Lori L Holt

Carnegie Mellon University | CMU · Center for the Neural Basis of Cognition

Humans generate categories from complex regularities evolving across even imperfect sensory input. Here, we examined the possibility that incidental experiences can generate lasting category knowledge. Adults practiced a simple visuomotor task not dependent on acoustic input. Novel categories of acoustically complex sounds were not necessary for ta...

Categorization has a deep impact on behavior, but whether category learning is served by a single system or multiple systems remains debated. Here, we designed two well-equated nonspeech auditory category learning challenges to draw on putative procedural (information-integration) versus declarative (rule-based) learning systems among adult Hebrew-...

Speech perception presents an exemplary model of how neurobiological systems flexibly adjust when input departs from the norm. Dialects, accents, and even head colds can negatively impact comprehension by shifting speech from listeners’ expectations. Comprehension improves with exposure to shifted speech regularities, but there is no neurobiologica...

The environment provides multiple regularities that might be useful in guiding behavior if one was able to learn their structure. Understanding statistical learning across simultaneous regularities is important, but poorly understood. We investigate learning across two domains: visuomotor sequence learning through the serial reaction time (SRT) tas...

In bilingual communities, distinct languages may vie for attention in multitalker conversations. But we do not yet have a detailed understanding of selective attention with the ‘bilingual cocktail party’ with which to develop appropriate and effective clinical and educational interventions. Here we develop a new assay of selective attention to comp...

Multiple lines of research have developed training approaches that foster category learning, with important translational implications for education. Increasing exemplar variability, blocking, or interleaving by category-relevant dimension, and providing explicit instructions about diagnostic dimensions each have been shown to facilitate category l...

No PDF available ABSTRACT In everyday situations, listeners may selectively attend to acoustic dimensions (e.g., frequency) within complex sounds and ignore other simultaneous dimensions. Speech sound categories are defined over multiple dimensions that vary in informativeness; thus, speech perception may demand selective attention to diagnostic di...

No PDF available ABSTRACT Listeners build up statistically driven expectations of what they will hear; however, there is no consensus on how these statistics influence perception, attention, and behavior. Here, we manipulate two statistical properties: global probability (the likelihood of single ‘sound events’) and predictiveness (how often does o...

Most human auditory psychophysics research has historically been conducted in carefully controlled environments with calibrated audio equipment, and over potentially hours of repetitive testing with expert listeners. Here, we operationally define such conditions as having high 'auditory hygiene'. From this perspective, conducting auditory psychophy...

Categorization has a deep impact on behavior, but whether category learning is served by a single or multiple systems remains debated. Here, we designed two well-equated nonspeech auditory category learning challenges to draw upon putative procedural (information-integration) versus declarative (rule-based) learning systems among adult control part...

Unfamiliar accents can systematically shift speech acoustics away from community norms and reduce comprehension. Yet, limited exposure improves comprehension. This perceptual adaptation indicates that the mapping from acoustics to speech representations is dynamic, rather than fixed. But, what drives adjustments is debated. Supervised learning acco...

Humans generate categories from complex regularities present in recurring instances of even imperfect sensory input. Here, we examined the possibility that incidental experiences can generate lasting category knowledge. Adults practiced a simple visuomotor task not dependent on acoustic input. Novel categories of acoustically complex sounds aligned...

Categories are often structured by the similarities of instances within the category defined across dimensions or features. Researchers typically assume that there is a direct, linear relationship between the physical input dimensions across which category exemplars are defined and the psychological representation of these dimensions. However, this...

Cognitive systems face a constant tension of maintaining existing representations that have been fine-tuned to long-term input regularities and adapting representations to meet the needs of short-term input that may deviate from long-term norms. Systems must balance the stability of long-term representations with plasticity to accommodate novel con...

The environment provides multiple regularities that might be useful in guiding behavior if one can learn their structure. Understanding statistical learning across simultaneous regularities is important, but poorly understood. We investigate learning across two domains: motor sequence learning through the serial reaction time (SRT) task and inciden...

Category learning is fundamental to cognition, but little is known about how it proceeds in real-world environments when learners do not have instructions to search for category-relevant information, do not make overt category decisions, and do not experience direct feedback. Prior research demonstrates that listeners can acquire task-irrelevant au...

Speaking precisely is important for effective verbal communication, and articulatory gain is one component of speech motor control that contributes to achieving this goal. Given that the basal ganglia have been proposed to regulate the speed and size of limb movement, that is, movement gain, we explored the basal ganglia contribution to articulator...

Most human auditory psychophysics research has been conducted with extreme 'auditory hygiene' in carefully controlled environments, with calibrated audio equipment, and potentially hours of repetitive testing with expert listeners. The incompatibility of web-based platforms with such experimental regimes would seem to preclude online auditory psych...

