Listening to language at birth: evidence for a bias for speech in neonates

The nature and origin of the human capacity for acquiring language is not yet fully understood. Here we uncover early roots of this capacity by demonstrating that humans are born with a preference for listening to speech. Human neonates adjusted their high amplitude sucking to preferentially listen to speech, compared with complex non-speech analogues that controlled for critical spectral and temporal parameters of speech. These results support the hypothesis that human infants begin language acquisition with a bias for listening to speech. The implications of these results for language and communication development are discussed. For a commentary on this article see Rosen and Iverson (2007).     

Qualitative attentional changes with age in doing two tasks at once

Does practice reduce, or even eliminate, aging effects on the attentional limitations responsible for dual-task interference? The studies reviewed in this article show that age differences reliably persist after extensive practice. Strikingly, dual-task interference remains larger among older adults even in training conditions that allow them to achieve single-task performance as fast as younger adults. These findings demonstrate that age deficits in attentional functioning are robust. Advancing age also can be accompanied by improvements in cognitive functioning, such as in the ability to access the lexicon without attention (i.e., automatically), due to lifelong experience with word reading. Future research needs to establish whether age deficits in central attention are due to structural changes that are irreversible or reversible to some extent.     

Doing two things at once: The role of temporal compatibility

Performance in a periodically repeating keypress response was measured as a function of the relation between the response patterns required of the two hands. Compared to identical left- and right-hand responses, performance was degraded when the temporal periods of the left- and right-hand responses were not harmonically related. By contrast, performance was not degraded compared to the identical task control when the left- and right-hand responses had the same or harmonically related periods. These findings suggest a limitation in parallel generation of multiple time frames that is assumed to be associated with a late stage of central processing in which response commands are generated.     

Attending to forty-nine spatial positions at once.

Simultaneous attention to 49 spatial positions resulted in the processing of threshold information from one of those positions essentially identical to the processing when the subject knew in advance that that position would be tested. This result held true when the task consisted of detection of the presence of a briefly presented dot. The same result held true for 9 spatial positions when the task consisted of report of the briefly presented letter in the target position.     

Listening with eye and hand: cross-modal contributions to speech perception.

Three experiments investigated the "McGurk effect" whereby optically specified syllables experienced synchronously with acoustically specified syllables integrate in perception to determine a listener's auditory perceptual experience. Experiments contrasted the cross-modal effect of orthographic on acoustic syllables presumed to be associated in experience and memory with that of haptically experienced and acoustic syllables presumed not to be associated. The latter pairing gave rise to cross-modal influences when Ss were informed that cross-modal syllables were paired independently. Mouthed syllables affected reports of simultaneously heard syllables (and vice versa). These effects were absent when syllables were simultaneously seen (spelled) and heard. The McGurk effect does not arise from association in memory but from conjoint near specification of the same causal source in the environment--in speech, the moving vocal tract producing phonetic gestures.     

The costs of doing two things at once for young and older adults: talking while walking,finger tapping,and ignoring speech or noise

Young and older adults provided language samples in response to questions while walking, finger tapping, and ignoring speech or noise. The language samples were scored on 3 dimensions: fluency, complexity, and content. The hypothesis that working memory limitations affect speech production by older adults was tested by comparing baseline samples with those produced while the participants were performing the concurrent tasks. There were baseline differences: Older adults' speech was less fluent and less complex than young adults' speech. Young adults adopted a different strategy in response to the dual-task demands than older adults: They reduced sentence length and grammatical complexity. In contrast, older adults shifted to a reduced speech rate in the dual-task conditions.     

On doing two things at once: Temporal constraints on actions in language comprehension

In two experiments, we investigated how text comprehension is influenced by the interaction between the properties of actions and the temporal relations specified by adverbs. Participants read short narratives describing a protagonist who performed two actions that involved similar sensorimotor systems (e.g., chopping wood and painting a fence) or different ones (e.g., whistling a melody and painting a fence). The actions were described as simultaneous or successive by means of the temporal adverbs while and after, respectively. Comprehension, both in Spanish and in English, was markedly impaired (longer reading times and lower subjective coherence) for sentences including the adverb while and actions involving the same sensorimotor system. However, when one of the same sensorimotor system actions was described as a mental plan (e.g., chopping wood and thinking of painting a fence), comprehension was equally easy with the adverbs while and after. These results are compatible with a revised version of the indexical hypothesis that specifies how comprehension is guided by syntax and embodied constraints within multiple noninteracting mental spaces.     

Revealing language deficits following stroke: the cost of doing two things at once

The costs of doing two things were assessed for a group of healthy older adults and older adults who were tested at least 6 months after a stroke. A baseline language sample was compared to language samples collected while the participants were performing concurrent motor tasks or selective ignoring tasks. Whereas the healthy older adults showed few costs due to the concurrent task demands, the language samples from the stroke survivors were disrupted by the demands of doing two things at once. The dual task measures reveal long-lasting effects of strokes that were not evident when stroke survivors were assessed using standard clinical tools.     

Interfering with memory for faces: The cost of doing two things at once

We inferred the processes critical for episodic retrieval of faces by measuring susceptibility to memory interference from different distracting tasks. Experiment 1 examined recognition of studied faces under full attention (FA) or each of two divided attention (DA) conditions requiring concurrent decisions to auditorily presented letters. Memory was disrupted in both DA relative to FA conditions, a result contrary to a material-specific account of interference effects. Experiment 2 investigated whether the magnitude of interference depended on competition between concurrent tasks for common processing resources. Studied faces were presented either upright (configurally processed) or inverted (featurally processed). Recognition was completed under FA, or DA with one of two face-based distracting tasks requiring either featural or configural processing. We found an interaction: memory for upright faces was lower under DA when the distracting task required configural than featural processing, while the reverse was true for memory of inverted faces. Across experiments, the magnitude of memory interference was similar (a 19% or 20% decline from FA) regardless of whether the materials in the distracting task overlapped with the to-be-remembered information. Importantly, interference was significantly larger (42%) when the processing demands of the distracting and target retrieval task overlapped, suggesting a processing-specific account of memory interference.     

