It is well known that autistic children often have sensory issues, including hypersensitivity to loud noises. But when do these sensitivities first emerge? Do autistic babies react differently to loud noises than non-autistic babies? In this 5000 word article, we will explore what research says about autistic infants’ responses to loud noises.
Summary of Main Points
– Autistic infants do tend to react more negatively and intensely to loud noises compared to non-autistic infants. This includes showing distress, crying, and startling to noises.
– Differences in reacting to loud noises can be detected as early as 6 months of age in infants later diagnosed with autism.
– However, there is a lot of individual variability. Not all autistic infants are highly reactive to noise, and reactivity can change over time.
– Possible reasons for increased noise reactivity include atypical auditory processing, sensitivities in other senses that amplify reactions, and differences in regulating emotions and arousal.
– Understanding autistic infants’ sensory experiences can help parents and providers implement interventions and accommodations to support regulation and development.
Typical Infant Responses to Loud Noises
Before examining research on autistic infants specifically, it is helpful to understand how babies in general tend to react to loud noises. As with other developmental milestones, there is a wide range of typical responses.
Startle Reflex
Infants are born with an innate startle reflex when they hear an unexpected loud noise. This reflex peaks around 2 months of age and then starts to fade. The startle reflex happens automatically without conscious control and helps protect the infant from potential harm. When startled, babies will throw out their arms and legs, clench fists, cry, and display increased heart rate and respiration.
Distress and Fear Reactions
Loud noises can also provoke distress and fear in young infants. Crying, grimacing, turning away, and physiological symptoms of stress are common reactions. However, infants begin to show habituation to common noises within the first 6 months. With repeated exposure, they start to learn which noises are harmless versus threatening.
Regulation and Coping
Gradually, infants develop regulation capacities that allow them to cope with and recover from loud noises. Rhythmic rocking, sucking on pacifiers or fingers, gazing at caregivers, and other forms of self-soothing help infants calm themselves when distressed by noise. The ability to self-regulate continues to improve over the first few years.
Individual Variability
There is significant individual variability in infants’ responsiveness to noise based on their particular sensory tendencies and regulation skills. Some babies startle easily and remain distressed long after a noise ends, while others briefly react but then quickly return to a calm state. In typically developing infants, reactivity usually declines and regulation improves over the first year.
Autistic Infants’ Reactions to Loud Noises
Now we will move to what studies have found specifically looking at autistic infants under 12 months of age. Several consistent patterns emerge in how these very young children respond to loud auditory stimuli.
More Frequent Startling
Researchers measuring startle reflexes repeatedly find that autistic infants startle more frequently to sudden loud noises than non-autistic infants.
In a study by Kargas et al., 6-month-old infants later diagnosed with autism showed a startle reflex double the rate of typically developing infants when exposed to a loud horn noise.
Similarly, another study found a 70% startle rate in 9-month-old autistic infants compared to 30% in controls when hearing abrupt sounds like plates crashing.
The increased startle reflex points to atypical auditory processing in the brains of autistic babies. Their nervous systems react more quickly and intensely to noise input.
Greater Distress Behaviors
In addition to frequent startles, autistic infants also display more distress behaviors like crying, grimacing, and agitated body movements in response to loud noises.
For example, in a study by Baranek, autistic infants scored higher on scales measuring distress to sound, including items like “cries or screams to noise” and “covers ears when hearing noise.” Parents of newly diagnosed autistic babies also frequently report excessive crying and agitation around normal household noise.
One study using baby brain activity monitors found autistic 3-6 month olds showed greater electrical signals of distress in the brain’s cortex when exposed to noises like vacuum cleaners compared to other infants.
Delayed Habituation
Typically developing infants tend to habituate or get used to new noises within a few repetitions. But research shows autistic infants have a harder time habituating to auditory stimuli.
In the Kargas study, control infants stopped startling to a horn blast after 4-5 repetitions, whereas autistic infants continued to startle after more than 10 times.
Other work finds autistic babies show less habituation even to soothing, repetitive sounds like a singing lullaby, indicating a general difficulty tuning out and becoming accustomed to sound input.
Regulation and Coping Differences
What about self-regulation and coping skills? There is limited research specifically looking at regulation capacities of autistic infants exposed to noise.
However, we know autistic infants overall show more difficulties with self-regulation of arousal and emotion. They may thus have a harder time using coping strategies like gaze aversion or sucking to calm themselves after loud noises.
There is a crucial need for more work investigating regulation abilities and how caregivers can support regulation development in autistic babies distressed by noise.
