I am interested in how bilingual individuals manage and control their two languages and in whether there are broader cognitive and neural consequences of exercising this control throughout daily life. To date, there is copious evidence that bilinguals coactivate information about both of their languages even when they intend to use a single language. In my work, I investigate whether bilinguals can exploit contextual cues (such as the requirement to use one language and not the other) and linguistic cues (such as cross-linguistic differences) to select the intended language during comprehension and production. I also investigate the neurocognitive mechanisms that underlie language control.

Below you can find more information about these threads of work. They were conducted together in collaboration with mentors and colleagues at Penn State University; University of California, Riverside; or McGill University. My research projects have, at various times, been supported by the National Science Foundation (USA), the National Institutes of Health (USA), and the Social Sciences and Humanities Research Council (Canada).



Contextual and linguistic mechanisms of language control

Overall, I show that it is surprisingly difficult for bilinguals to reduce activation of the unintended language. The requirement to read only in Spanish or only in English does not change the extent to which both languages are activated for highly proficient Spanish-English bilinguals. We (Gullifer, Kroll, & Dussias, 2013) report similar magnitudes of co-activation for these single language conditions as for conditions in which both languages are required. Frontiers, estimates that our report is in the top 10% of its articles in terms of impact, and this work has been featured in some press releases (e.g., by the NSF) and by various media outlets (e.g., Penn State News, Science Daily, and Psych Central).

In my dissertation (funded by an NSF Dissertation Research Improvement Grant), I assess whether bilinguals who are fluent speakers of Spanish and English can use syntactic structures that are specific to Spanish to reduce or eliminate co-activation from English. At present, this work is being written up for publication.

Cognitive and neural mechanisms of language control

I am also interested in the cognitive mechanisms that underlie bilingual language processing. Many studies show that bilinguals recruit inhibitory or attentional mechanisms to suppress co-activation from the unintended language and direct attention toward the target language. A growing body of literature suggests that a life-time of experience using these executive control mechanisms can result in changes to the brain networks that support language and executive control, and may help shield against the symptoms of age-related cognitive decline and dementia in comparison to monolingual speakers. My recent work investigates the universality of these mechanisms and the extent to which individual differences in language experience underlie these neurocognitive changes.

One question of interest is the universality of bilingual recruitment of executive control mechanisms. Most bilinguals tested in psycholinguistic experiments are highly educated, literate adults who are attending or who have attended research universities, but this profile is not representative of all language users. We (Dussias, Gullifer, & Poepsel, 2016) show that bilingual speakers of Spanish and Palenquero, a creole language spoken in Columbia that traditionally has no standardized writing system (though this is changing), recruit similar inhibitory mechanisms as reported in typical psycholinguistic experiments on bilingualism. This finding also has consequences for linguistic debates about whether Palenquero is merging with Spanish, one of Palenquero's source languages. Specifically, they suggest that the two languages are distinctly represented in the minds of the bilinguals in our sample. To our knowledge, this may be the first reported study on language control in a population of creole-speaking bilinguals.

Another question of interest is what the neural mechanisms are that the underlie language control. There is now a general consensus that there are several interrelated networks, or circuits, in the brain that accomplish various cognitive tasks, such as memory, language, and various forms of executive control. There is also a general consensus that the networks for language and executive control are tightly integrated for bilingual speakers. In a paper forthcoming in Neuropsychologia, we (Gullifer et al., 2018; preprint available here) show that individual differences in bilingual experience (both in terms of language acquisition history and current daily usage) are associated with intrinsic brain organization. We replicate a finding that bilinguals who acquire their two languages early in life have highly connected frontal brain regions which are thought to be involved in language and inhibitory control. Crucially, we also show a novel result: that the diversity of language use (i.e., the extent to which two languages are used together in various social settings) is also associated with intrinsic brain organization. Specifically, bilinguals who use their two languages in a highly diverse fashion (i.e., to a similar extent throughout their social spheres) show greater connectivity in a subcortical brain network associated with attention, contextual integration, and language articulation. These results suggest that both acquisition and daily use matter for brain organization of networks involved in language and executive control.

Research training

Undergraduate research


I received my BA in Linguistics and Psychology from The University of Massachusetts Amherst in 2007. At UMass, I worked in the The Clifton-Frazier Lab under the direction of Charles Clifton and Lyn Frazier.

Post-baccalaureate research


Following my undergraduate studies, I joined The Pennsylvania State University community as a Research Technologist in the Center for Language Science. The CLS is an interdisciplinary group of linguists, psycholinguists, applied linguists, speech-language pathologists, speech scientists, and cognitive neuroscientists who share a common interest in language acquisition and bilingualism. From 2007 - 2009, I was the resident webmaster for the CLS and conducted various administrative duties.

In addition to working in the Center for Language Science, I also spent a large portion of my time working in the ISÍ (I see) Eye-tracking Laboratory with Paola Dussias and in the Bilingualism, Mind, and Brain Lab with Judith Kroll.

Masters and Doctoral research


In 2009 I became a graduate student in the Psychology Department at Penn State where I continued working with Judith Kroll and Paola Dussias. I received my MS in Psychology in 2011. I then received my dual-title PhD in Psychology and Language Science from The Pennsylvania State University in 2015.

Post-doctoral research


In 2015, I moved to Montréal to join McGill University as an NIH-funded postdoctoral fellow in the McGill Language & Multilingualism Laboratory, under the direction of Debra Titone, and in the Language Experience and the Brain Laboratory, under the direction of Denise Klein.