Mechanisms of Timing and Temporal Processing (Funded by NSF Grant#: BCS 0818271)
Neural mechanisms for assessing the temporal characteristics of events on a hundreds-of-milliseconds to seconds time scale are fundamental to human perception and performance. On this time scale, research supports at least two distinct mechanisms: an interval-based (‘stopwatch’) mechanism that records, stores and compares durations and a beat-based (‘entrainment’) mechanism that assesses the relative timing of events with respect to an internally-generated periodicity. One topic that has received relatively little research attention is the issue of individual differences. This project considers the possibility that individuals engage in beat-based and interval-based timing, but do so to different degrees. The general project aim is to identify and characterize factors mediating engagement of beat-based and interval-based timing mechanisms. Three lines of research combine a novel sequence-timing paradigm that demonstrates robust individual differences, with a mathematical model that indexes the degree to which performance reflects beat-based judgments. Critical to the sequence-timing paradigm are stimulus sequences that yield opposite perceptions about sequence rate (‘speeding up’ versus ‘slowing down’) depending on whether individuals engage in beat-based or interval-based timing, respectively. The first line examines stimulus characteristics mediating beat-based timing. The second line assesses flexibility in timing mode, focusing on attention and task factors. The third line addresses developmental and training factors. A key contribution of the proposed modeling work is that it integrates two contrasting theories of timing within a single framework. Using this framework to clarify the degree to which individuals engage in beat-based timing improves current limited understanding of individual differences in timing behavior and helps better characterize temporal processing deficits linked to neurological disorders. (Devin McAuley)

Neural Correlates of Individual Differences in Rhythm Perception (Funded by the GRAMMY Foundation)
When people listen to music, they often respond to the rhythm by moving their body in time with the ‘beat’. However, does the ‘beat go on’ for everyone? There are numerous anecdotal reports that some individuals have difficulty perceiving a beat, but there has been very little research on this topic. Through funding from the GRAMMY foundation, we have been able to address this question by combining functional neuroimaging methods with a behavioral paradigm that is diagnostic of individual differences in beat perception. In the first year of the project, we’ve identified brain regions that are activated more strongly in individuals who readily pick up on an implied beat compared with those who do not (see Figure 1). Brain activity in auditory and motor areas is correlated with individual differences in beat perception, even when no behavioral differences are apparent. The current results support two conclusions. First, beat perception is mediated by motor timing circuits involved in performance. Second, some individuals more readily engage these beat-based circuits when judging the timing of music than do others. (Devin McAuley)

Figure 1

Maternal Speech to Infants with and without Hearing Loss (Funded by NIH-NIDCD R01 #DC008581)
Very little is known about the linguistic development of language in infants with hearing loss, particularly infants with cochlear implants. For normal-hearing children, the quality of maternal speech input has been shown to play a role in language development. Many questions remain about the nature of speech input received by children and how it shapes the development of linguistic competency by children. In an NIH/NIDCD-funded research project, we are actively investigating how acoustic, phonetic, and prosodic properties of maternal speech influence the development of speech and language skills in infants with hearing loss and normal-hearing infants. (Laura Dilley and Devin McAuley)

The role of prosody in word segmentation and lexical activation (Funded by BGSU)
Two complementary lines of research explore the role of prosody (pitch and timing cues) in understanding speech. The first investigates the role of prosodic context in word segmentation, i.e., how listeners parse spoken words from continuous speech. The second line of research investigates the role of speech rate and duration in perception of function words and other reduced syllables. These findings have implications for understanding how humans are able to decode the speech signal. (Laura Dilley and Devin McAuley)

Cognitive and phonological representation of prosodic cues
Another line of research concerns the processing and representation of prosodic cues, particularly speech intonation. The pitch patterns that are used in speech contain important information about meaning; how is it that listeners extract this pitch information and interpret it as meaningful propositions? Moreover, to what extent does the tonal representation of speech involve the same set of basic mechanisms as tonal representation in music? (Laura Dilley)

Acoustic-phonetic variability
Normal speech within and across talkers is highly variable acoustically, but it is not known how listeners are able to overcome this acoustic variability in order to understand speech so successfully. This research characterizes what sorts of variability listeners must deal with in speech, and investigates how they are able to perceive words with remarkable accuracy in spite of the variability in acoustic forms. (Laura Dilley)