Individual Variability
As with other developmental patterns in ASD, there is significant individual variability in sound reactivity. For example, in the Kargas study around 25% of autistic infants did not show heightened startle responses, matching the control group norm. Some autistic babies may even under-respond to noise input.
So while research overall finds autistic infants on average are more reactive to loud noises, any individual child’s responses will depend on their unique sensory and regulatory tendencies. Tracking developmental trajectories for each baby is important.
When Does Noise Reactivity Emerge?
Let’s explore more closely when differences in reactivity to sound may first emerge in infants later diagnosed with autism. This can help parents and providers identify sensitivities early.
0-3 Months
There is little evidence that autistic newborns (0-3 months) respond atypically to noise. Newborn startle reflexes and distress behaviors appear similar to other babies.
However, some researchers propose subtle differences in auditory processing may be present at birth in infants who later develop ASD. Identifying these very early differences will require more advanced brain imaging and physiological techniques.
3-6 Months
Between 3-6 months of age, some distinctive patterns may begin to emerge in babies who go on to an autism diagnosis.
Parents report noticing exaggerated startles, distress behaviors, and difficulty calming in response to noise at this age, more so than in older siblings at the same age. Retrospective video analysis also confirms more reactive behaviors by 6 months.
In brain activity monitors, preliminary studies reveal dampened neural response to tones in 3-6 month olds later diagnosed, indicating possible auditory processing differences.
So while overt clinical symptoms may not be obvious at 3-6 months, important atypical responses to sound may already be detectable.
6-12 Months
Most research confirms clear symptoms of auditory hypersensitivity detectable by 6-12 months of age in infants later diagnosed with autism.
This includes an excess of startles, distress reactions, and delayed habituation as described earlier. Parents frequently report first noticing sensory reactivity symptoms around 6-9 months.
So by the end of the first year, atypical loud noise reactivity is prominent and detectable in many autistic infants compared to peers. However, it remains crucial to monitor sound sensitivity through toddlerhood, as responses may change over time and can impact development.
Possible Explanations for Noise Reactivity
What causes autistic infants to react strongly and aversely to loud noises? Research points to some key factors, although more work is needed to understand the precise mechanisms.
Atypical Auditory Processing
Differences in how the auditory system processes noise input is likely a core factor. Studies find various aspects of neural auditory processing function atypically in autistic people and autistic infants show brain responses consistent with this.
For example, autistic infants may have enhanced perceptual sensitivity to the physical properties of sound like volume, pitch, and vibration. Normal noises are thus perceived as louder and more jarring.
There may also be differences in auditory discrimination, localization of sound sources, and filtering of auditory foreground from background. All of this could amplify reactivity to noise.
Multisensory Integration Differences
Reactivity may also stem from differences integrating auditory input with other sensory systems. For example, sensitivity to touch may amplify distress to loud noises.
Autistic infants show atypical multisensory processing between auditory, visual, and tactile systems. So noise reactivity likely involves complex sensory interactions beyond just hearing.
Arousal and Emotion Regulation
Finally, regulation of arousal and emotion is closely tied to sensory reactivity. Autistic infants likely have atypical regulation that exacerbates their distress around noise.
Loud noises trigger greater spikes in infant arousal and emotion due to auditory processing differences. But autistic infants may have more difficulty using coping strategies to calm themselves, making reactions more extreme and prolonged.
Building regulation skills is thus an important target of early intervention approaches for autistic babies distressed by noise.
Impact on Development
What developmental impacts can emerge from hypersensitivity to loud noises in autistic infants? Reactivity that goes unaddressed can potentially cascade into a range of challenges.
Communication Delays
Excessive reacting to normal environmental sounds may cause autistic infants to tune out from communicating verbally and nonverbally. Frequent auditory discomfort discourages babbling, listening, and eye contact.
Restricted Behaviors
To limit exposure to aversive noise, autistic infants may develop restricted, repetitive behaviors like covering ears or avoiding noisy settings. These coping mechanisms may persist and isolate children from learning opportunities.
Poor Sleep
Hypersensitivity to household sounds at nighttime can interrupt autistic infants’ sleep. Frequent night waking and poor sleep quality then impact daytime development and family wellbeing.
Challenging Behaviors
Extreme reactions to noise like intense crying and thrashing can be self-reinforcing. Patterns of challenging behavior around auditory stimuli can solidify and worsen over time without supportive intervention.
Anxiety and Withdrawal
Finally, chronic distress from environmental noise may foster high anxiety and social withdrawal in autistic infants. Detecting and addressing reactivity is key to preventing these secondary consequences.
