently, improvements in functional vocal communication may not be seen. Additional studies are needed to replicate the current findings as well as to determine if PECS should be faded if functional vocal communication is established.

Two sources of task prioritization: The interplay of effector-based and task\xa0order-based capacity allocation in the PRP paradigm

When processing of two tasks overlaps, performance is known to suffer. In the well-established psychological refractory period (PRP) paradigm, tasks are triggered by two stimuli with a short temporal delay (stimulus onset asynchrony; SOA), thereby allowing control of the degree of task overlap. A decrease of the SOA reliably yields longer RTs of the task associated with the second stimulus (Task 2) while performance in the other task (Task 1) remains largely unaffected. This Task 2-specific SOA effect is usually interpreted in terms of central capacity limitations. Particularly, it has been assumed that response selection in Task 2 is delayed due to the allocation of less capacity until this process has been completed in Task 1. Recently, another important factor determining task prioritization has been proposed—namely, the particular effector systems associated with tasks. Here, we study both sources of task prioritization simultaneously by systematically combining three different effector systems (pairwise combinations of oculomotor, vocal, and manual responses) in the PRP paradigm. Specifically, we asked whether task order-based task prioritization (SOA effect) is modulated as a function of Task 2 effector system. The results indicate a modulation of SOA effects when the same (oculomotor) Task 1 is combined with a vocal versus a manual Task 2. This is incompatible with the assumption that SOA effects are solely determined by Task 1 response selection duration. Instead, they support the view that dual-task processing bottlenecks are resolved by establishing a capacity allocation scheme fed by multiple input factors, including attentional weights associated with particular effector systems.

Diverging changes in rat striatal extracellular dopamine and DOPAC levels and in frequency-modulated 50-kHz ultrasonic vocalizations rate during repeated amphetamine treatment

One characteristic feature of addictive drugs is their ability to induce, after a single exposure, a lasting sensitization to the next doses; the underlying neuroplastic changes supposedly involve the brain dopamine system. We aimed at identifying putative relationships between alterations in extracellular dorsal striatal dopamine, HVA and DOPAC levels and in frequency-modulated 50-kHz ultrasonic vocalizations rate response during repeated intraperitoneal amphetamine treatment. Measurements were performed before and after amphetamine doses 1, 2, 7 and 8 (Amph1, Amph2, Amph7 and Amph8; treatment days 1, 7, 12 and 23, respectively). Amphetamine was confirmed to induce sensitization of the vocalization response, but an extended recording time (180 instead of 20 min) revealed that sensitization of this response requires more time to develop than hitherto believed. Baseline extracellular dopamine level increased initially, declined after a series of daily amphetamine doses and showed some tendency for recovery after drug withdrawal. Baseline extracellular DOPAC (but not HVA) showed a continuous decline during the treatment. There was no significant change in the integrated short-term (3-h) extracellular dopamine response, whereas the respective DOPAC collection lowered significantly after repeated drug treatment. Extracellular DOPAC is believed to originate mostly from newly synthesized dopamine, hence the declines in its baseline and post-amphetamine levels suggest falling dopamine synthesis. These results indicate that sensitization of the appetitive vocalization response to amphetamine continues despite reduced dorsal striatal dopamine synthesis and involves no changes in amphetamine-induced dopamine release.

Citizen science contribution to national wolf population monitoring: what have we learned?

Evidence-based management of large carnivores is a crucial step towards their effective conservation. However, monitoring of these populations is demanding and generally requires substantial fieldwork effort. Lately, citizen science has become an increasingly important part of wildlife monitoring, but can that endanger studied species? In this paper, we describe our experiences with recruiting and involving volunteers in annual howling surveys of grey wolf (Canis lupus) population in Slovenia and present the framework about the use of citizens for collecting data. Huge effort of participants in a 7-year-long monitoring at a national scale has yielded a total of 116 wolf vocal responses, including 53 confirmed litters. Annually, between 5 and 12 reproductive packs were detected and an increasing trend in wolf population throughout the study period was observed. Volunteer-based howling surveys proved to be a cost-effective method for detection of reproductive packs on a large spatial scale, offering an insight into wolf population trends across a longer time period and we provide some recommendations for organisation and coordination of surveys. We also discuss ethical issues raised from our experience in using citizen science for this purpose.

