The time of our lives: life span development of timing and event tracking

Life span developmental profiles were constructed for 305 participants (ages 4-95) for a battery of paced and unpaced perceptual-motor timing tasks that included synchronize-continue tapping at a wide range of target event rates. Two life span hypotheses, derived from an entrainment theory of timing and event tracking, were tested. A preferred period hypothesis predicted a monotonic slowing of a preferred rate (tempo) of event tracking across the life span. An entrainment region hypothesis predicted a quadratic profile in the range of event rates that produced effective timing across the life span; specifically, age-specific entrainment regions should be narrower in childhood and late adulthood than in midlife. Findings across tasks provide converging support for both hypotheses. Implications of these findings are discussed for understanding critical periods in development and age-related slowing of event timing.     

Distal rhythm influences whether or not listeners hear a word in continuous speech: Support for a perceptual grouping hypothesis

Due to extensive variability in the phonetic realizations of words, there may be few or no proximal spectro-temporal cues that identify a word’s onset or even its presence. Dilley and Pitt (2010) showed that the rate of context speech, distal from a to-be-recognized word, can have a sizeable effect on whether or not a word is perceived. This investigation considered whether there is a distinct role for distal rhythm in the disappearing word effect. Listeners heard sentences that had a grammatical interpretation with or without a critical function word (FW) and transcribed what they heard (e.g., are in Jill got quite mad when she heard there are birds can be removed and Jill got quite mad when she heard their birds is still grammatical). Consistent with a perceptual grouping hypothesis, participants were more likely to report critical FWs when distal rhythm (repeating ternary or binary pitch patterns) matched the rhythm in the FW-containing region than when it did not. Notably, effects of distal rhythm and distal rate were additive. Results demonstrate a novel effect of distal rhythm on the amount of lexical material listeners hear, highlighting the importance of distal timing information and providing new constraints for models of spoken word recognition.     

Altering the rhythm of target and background talkers differentially affects speech understanding

Three experiments investigated listeners’ ability to use speech rhythm to attend selectively to a single target talker presented in multi-talker babble (Experiments 1 and 2) and in speech-shaped noise (Experiment 3). Participants listened to spoken sentences of the form “Ready [Call sign] go to [Color] [Number] now” and reported the Color and Number spoken by a target talker (cued by the Call sign “Baron”). Experiment 1 altered the natural rhythm of the target talker and background talkers for two-talker and six-talker backgrounds. Experiment 2 considered parametric rhythm alterations over a wider range, altering the rhythm of either the target or the background talkers. Experiments 1 and 2 revealed that altering the rhythm of the target talker, while keeping the rhythm of the background intact, reduced listeners’ ability to report the Color and Number spoken by the target talker. Conversely, altering the rhythm of the background talkers, while keeping the target rhythm intact, improved listeners ability to report the Color and Number spoken by the target talker. Experiment 3, which embedded the target talker in speech-shaped noise rather than multi-talker babble, similarly reduced recognition of the target sentence with increased alteration of the target rhythm. This pattern of results favors a dynamic-attending theory-based selective-entrainment hypothesis over a disparity-based segregation hypothesis and an increased salience hypothesis.