Behavioral Manifestations of Listening Effort
Condition: Listening Effort
Study type: Observational

Summary: 
      The purpose of this investigation is to investigate the behavioral manifestations of
      listening effort. Quantifying listening effort based on an easy to measure behavioral metric
      would allow for better understanding of the effort that goes into processing conversational
      speech. The investigators hypothesize that the behavior modifications required to improve the
      signal to noise ratio in increasingly complex listening environments significantly deviates
      from quiet listening environments. Further, the investigators hypothesize that this directly
      contributes to increased listening effort and reduced ability to accurately monitor content
      for everyday conversation.
    

Detailed description: 
      Listening Effort has been described as a reflection of the cognitive resources necessary for
      speech understanding. Measures can broadly be classified into Subjective, Physiological and
      Behavioral measures of Listening Effort (LE). Subjective measures of LE involve the listener
      rating or answering a questionnaire on the presented auditory stimuli. Some examples of
      Subjective measures are the multidimensional speech, spatial and qualities (SSQ) scale and
      Listening effort rating scale. However, these measures suffer from individual bias, for
      example, what one person might find takes more effort, another might not.

      Physiological measures establish relationships between changes in the central and/or
      autonomic nervous system activity and LE. Effect of LE on central nervous system activity
      include methods such as using Functional Magnetic Resonance Imaging (fMRI) to compare
      processing of noise vocoded versus clear sentence stimuli and using Electroencephalography
      (EEG) to monitor memory/cognitive load. Some methods of measuring effects on Autonomic
      Nervous system are through Pupillometry and Skin Conductance. Research has found that
      fluctuating pupil size may be an indicator of mental task load and/or attention, stress and
      memory. Furthermore, Pupillometric methods have been used to correlate changing measures like
      pupil size and listening tasks. There are some drawbacks of using pupillometry to measure LE-
      Absolute pupil size and change in pupil size for presented speech change according to the age
      of the listener. For instance, Older adults have been found to have smaller absolute pupil
      size and show lesser change in pupil size when moving from difficult to easier listening
      conditions. These drawbacks can be accounted for by normalizing the pupil size.

      Behavioral measures take into account that the there is a decline in cognitive functions over
      prolonged mental effort used an auditory dual task paradigm where the primary task was word
      recognition and the secondary tasks were memory recall and Visual Response times. Apart from
      the Dual tasks, participants were also asked to assign a subjective rating based on SSQ.
      Findings revealed 1) that there is empirical evidence linking repeated instances of effortful
      listening and subsequent cognitive failure and 2) self- report measures did not show the same
      changes as the behavioral measures. It has been suggested that this may indicate that
      subjective (self-report) measures and behavioral measures assess separate aspects of fatigue.
      It may also be due to subjective measures having individual biases.

      As mentioned above, there are numerous studies of subjective, objective and behavioral
      measures of LE, yet, there are no studies of the actual behavior employed by listeners to
      reduce listening effort. Further, researchers do not understand how these behaviors influence
      the ability of the listener to monitor and maintain conversational speech. Listeners must
      rely on both peripheral and central auditory mechanisms to process speech. As the auditory
      signal increases in complexity, likewise there is an increase in the auditory processing
      required to understand speech. The effort that the auditory system must put forth to process
      complex signals is even greater if the signal degraded or imbedded in competing signals such
      as background noise. This requires increased exertion and mental effort on the part of the
      listener, and results in a reduction in ability to maintain focus and an increase in fatigue.
      These issues are further amplified in the presence of a peripheral hearing disorder as
      listeners do not have the mechanisms required to properly process even simple and
      unchallenged auditory signals. Research has demonstrated decreasing word recognition accuracy
      with decreasing Signal to Noise Ratio (SNR) and demonstrated an increase in listening effort
      when speech was presented in increasingly negative SNRs. Numerous studies have reported on
      the increase in listening effort required for individuals with hearing loss.

      The purpose of this investigation is quantify listening effort based subjective, objective
      and behavioral measures at different Signal to Noise Ratios (SNR).
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Subjects will be selected from the University of Miami Ear Institute