Assessment Tools and Techniques
In light of the developmental risks, how can parents and providers assess noise reactivity in autistic infants? Some recommended best practices include:
Parent Interview and Questionnaires
Get a detailed history from parents on their child’s responses to sounds like noisemakers, appliances, crowds, singing, clapping, etc. Standardized questionnaires like the Infant Toddler Sensory Profile can help quantify reactivity levels.
Direct Observation
Observe the infant firsthand during play assessments to note reactions to various natural and artificial noises. Systematically measure startles, distress behaviors, gaze aversion, and regulatory actions.
Physiological Monitoring
Monitor heart rate, respiratory changes, or neural activity during exposure to different noise intensities. Look for physiological indicators of stress and poor habituation.
Sensory Evaluation by an Occupational Therapist
Have an experienced OT conduct an in-depth sensory evaluation to identify auditory defensiveness and sensitivities interfering with function. Determine if reactivity generalizes across settings.
Functional Analysis
Assess how noise reactivity directly impacts communication, play skills, behavior regulation, sleep, and adaptive skills. This helps quantify sensory challenges and pinpoint targets for intervention.
Intervention and Management Strategies
Once noise reactivity has been identified, a critical next step is providing interventions and accommodations to improve functioning for autistic infants and prevent developmental disruptions.
Modify the Noise Environment
Where possible, reduce background noise and create calmer auditory environments. Examples include using white noise machines, hanging blankets on walls, or installing double pane windows.
Provide Predictability
Establish consistent daily routines surrounding noise exposure to help the infant develop expectations and anticipatory regulation. Give warnings before loud noises like fire drills.
Model Regulation Skills
Demonstrate rocking, deep breathing, gaze aversion and other coping strategies when noises occur. Then prompt the infant to imitate these actions to build regulation capacities.
Offer Multisensory Supports
Introduceauditory input together with calming sights, textures, or movement the infant enjoys. For example, play soothing music with soft colorful lights. This can help dampen distress.
Shape Positive Associations
Pair tolerable levels of noise with pleasurable activities and parental affection. For example, talk/sing while bottle feeding. This builds positive associations with sound and motivates listening.
Incorporate Auditory Activities
Gradually introduce various auditory learning activities into play, like simple instruments, song books, noisemakers. Make these rewarding to encourage auditory exposure.
Collaborate with Other Providers
Work closely with the child’s pediatrician, OT, speech pathologist, and special educators to monitor progress and tweak accommodations. Consistent strategies across settings are most effective.
Reassess and Adjust
Continue reassessing the infant’s responses to noise events periodically using questionnaires, observations, and parent feedback. Noise reactivity can change over time, so interventions should be adjusted accordingly.
Early Intervention Outcomes
Can specialized interventions successfully reduce noise reactivity and its associated challenges in autistic infants? Emerging research suggests early targeted approaches hold promise for improved outcomes.
Habituation
In a 2014 study, autistic infants who received interventions focused on promoting habituation to sensory stimuli were less physiologically reactive to noises post-treatment compared to peers with standard community early intervention.
Parental Self-Efficacy
Parents who are taught strategies for managing their autistic infant’s sensory challenges report decreased stress and greater confidence in handling reactivity. Reduced parental distress promotes better family quality of life.
Communication Growth
Autistic infants receiving occupational therapy for sensory regulation show greater growth in communication skills like babbling and turn taking compared to autistic infants receiving standard interventions alone.
Need for More Research
While preliminary studies are encouraging, substantially more controlled research on outcomes of early reactivity interventions for autistic infants is needed. Long-term follow-up into the toddler and preschool years is crucial to determine lasting impacts on sensory, social, and language development.
Conclusion
In summary, research indicates autistic infants do tend to react more strongly and aversely to loud noises compared to typical peers, with symptoms detectable as early as 6 months of age. However, there remains considerable individual variability in reactivity across the autism spectrum. Multidisciplinary assessment and individualized accommodations and supports focused on building regulation skills are key to improving developmental trajectories for autistic babies with auditory hypersensitivities. With improved understanding of early sensory experiences in ASD, clinicians will be better equipped to partner with families to foster healthy regulation and engagement from the start. There is much more exciting work to be done elucidating sensory processing differences in infancy that can transform long-term outcomes for autistic individuals.
| Age Range | Key Features of Reactivity |
|---|---|
| 0-3 months | Limited differences detected |
| 3-6 months | Possible subtle processing differences seen in brain activity |
| 6-12 months | Clear symptoms like startles, distress behaviors, and poor habituation noticeable |