Many language functions are traditionally assigned to cortical brain areas, leaving the contributions of subcortical structures to language processing largely unspecified. The present study examines a potential role of the subthalamic nucleus (STN) in lexical processing, specifically, reading aloud of words (e.g., 'fate') and pseudowords (e.g., 'fa...

Cognitive systems face a tension between stability and plasticity. The maintenance of long‐term representations that reflect the global regularities of the environment is often at odds with pressure to flexibly adjust to short‐term input regularities that may deviate from the norm. This tension is abundantly clear in speech communication when talke...

The ability to form coherent acoustic categories is thought to be a fundamental cognitive process underlying speech perception. Auditory categories can be learned via passive exposure or overt training. Recent investigations have shown that listeners can learn categories incidentally based on associations between sounds, visual objects, actions, an...

Research suggests that the auditory system rapidly and efficiently encodes statistical structure of acoustic information through passive exposure. We investigated how exposure to short-term acoustic regularities may change representations and categorization behavior in humans. In Experiment 1, we found that passive exposure to a correlation between...

Categories are often structured by the similarities of instances within the category. A popular dual systems theory of category learning argues that the structure of exemplars forming categories determines the mechanisms that drive learning. Category distributions are necessarily defined by dimensions or features. Researchers typically assume that...

Speech is notoriously variable, with no simple mapping from acoustics to linguistically-meaningful units like words and phonemes. Empirical research on this theoretically central issue establishes at least two classes of perceptual phenomena that accommodate acoustic variability: normalization and perceptual learning. Intriguingly, perceptual learn...

Objective Acoustic distortions to the speech signal impair spoken language recognition, but healthy listeners exhibit adaptive plasticity consistent with rapid adjustments in how the distorted speech input maps to speech representations, perhaps through engagement of supervised error-driven learning. This puts adaptive plasticity in speech percepti...

Recent research demonstrates that the diagnosticity of an acoustic dimension for speech categorization is relative to its relationship to the evolving distribution of dimensional regularity across time, and not simply to its fixed value along the dimension. Two studies examine the nature of this dimension-based statistical learning in online word r...

Adults outperform children on category learning that requires selective attention to individual dimensions (rule-based categories) due to their more highly developed working memory abilities, but much less is known about developmental differences in learning categories that require integration across multiple dimensions (information-integration cat...

Significance Humans are born as “universal listeners.” However, over the first year, infants’ perception is shaped by native speech categories. How do these categories naturally emerge without explicit training or overt feedback? Using fMRI, we examined the neural basis of incidental sound category learning as participants played a videogame in whi...

Human category learning appears to be supported by dual learning systems. Previous research indicates the engagement of distinct neural systems in learning categories that require selective attention to dimensions versus those that require integration across dimensions. This evidence has largely come from studies of learning across perceptually sep...

The sensorimotor cortex is somatotopically organized to represent the vocal tract articulators, such as lips, tongue, larynx, and jaw. How speech and articulatory features are encoded at the subcortical level, however, remains largely unknown. We analyzed local field potential (LFP) recordings from the subthalamic nucleus (STN) and simultaneous ele...

The sensorimotor cortex is somatotopically organized to represent the vocal tract articulators, such as lips, tongue, larynx, and jaw. How speech and articulatory features are encoded at the subcortical level, however, remains largely unknown. We analyzed local field potential (LFP) recordings from the subthalamic nucleus (STN) and simultaneous ele...

Human category learning appears to be supported by dual learning systems. Previous research indicates the engagement of distinct neural systems in learning categories that require selective attention to dimensions versus those that require integration across dimensions. This evidence has largely come from studies of learning across perceptually sep...

Categorization is a critical component of cognition and contributes to many complex processes, including speech perception. High variability within the environment is thought to initially slow learning while increasing the ability to generalize to novel exemplars. However, little is understood about the mechanisms driving this benefit of variabilit...

Adults outperform children on category learning that requires selective attention to individual dimensions (rule-based categories) due to their more highly developed working memory abilities, but much less is known about developmental differences in learning categories that require integration across multiple dimensions (information-integration cat...

There is substantial evidence that two distinct learning systems are engaged in category learning. One is principally engaged when learning requires selective attention to a single dimension (rule-based), and the other is drawn online by categories requiring integration across two or more dimensions (information-integration). This distinction has l...

The contribution of acoustic dimensions to an auditory percept is dynamically adjusted and reweighted based on prior experience about how informative these dimensions are across the long-term and short-term environment. This is especially evident in speech perception, where listeners differentially weight information across multiple acoustic dimens...

Developmental dyslexia is presumed to arise from phonological impairments. Accordingly, people with dyslexia show speech perception deficits taken as indication of impoverished phonological representations. However, the nature of speech perception deficits in those with dyslexia remains elusive. Specifically, there is no agreement as to whether spe...

