Biology Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/2749

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HOW BILINGUALS' COMPREHENSION OF CODE-SWITCHES INFLUENCES ATTENTION AND MEMORY
(2024) Salig, Lauren; Novick, Jared; Slevc, L. Robert; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Bilinguals sometimes code-switch between their shared languages. While psycholinguistics research has focused on the challenges of comprehending code-switches compared to single-language utterances, bilinguals seem unhindered by code-switching in communication, suggesting benefits that offset the costs. I hypothesize that bilinguals orient their attention to speech content after hearing a code-switch because they draw a pragmatic inference about its meaning. This hypothesis is based on the pragmatic meaningfulness of code-switches, which speakers may use to emphasize information, signal their identity, or ease production difficulties, inter alia. By considering how code-switches may benefit listeners, this research attempts to better align our psycholinguistic understanding of code-switch processing with actual bilingual language use, while also inspiring future work to investigate how diverse language contexts may facilitate learning in educational settings. In this dissertation, I share the results of three pre-registered experiments with Spanish-English bilinguals that evaluate how hearing a code-switch affects attention and memory. Experiment 1a shows that code-switches increase bilinguals’ self-reported attention to speech content and improve memory for that information, compared to single-language equivalents. Experiment 1b demonstrates that this effect requires bilingual experience, as English-speaking monolinguals did not demonstrate increased attention upon hearing a code-switch. Experiment 2 attempts to replicate these results and establish the time course of the attentional effect using an EEG measure previously associated with attentional engagement (alpha power). However, I conclude that alpha power was not a valid measure of attention to speech content in this experiment. In Experiment 3, bilinguals again showed better memory for information heard in a code-switched context, with a larger benefit for those with more code-switching experience and when listeners believed the code-switches were natural (as opposed to inserted randomly, removing the element of speaker choice). This suggests that the memory benefit comes from drawing a pragmatic inference, which likely requires prior code-switching experience and a belief in code-switches’ communicative purpose. These experiments establish that bilingual listeners derive attentional and memory benefits from ecologically valid code-switches—challenging a simplistic interpretation of the traditional finding of “costs.” Further, these findings motivate future applied work assessing if/how code-switches might benefit learning in educational contexts.
Knowledge and Processing of Morphosyntactic Variation in African American Language and Mainstream American English
(2023) Maher, Zachary Kevin; Edwards, Jan; Novick, Jared; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
As people from different social groups come into contact, they must accommodate differences in morphosyntax (e.g., He seem nice vs. He seems nice) in order to successfully represent and comprehend their interlocutor’s speech. Listeners usually have high comprehension across such differences, but little is known about the mechanisms behind morphosyntactic accommodation. In this dissertation, I asked what listeners know about variation in morphosyntax and how they deploy this knowledge in real-time language processing. As a test case, I focused on regularized subject-verb agreement (e.g., He seem nice, They was happy)—which is common in African American Language (AAL), but not in Mainstream American English (MAE)—and compared how listeners adjust their linguistic expectations depending on what language varieties both they and their interlocutors speak. In Experiment 1, I showed that participants who primarily speak MAE 1) recognize that some speakers use regularized subject-verb agreement, 2) evaluate that regularized subject-verb agreement is associated with AAL, and 3) predict that the subject-verb agreement rules of AAL allow for some patterns (They was happy) but not others (*He were happy). This was accomplished using a novel sentence rating task, where participants heard audio examples of a given language variety, then rated written sentences for how likely a speaker of that variety would be to say them. In Experiment 2, I showed that a similar pool of participants did not merely recognize regularized subject-verb agreement; their knowledge of variation lead them to predict that AAL speakers use regularized forms in an acoustically ambiguous context. Participants heard sentences like He sit(s) still, where it is unclear whether the verb includes a verbal -s due to a segmentation ambiguity. They were