Call production induces motor-driven ZENK response in the song control system of black-capped chickadees

Imitative vocal learning has now been described in a variety of taxa, but is most extensively studied for birdsong learning. However, songbirds produce a variety of songs and calls that also are learned. For example, black-capped chickadees, Poecile atricapillus, produce a variety of highly complex learned vocalizations that they use in different contexts. The role of the neural song control system, including the HVC and the robust nucleus of the arcopallium (RA), in the production of chickadee calls is unclear. In this experiment, birds were housed in different conditions to elicit fee-bee songs and gargle, chick-a-dee and tseet calls. The birds were exposed to different stimuli (i.e. a novel live chickadee, a stuffed saw-whet owl, Aegolius acadicus, a mirror, or long-day photoperiods) and their behavioural and vocal responses were recorded. Brains were then processed to label immediate early gene (ZENK) immunoreactivity. In both HVC and RA, the gargle call elicited the most ZENK immunoreactivity. Although the fee-bee song is well established to depend on imitative vocal learning, its production did not induce the most motor-driven ZENK. These findings suggest that activity in the song control system may be more closely correlated with the acoustic complexity of learned vocalizations than with the extent of imitative learning required during development. These findings, and those of earlier studies, indicate that the neural circuit commonly referred to as the ‘song control system’ is better described as a vocal control system for learned vocalizations.

Beneficial Effects of Fingolimod on Social Interaction, CNS and Peripheral Immune Response in the BTBR Mouse Model of Autism

Autism Spectrum Disorders (ASD) are neurodevelopmental disorders characterized by social communication deficits and repetitive/stereotyped behaviours. We evaluated the effects of a chronic treatment with the immunomodulator drug Fingolimod (FTY720 – a non-selective Sphingosine 1-Phosphate Receptor ligand) in an ASD model, the BTBR T+tf/J (BTBR) mouse strain. In adult BTBR males, chronic FTY720 treatment (4 weeks) increased social and vocal response during a male–female interaction and hippocampal expression of BDNF and Neuregulin 1, two trophic factors reduced in BTBR when compared to control C57 mice. FTY720 also re-established the expression of IL-1β and MnSOD in the hippocampus, whereas it did not modify IL-6 mRNA content. In addition to its central effect, FTY720 modulated the activation state of peripheral macrophages in the BTBR model, both in basal conditions and after stimulation with an immune challenge. Furthermore, IL-6 mRNA colonic content of BTBR mice, reduced when compared with C57 mice, was normalized by chronic treatment with FTY720. Our study, while indicating FTY720 as a tool to attenuate relevant alterations of the BTBR neurobehavioural phenotype, emphasizes the importance of gut mucosal immune evaluation as an additional target that deserve to be investigated in preclinical studies of anti-inflammatory therapeutic approaches in ASD.

A Six-Minute Measure of Vocalizations in Toddlers with Autism Spectrum Disorder.