Basal ganglia-thalamocortical loops mediate all motor behavior, yet little detail is known about the role of basal ganglia nuclei in speech production. Using intracranial recording during deep brain stimulation surgery in humans with Parkinson's disease, we tested the hypothesis that the firing rate of subthalamic nucleus neurons is modulated in sy...

Speech learning involves discovering appropriate functional speech units (e.g., speech categories) embedded in a continuous stream of speech. However, speech category learning has been mostly investigated with isolated sound tokens. Here, we used a videogame to encourage incidental learning of speech categories from continuous speech input (Lim et...

Basal ganglia-thalamocortical loops mediate all motor behavior, yet little detail is known about the role of basal ganglia nuclei in speech production. Using intracranial recording during deep brain stimulation surgery, we tested the hypothesis that the firing rate of subthalamic nucleus neurons is modulated in response to both planning and motor e...

Auditory selective attention is vital in natural soundscapes. But it is unclear how attentional focus on the primary dimension of auditory representation—acoustic frequency—might modulate basic auditory functional topography during active listening. In contrast to visual selective attention, which is supported by motor-mediated optimization of inpu...

Auditory selective attention is vital in natural soundscapes. But, it is unclear how attentional focus on the primary dimension of auditory representation - acoustic frequency - might modulate basic auditory functional topography during active listening. In contrast to visual selective attention, which is supported by motor-mediated optimization of...

The dual systems theory of category learning posits that category distributions requiring selective attention to a single dimension and those requiring integration across dimensions engage distinct neural systems. Our goal was to examine the influence of the dimensions defining categories on learning. Participants trained with feedback to learn aud...

Listeners rapidly reweight the mapping of acoustic cues to speech categories in response to abrupt introductions of accented speech. For instance, when encountering an accent that reverses the typical correlation of acoustic cues to speech category membership, listeners rapidly down-weight reliance on secondary cues [Idemaru and Holt, 2011; 2014; L...

When listeners encounter speech under adverse listening conditions, adaptive adjustments in perception can improve comprehension over time. In some cases, these adaptive changes require the presence of external information that disambiguates the distorted speech signals, whereas in other cases mere exposure is sufficient. Both external (e.g., writt...

Research in visual category learning has identified two distinct neural systems. An explicit system learns rule-based stimulus distributions via explicit testing of rules and strategies. The implicit system, in contrast, learns information-integration stimulus distributions via a slower procedural-learning process. This distinction has recently bee...

Understanding auditory category learning informs the mechanisms available to phonetic category acquisition. Recent research has examined the ability of participants to learn complex, nonspeech auditory categories (Gabay, Dick, Zevin & Holt, 2015) and non-native Mandarin tone categories (Liu, 2014) during incidental training that involves auditory s...

Speech perception depends on long-term representations that reflect regularities of the native language. However, listeners rapidly adapt when speech acoustics deviate from these regularities due to talker idiosyncrasies such as foreign accents and dialects. To better understand these dual aspects of speech perception, we probe native English liste...

Very little is known about how auditory categories are learned incidentally, without instructions to search for category-diagnostic dimensions, overt category decisions, or experimenter-provided feedback. This is an important gap because learning in the natural environment does not arise from explicit feedback and there is evidence that the learnin...

Language learning requires that listeners discover acoustically variable functional units like phonetic categories and words from an unfamiliar, continuous acoustic stream. Although many category learning studies have examined how listeners learn to generalize across the acoustic variability inherent in the signals that convey the functional units...

Research in visual category learning supports the existence of dual category-learning systems with distinct neurobiological substrates. Rule-based category learning is engaged by category input distributions that vary orthogonally in perceptual space whereas information integration learning is engaged when categories are defined across multiple inp...

Developmental dyslexia (DD) is commonly thought to arise from phonological impairments. However, an emerging perspective is that a more general procedural learning deficit, not specific to phonological processing, may underlie DD. The current study examined whether individuals with DD are capable of extracting statistical regularities across sequen...

Adults learn many new tasks with ease, but acquiring the sounds of a new language is notoriously difficult. Decades of attempts to develop effective training regimens have focused primarily on highly explicit approaches to training adults to categorize non-native speech sounds. Participants are aware of the phonetic distinctions they are learning,...

Listeners rapidly reweight the mapping of acoustic cues to speech categories in response to local changes in short-term input [Idemaru & Holt, 2011]. For instance, when encountering an accent that reverses the typical correlation of acoustic cues to speech category membership. Here, we examined the level at which this rapid learning occurs. Listene...

Very little is known about how auditory categories are learned incidentally, without instructions to search for category-diagnostic dimensions, overt category decisions, or experimenter-provided feedback. This is an important gap because learning in the natural environment does not arise from explicit feedback and there is evidence that the learnin...