more likely to transcribe a regularized form (He sit still) when it was spoken by an AAL-speaking voice than when it was spoken by an MAE-speaking voice. Together, these results indicate that listeners have rich mental models of their interlocutors that extend beyond a general awareness of linguistic difference. In Experiment 3, I compared bidialectal speakers of AAL and MAE and monodialectal speakers of MAE. On the rating task from Experiment 1, bidialectal participants showed a greater degree of differentiation between sentences that are grammatical in AAL and sentences that are ungrammatical in AAL, compared to monodialectal participants. However, both groups of participants indicated that ungrammatical sentences are broadly more likely in AAL than MAE, contrary to usage patterns in the world. On the transcription task from Experiment 2, bidialectal participants were overall more likely to transcribe regularized subject-verb agreement, but they differentiated between AAL- and MAE-speaking voices to the same degree as monodialectal participants. Both groups were more likely to use MAE subject-verb agreement (He sits still) than regularized subject-verb agreement (He sit still). These results suggest that bidialectal listeners broadly expect regularized subject-verb agreement to a greater degree than do monodialectal listeners, rather than making stronger predictions about a given speaker. Moreover, while bidialectal listeners have a more granular sense of AAL’s grammatical rules, all listeners still favor MAE, likely reflecting MAE’s dominant status. In Experiment 4, I asked how listeners use their knowledge of variation in subject-verb agreement to guide real-time interpretation of sentences, again comparing bidialectal and monodialectal participants. Participants heard sentences like The duck(s) swim in the pond, where they must rely on the agreement morphology of the verb to determine whether the subject of the sentence is singular or plural, since a segmentation ambiguity makes it unclear whether the noun ends in -s. In MAE, only a plural interpretation is available, while in AAL, a singular interpretation is also available. Participants’ eye-movements were tracked as they looked at and selected images on a screen. Participants were more likely to look at and select a singular image if the sentence was presented in an AAL-speaking voice, compared to an MAE-speaking voice, and bidialectal participants were more likely to look at and select a singular image, compared to monodialectal participants. As with the transcription task in Experiment 3, this suggests that bidialectal participants are broadly more likely to consider the possibility that a speaker uses regularized SVA, compared to monodialectal participants, but their linguistic expectations are not more strongly differentiated based on the grammar of their interlocutor. These results make it clear that listeners have mental models of morphosyntactic variation, which can be characterized along a variety of dimensions, including the syntax, semantics, and indexicality (social meaning) of a given variable. This can serve as a foundation for future inquiry into the details of these models and the real-time switching and control dynamics as listeners adjust to different varieties in their environment.
EEG EFFECTS OF EVENT MODELS IN STORY COMPREHENSION
(2023) Rickles, Ben Bogart; Bolger, Donald J; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Cognitive models can offer deep insights into how stories are comprehended. Models which follow event segmentation theory (EST) focus on the processing of brief episodes or events within a narrative and the boundaries between events. To test the brain mechanisms proposed by EST to occur at the event boundaries we looked at electroencephalographs (EEG) recorded from 49 participants as they were tasked with both listening to and recalling 9 blocks of ~ 6 minute-long audio clips in one of three conditions: single ordered stories, unrelated events from unrelated stories, or single stories in scrambled order. All stimuli were designed to contain event boundaries spaced at semi-regular intervals. Accuracy during an inference recognition task administered after each block was highest in the single ordered stories condition. Analysis 1 examined the effects of event boundary vs. local semantic context on evoked negativities (N400) related to lexical processing of each word. Effects of condition suggest that narrative structure affected lexical processing, more so than event-level structure and sentence-level semantic context. Analysis 2 Examined changes in alpha (8.5-12.5 Hz) and theta (4-8 Hz) band power of the EEG induced by the onset of the event boundary. Boundary-induced changes in both frequencies were recorded, in all conditions. The largest increases were recorded during the ordered stories over large portions of the scalp. How these findings relate to cognitive mechanisms suggested by event segmentation theory is discussed.