To improve early identification of autism spectrum disorder (ASD), we need objective, reliable, and accessible measures. To that end, a previous study demonstrated that a tablet-based application (app) that assessed several autism risk behaviors distinguished between toddlers with ASD and non-ASD toddlers. Using vocal data collected during this study, we investigated whether vocalizations uttered during administration of this app can distinguish among toddlers aged 16-31 months with typical development (TD), language or developmental delay (DLD), and ASD. Participant's visual and vocal responses were recorded using the camera and microphone in a tablet while toddlers watched movies designed to elicit behaviors associated with risk for ASD. Vocalizations were then coded offline. Results showed that (a) children with ASD and DLD were less likely to produce words during app administration than TD participants; (b) the ratio of syllabic vocalizations to all vocalizations was higher among TD than ASD or DLD participants; and (c) the rates of nonsyllabic vocalizations were higher in the ASD group than in either the TD or DLD groups. Those producing more nonsyllabic vocalizations were 24 times more likely to be diagnosed with ASD. These results lend support to previous findings that early vocalizations might be useful in identifying risk for ASD in toddlers and demonstrate the feasibility of using a scalable tablet-based app for assessing vocalizations in the context of a routine pediatric visit. LAY SUMMARY: Although parents often report symptoms of autism spectrum disorder (ASD) in infancy, we are not yet reliably diagnosing ASD until much later in development. A previous study tested a tablet-based application (app) that recorded behaviors we know are associated with ASD to help identify children at risk for the disorder. Here we measured how children vocalize while they watched the movies presented on the tablet. Children with ASD were less likely to produce words, less likely to produce speechlike sounds, and more likely to produce atypical sounds while watching these movies. These measures, combined with other behaviors measured by the app, might help identify which children should be evaluated for ASD. Autism Res 2020, 13: 1373-1382. © 2020 International Society for Autism Research, Wiley Periodicals, Inc.

Neutral stimuli and pupillometric task conflict.

It has been suggested that the interference in the Stroop task arises due to both information conflict (color vs. word meaning) and task conflict (respond to the color vs. read the word). Interestingly, the task conflict (faster responses in the congruent condition compared to the neutral condition) is influenced by the readability of the stimulus. However, behavioral results indicate the influence of the contribution of readability to the task conflict appears only when vocal responses are required. We conducted a Stroop experiment with four readability levels of neutrals. Participants were required to respond manually, and both their response times and pupil dilation were measured. Our results showed the slowest responses for incongruent trials and the fastest responses for congruent trials. However, no differences in responses were found between the readability levels of the neutrals. In contrast, pupil dilation showed the largest dilation in the incongruent trials and smallest dilation in the neutral trials. In addition, the differences between congruent and neutral trials were influenced by the readability of the stimulus. Specifically, unreadable neutral stimuli showed meaningful differences early on, which also remained for longer time compared with readable neutral stimuli. These results are important and can help in specifying new requirements regarding the theory and modeling of the Stroop task; in particular, studies that want to control the neutrality of their neutral trials should take the readability into account.

Experimental study of alarm calls of the oriental tit (Parus minor) toward different predators and reactions they induce in nestlings

AbstractAnti‐predatory strategies of birds are diverse and may include predator‐specific alarm calls. For example, oriental tit (Parus minor) parents can distinguish snakes from other predators and produce snake‐specific referential vocalizations ("jar" call) when a snake poses a threat to their nest. The “jar” call has a very specific function to induce fledging of nestlings close to fledging age. This reaction ensures nestlings' survival in natural encounters with snakes that are capable of entering nest cavities and kill entire broods. Sciurid rodents, like chipmunks, may pose a similar threat to cavity‐nesting birds. We explored the hypothesis that parents use the fledging‐inducing alarm vocalizations in this situation, because chipmunks, like snakes, can kill the brood upon entering the nest cavity. We compared alarm calls of parents toward two predators (chipmunk and snake) who pose a similar threat to the nestlings in a nest cavity, and toward an avian predator (Eurasian jay) who cannot enter nest cavities and poses no threat to the nestlings in a nest. Our results show that the vocal responses of oriental tits were different among the three predators. This suggests that the acoustic properties of vocal responses to predators are different between predators of a similar hunting strategy (nest‐cavity entering). The playback of recorded vocal responses of parents to chipmunks did not trigger the fledging of old nestlings, whereas the vocalizations toward a snake did, as shown by earlier studies. Our study suggests that the vocal response of parents does not carry information about the ability of predators to enter the nest cavity and confirms the special status of alarm calls triggered by snakes.