Objective: Developmental dyslexia is presumed to arise from specific phonological impairments. However, an emerging theoretical framework suggests that phonological impairments may be symptoms stemming from an underlying dysfunction of procedural learning. Method: We tested procedural learning in adults with dyslexia (n = 15) and matched-control...

Listeners must accomplish two complementary perceptual feats in extracting a message from speech. They must discriminate linguistically-relevant acoustic variability and generalize across irrelevant variability. Said another way, they must categorize speech. Since the mapping of acoustic variability is language-specific, these categories must be le...

Listeners use lexical or visual context information to recalibrate auditory speech perception. After hearing an ambiguous auditory stimulus between /aba/ and /ada/ coupled with a clear visual stimulus (e.g., lip closure in /aba/), an ambiguous auditory-only stimulus is perceived in line with the previously seen visual stimulus. What remains unclear...

Speech is commonly claimed to relate to mirror neurons because of the alluring surface analogy of mirror neurons to the Motor Theory of speech perception, which posits that perception and production draw upon common motor-articulatory representations. We argue that the analogy fails and highlight examples of systems-level developmental approaches t...

Human speech perception rapidly adapts to maintain comprehension under adverse listening conditions. For example, with exposure listeners can adapt to heavily accented speech produced by a non-native speaker. Outside the domain of speech perception, adaptive changes in sensory and motor processing have been attributed to cerebellar functions. The p...

Adult speech perception reflects the long-term regularities of the native language, but it is also flexible such that it accommodates and adapts to adverse listening conditions and short-term deviations from native-language norms. The purpose of this article is to examine how the broader neuroscience literature can inform and advance research effor...

Speech perception flexibly adapts to short-term regularities of ambient speech input. Recent research demonstrates that the function of an acoustic dimension for speech categorization at a given time is relative to its relationship to the evolving distribution of dimensional regularity across time, and not simply to a fixed value along the dimensio...

Listeners use lexical knowledge to retune phoneme categories. When hearing an ambiguous sound between /s/ and /f/ in lexically unambiguous contexts such as gira[s/f], listeners learn to interpret the sound as /f/ because gira[f] is a real word and gira[s] is not. Later, they apply this learning even in lexically ambiguous contexts (perceiving knife...

Cognitive neuroscientists studying sound and speech learning have successfully used videogames as a research vehicle. Neuroscientists and game developers worked together to produce a game built to entice participants to longer periods of play, while enabling researchers to easily configure presentation parameters in support of future studies. A spa...

The English /l-r/ distinction is difficult to learn for some second language learners as well as for native-speaking children. This study examines the use of the second (F2) and third (F3) formants in the production and perception of /l/ and /r/ sounds in 4-, 4.5-, 5.5-, and 8.5-yr-old English-speaking children. The children were tested with elicit...

Speech categories are defined by multiple acoustic dimensions, and listeners give differential weighting to dimensions in phonetic categorization. The informativeness (predictive strength) of dimensions for categorization is considered an important factor in determining perceptual weighting. However, it is unknown how the perceptual system weighs a...

Phonetic categorization is influenced by multiple sources of contextual information, but little is known about how different sources of information interact. We examined the relative influence of lexical versus acoustic contexts on phonetic categorization of sounds along [s]-[S] continua embedded in word-nonword pairs (e.g., a[S]amed-a[s]amed, ca[s...

Listeners adapt to non-canonically produced speech by using lexical knowledge to retune phoneme categories. It is unclear, however, whether these retuned categories affect perception at the category level or the signal-to-representation mapping. This was addressed by exploring conditions of cross-speaker generalization of retuned fricatives. During...

Voices have unique acoustic signatures, contributing to the acoustic variability listeners must contend with in perceiving speech, and it has long been proposed that listeners normalize speech perception to information extracted from a talker's speech. Initial attempts to explain talker normalization relied on extraction of articulatory referents,...

Though improvement is evident, in no case is final performance native English-like. We focused our training on the third formant onset frequency, shown to be the most reliable indicator of /r-l/ category membership. We first presented listeners with instances of synthetic /r-l/ stimuli varying only in F3 onset frequency, in a forced-choice identifi...

Many attempts have been made to teach native Japanese listeners to perceptually differentiate English/r-l/(e.g. rock-lock). Though improvement is evident, in no case is final performance native English-like. We focused our training on the third formant onset frequency, shown to be the most reliable indicator of/r-l/category membership. We first pre...

Perceptual aftereffects have been referred to as "the psychologist's microelectrode" because they can expose dimensions of representation through the residual effect of a context stimulus upon perception of a subsequent target. The present study uses such context-dependence to examine the dimensions of representation involved in a classic demonstra...

Speech processing requires sensitivity to long-term regularities of the native language yet demands listeners to flexibly adapt to perturbations that arise from talker idiosyncrasies such as nonnative accent. The present experiments investigate whether listeners exhibit dimension-based statistical learning of correlations between acoustic dimension...