BRAIN BASIS OF HUMAN SOCIAL INTERACTION: NEUROCOGNITIVE FUNCTIONS AND META-ANALYSIS
(2023) Merchant, Junaid Salim; Redcay, Elizabeth; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Social interactions, or the reciprocal exchange between socially engaged individuals, plays a central role in shaping human life. Social interactions are fundamental for neurocognitive development, and a key factor contributing to mental and physical health. Despite their importance, research investigating the neurocognitive systems associated with human social interaction is relatively new. Human neuroimaging research has traditionally used approaches that separate the individual from social contexts, thereby limiting the ability to examine brain systems underlying interactive social behavior. More recent work has begun incorporating real-time social contexts, and have implicated an extended network of brain regions associated with social interaction. However, open questions remain about the neurocognitive processes that are critical for social interactions and the brain systems that are commonly engaged. The current dissertation aims to address these gaps in our understanding through a set of studies using computational and data-driven approaches. Study 1 examined the relationship between social interaction and mentalizing, which is the ability to infer the mental states of others that is considered to be critically important for social interactions. Prior work has demonstrated that mentalizing and social interaction elicit brain activity spatially overlapping areas, but spatial overlap is not necessarily indicative of a common underlying process. Thus, Study 1 utilized multivariate approaches to examine the similarity of brain activity patterns associated with mentalizing outside of social contexts and when interacting with a peer (regardless of mentalizing) as a means for inferring a functional relationship between the two. Study 2 investigated brain regions commonly engaged across social interactive contexts using coordinate-based meta-analysis, which is an approach for aggregating findings across neuroimaging literature. This involved an exhaustive search strategy to find fMRI and PET studies that utilize social interactive approaches, and calculated spatial convergence across studies as a means to uncover brain regions that are reliably implicated during social interaction. The results from Studies 1 and 2 offer major advancements for a neuroscientific understanding of social interaction by demonstrating a functional link with mentalizing and through elucidating brain systems that are commonly reported in studies using social interactive approaches.
Developmental Parsing and Cognitive Control
(2022) Ovans, Zoe; Huang, Yi Ting; Novick, Jared; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Processing sentences incrementally entails making commitments to structure (and sometimes role assignments) before all information in a sentence is present. Children in particular have been shown to have difficulty revising the initial structural commitments they make when these turn out to be incorrect (Trueswell et al., 1999; Hurewitz et al., 2000; Weighall, 2008; Choi & Trueswell, 2010; Anderson et al., 2011). While prior research has generally ascribed this to limitations in the development of children’s non-linguistic cognitive-control system, a precise account of how cognitive control limitations might lead to difficulty with incremental sentence processing is missing from the literature. In part, this is because existing research has focused on individual differences in children’s ability to exert cognitive control over their thoughts and actions. In contrast, this dissertation makes use of within-child variation in cognitive-control engagement to provide evidence that children’s domain-general cognitive-control system pushes them to rely more heavily on reliable parsing cues (and less heavily on unreliable ones) when the system is highly engaged. This conclusion brings together seemingly disparate results from child and adult conflict adaptation studies, where adults appear to adapt to conflict but children do not. Overall, it is concluded that cognitive-control engagement leads both children and adults to re-rank parsing cues to attend more to ones that are more task-relevant, but the criteria they use to determine which cues are most relevant can change with language experience.
The Role of Cognitive Control in Bilingual Code-Switch Comprehension
(2021) Salig, Lauren; Novick, Jared; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Bilinguals experience a conflict when comprehending a sentence that code-switches from one language to another. However, why bilinguals experience conflict during code-switch comprehension is unclear. This study asks: Does being in a cognitive state conducive to resolving conflict help bilinguals read code-switches faster? If so, it would indicate that comprehending a code-switch involves conflict at an early lexical/syntactic level because faster resolution of the conflict would facilitate faster code-switch reading. 101 Spanish-English bilinguals completed Flanker-arrow trials to manipulate their engagement of cognitive control—which regulates conflict detection and resolution. Immediately after this cognitive-control manipulation, bilinguals read code-switched or unilingual sentences. Having cognitive control engaged prior to encountering a code-switch did not result in faster reading of code-switches. This finding provides preliminary evidence that reading a code-switch may not involve conflict at a lexical/syntactic level. Future work should further investigate the type of conflict that bilinguals encounter during code-switch comprehension.