Speaking two languages at once: Unconscious native word form access in second language production

Bilingualism research has established language non-selective lexical access in comprehension. However, the evidence for such an effect in production remains sparse and its neural time-course has not yet been investigated. We demonstrate that German-English bilinguals performing a simple picture-naming task exclusively in English spontaneously access the phonological form of –unproduced– German words. Participants were asked to produce English adjective-noun sequences describing the colour and identity of familiar objects presented as line drawings. We associated adjective and picture names such that their onsets phonologically overlapped in English (e.g., green goat), in German through translation (e.g., blue flower – ‘blaue Blume’), or in neither language. As expected, phonological priming in English modulated event-related brain potentials over the frontocentral scalp region from around 440 ms after picture onset. Phonological priming in German was detectable even earlier, from 300 ms, even though German was never produced and in the absence of an interaction between language and phonological repetition priming at any point in time. Overall, these results establish the existence of non-selective access to phonological representations of the two languages in the domain of speech production.     

Listening rate and comprehension as a function of preference for and exposure to time-altered speech

We conducted experiments on the effects of brief prior exposure to time-altered speech on preferred listening rate and the rate listeners would select when asked to listen to speech as fast as possible with good compression (induced listening rate). In Exp. 1, 48 participants were exposed either to normal rate speech or to speech compressed to twice-normal rate. Brief exposure to twice-normal rate speech led to a faster induced listening rate than exposure to normal rate speech. In Exp. 2, 31 participants were briefly exposed to normal rate speech, speech compressed to twice-normal rate, or speech expanded to half-normal rate. The faster the rate of the exposure speech, the faster the induced rate. Speech compressed to twice-normal rate led to a faster induced listening rate than exposure to speech expanded to half-normal rate. Normal rate speech was intermediate between twice-normal and half-normal rate and did not differ significantly from them. Induced listening rate was a linear combination of listening rate preference and recent forced exposure to time-altered speech.     

Searching for two things at once: Evidence of exclusivity in semantic and autobiographical memory retrieval

We examined whether retrieval from semantic memory (Experiment 1) and autobiographical memory (Experiment 2) is exclusive, or whether people can search for two things at once. In Experiment 1, participants retrieved items as quickly as possible over 4 ruin from single categories (e.g., foods, countries) and from disjunctive categories (e.g., foods or countries). In Experiment 2, participants retrieved autobiographical episodes associated with single cue words (e.g., flower, ticket) or with disjunctive cue words (e.g., flower or ticket). In both experiments, retrieval of items from the disjunctive category did not exceed predictions based on optimal sequencing of retrieval from the corresponding two single categories. That is, exclusivity was observed to occur in retrieval from among multiple nonoverlapping categories in both semantic and autobiographical memory.     

Seeing two sides at once: effects of viewpoint and object structure on recognizing three-dimensional objects

Five experiments demonstrated that adults can identify certain novel views of 3-dimensional model objects on the basis of knowledge of a single perspective. Geometrically irregular contour (wire) and surface (clay) objects and geometrically regular surface (pipe) objects were accurately recognized when rotated 180 degrees about the vertical (y) axis. However, recognition accuracy was poor for all types of objects when rotated around the y-axis by 90 degrees. Likewise, more subtle rotations in depth (i.e., 30 degrees and 60 degrees) induced decreases in recognition of both contour and surface objects. These results suggest that accurate recognition of objects rotated in depth by 180 degrees may be achieved through use of information in objects' 2-dimensional bounding contours, the shapes of which remain invariant over flips in depth. Consistent with this interpretation, a final study showed that even slight rotations away from 180 degrees cause precipitous drops in recognition accuracy.     

Searching for two things at once: Establishment of multiple attentional control settings on a trial-by-trial basis

Recent work has demonstrated that attention can be configured to multiple potential targets in spatial search. However, this previous work relied on a fixed set of targets across multiple trials, allowing observers to offload attentional control settings to longer-term representations. In the present experiments, we demonstrate multiple attentional control settings that operate independently of space (Experiments 1 and 2). More important, we show that observers can be cued to different control settings on a trial-by-trial basis (Experiment 3). The latter result suggests that observers were capable of maintaining multiple control settings when the demands of the task required an attentional search for specific feature values. Attention can be configured to extract multiple feature values in a goal-directed manner, and this configuration can be can be dynamically engaged on a trial-by-trial basis. These results support recent findings that reveal the high precision, complexity, and flexibility of attentional control settings.     

Listening for mispronunciations: A measure of what we hear during speech

Ss heard a passage from Lewis Carroll’s Through the Looking Glass and were asked to indicate, as quickly as possible, whenever they heard a mispronunciation. Mispronunciations were produced by changing one consonant sound in a three-syllable word by one, two, or four distinctive features (e.g., busily to “pizily,” “visily,” or “sizily”). Mispronunciations involving a single feature change were seldom detected, while two and four feature changes were readily detected. The syllable in which a mispronunciation occurred did not affect the probability of detecting a mispronunciation. However, reaction times to mispronounced words were at least a third of a second slower when they occurred in the-first syllable of the word. The results were taken to support the notion that words are identified by their distinctive features.