Rethinking analogical reasoning: The power of stimuli and task framework in understanding biomedical science, technological advancements, and social interactions
(2021) Catanzarite, Nicole Crystal; Bolger, Donald J; Dunbar, Kevin N; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Analogical reasoning is a critical learning process, as it is thought to form the basis of the construction of knowledge and problem solving in novel contexts. To better understand how to leverage this strategy, knowledge of the cognitive mechanisms that underlie reasoning, as well as factors that modulate reasoning, is needed. Such knowledge can springboard the development of communication, presentation, and testing strategies that facilitate accurate comprehension of information. While the benefits of analogical reasoning are clear, researchers continue to debate whether humans are predisposed to reason on a surface level or on a deeper, analogical level. Since analogy can be employed in a variety of contexts, we sought to determine whether the successful engagement of analogy is context-dependent. To understand reasoning in social interactions, we investigated the types of relations individuals identified in situations involving negotiation, conflict, and resolution. These types of situations, described by short, fable-like stories, are a hallmark of classical analogical reasoning research paradigms. To expose applications of reasoning in science and technology (S&T), we explored how different strategies can be used to identify relations between the mechanisms of drug delivery and the defense capabilities of military-operated unmanned aerial vehicles (UAVs). We found that numerous factors can selectively modulate reasoning and that reasoning strategy is situation-dependent. We also found that the way that individuals are probed or tested with targeted questions drives the way in which analogical reasoning is deployed. Consequently, analogical reasoning can be used to facilitate comprehension of technical concepts if asked to retrieve at a deeper conceptual level. Based on these findings, we argue that reasoning is a flexible and strategic process, rather than a fixed ability. As such, this suggests that analogical reasoning can be used to more effectively communicate and present scientific and technical information. Further, the strategic use of analogical reasoning has assessment, training, and strategic messaging applications in countless contexts, such as those within education, vocational training, healthcare, media, and even legal settings.
The use of the domestic dog (Canis familiaris) as a comparative model for speech perception
(2020) Mallikarjun, Amritha; Newman, Rochelle S; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Animals have long been used as comparative models for adult human speech perception. However, few animal models have been used to explore developmental speech perception questions. This dissertation encourages the use of domestic dogs as a behavioral model for speech perception processes. Specifically, dog models are suggested for questions about 1) the role and function of underlying processes responsible for different aspects of speech perception, and 2) the effect of language experience on speech perception processes. Chapters 2, 3, and 4 examined the contributions of auditory, attention, and linguistic processing skills to infants’ difficulties understanding speech in noise. It is not known why infants have more difficulties perceiving speech in noise, especially single-talker noise, than adults. Understanding speech in noise relies on infants’ auditory, attention, and linguistic processes. It is methodologically difficult to isolate these systems’ contributions when testing infants. To tease apart these systems, I compared dogs’ name recognition in nine- and single-talker background noise to that of infants. These studies suggest that attentional processes play a large role in infants’ difficulties in understanding speech in noise. Chapter 5 explored the reasons behind infants’ shift from a preference for vowel information (vowel bias) to consonant information (consonant bias) in word identification. This shift may occur due to language exposure, or possessing a particular lexicon size and structure. To better understand the linguistic exposure necessary for consonant bias development, I tested dogs, who have long-term linguistic exposure and a minimal vocabulary. Dogs demonstrated a vowel bias rather than a consonant bias; this suggests that a small lexicon and regular linguistic exposure, plus mature auditory processing, do not lead to consonant bias emergence. Overall, these chapters suggest that dog models can be useful for broad questions about systems underlying speech perception and about the role of language exposure in the development of certain speech perception processes. However, the studies faced limitations due to a lack of knowledge about dogs’ underlying cognitive systems and linguistic exposure. More fundamental research is necessary to characterize dogs’ linguistic exposure and to understand their auditory, attentional, and linguistic processes to ask more specific comparative research questions.
Development of Motivational Influences on Monitoring and Control Recruitment in the Context of Proactive and Reactive Control in Adolescent Males
(2020) Bowers, Maureen; Fox, Nathan A; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Adolescence and the onset of puberty is a time period of physiological and behavioral changes that include a heightened reward sensitivity, but underdeveloped cognitive control. Cognitive control involves monitoring for salient stimuli and recruiting control to adapt behavior advantageously to reach a specific goal and is supported by the three domains of executive functioning (EF): inhibitory control, set-shifting, and working memory. Proactive control is engaged after an informative cue in preparation for an upcoming stimulus, while reactive control can be employed when preparation is not possible and you need to respond to a stimulus. Oscillations in the theta frequency (4-8Hz) during both cue presentation and stimulus presentation are implicated in proactive and reactive control processes. While reward has been shown to upregulate proactive control in adults, little work has assessed how reward influences theta oscillations during both proactive and reactive control throughout adolescence and pubertal development. Further, no work has sought to understand how EF abilities bolster reward-related changes in proactive or reactive control. Here, 68 adolescent males (Meanage=13.61, SDage=2.52) aged 9 – 17 years old completed a rewarded cued flanker paradigm while electroencephalogram (EEG) was collected. They also completed tasks from the NIH toolbox that tap the three EF domains. Behaviorally, reward hindered performance on proactive trials, particularly in mid-puberty, while enhancing performance on reactive trials. Reward was associated with increases in cue-locked theta power, but with overall reductions in cue-locked theta ICPS. Stim-locked theta power increased on reactive trials with increasing age, while stim-locked theta ICPS peaked in mid-adolescence for rewarded trials. Increased cue theta power was associated with worse performance on proactive trials. On proactive trials, adolescents with low levels of inhibitory control experience more reward-related interference, while reward-related interference was mitigated by better set-shifting abilities only in younger and older adolescents. In conclusion, reward differentially impacts proactive and reactive control throughout adolescent development and EF influences the impact of reward on proactive control throughout adolescence.
THE ACOUSTIC QUALITIES THAT INFLUENCE AUDITORY OBJECT AND EVENT RECOGNITION
(2019) Ogg, Mattson Wallace; Slevc, L. Robert; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Throughout the course of a given day, human listeners encounter an immense variety of sounds in their environment. These are quickly transformed into mental representations of objects and events in the world, which guide more complex cognitive processes and behaviors. Through five experiments in this dissertation, I investigated the rapid formation of auditory object and event representations (i.e., shortly after sound onset) with a particular focus on understanding what acoustic information the auditory system uses to support this recognition process. The first three experiments analyzed behavioral (dissimilarity ratings in Experiment 1; duration-gated identification in Experiment 2) and neural (MEG decoding in Experiment 3) responses to a diverse array of natural sound recordings as a function of the acoustic qualities of the stimuli and their temporal development alongside participants’ concurrently developing responses. The findings from these studies highlight the importance of acoustic qualities related to noisiness, spectral envelope, spectrotemporal change over time, and change in fundamental frequency over time for sound recognition. Two additional studies further tested these results via syntheszied stimuli that explicitly manipulated these acoustic cues, interspersed among a new set of natural sounds. Findings from these acoustic manipulations as well as replications of my previous findings (with new stimuli and tasks) again revealed the importance of aperiodicity, spectral envelope, spectral variability and fundamental frequency in sound-category representations. Moreover, analyses of the synthesized stimuli suggested that aperiodicity is a particularly robust cue for some categories and that speech is difficult to characterize acoustically, at least based on this set of acoustic dimensions and synthesis approach. While the study of the perception of these acoustic cues has a long history, a fuller understanding of how these qualities contribute to natural auditory object recognition in humans has been difficult to glean. This is in part because behaviorally important categories of sound (studied together in this work) have previously been studied in isolation. By bringing these literatures together over these five experiments, this dissertation begins to outline a feature space that encapsulates many different behaviorally relevant sounds with dimensions related to aperiodicity, spectral envelope, spectral variability and fundamental frequency.

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