Cognitive Science Colloquium
All meetings take place on Thursdays, 3.30-5.30 pm in Bioscience Research Building 1103, unless otherwise indicated.
September 7 — Michael Frank (Psychology, Stanford).
Title: Bigger data about smaller people: Studying children’s language learning at scale
Abstract: How do children acquire a language? Decades of work have provided a roadmap of principles and mechanisms for early language learning as attested by small-scale laboratory tasks. But there is not yet a convincing empirical synthesis of this work that addresses both the systematicity and ubiquity of language learning and the variability of learning trajectories across children. In this talk I will describe some initial steps towards such a synthesis. This research integrates high-density data from individual children learning a single language and summary data from tens of thousands of children learning more than a dozen languages. Taken together, the data support a hybrid picture in which children slowly accumulate knowledge in rich social contexts but also show evidence for surprisingly fast grammatical abstractions.
September 14 — Ed Awh (Institute for Mind and Biology, Chicago).
Title: Tracking the spatial and temporal dynamics of online spatial representations with rhythmic brain activity
Abstract: A substantial body of evidence suggests that neural activity in the alpha frequency band (8-12 Hz) covaries with the locus of covert spatial attention, such that attention to one visual field yields a sustained decline in alpha power at contralateral electrode sites. In our work, we have exploited this covariation by using an inverted encoding model to reconstruct spatial response profiles (termed channel tuning functions, or CTFs) based on the topography of alpha activity on the human scalp. Thus, in a task that required the storage of locations in working memory, we observed a graded profile of activity across spatial channels that peaked at the stored location during both the encoding and delay periods of the task. These spatial CTFs provide an opportunity to quantify the basic tuning properties of online spatial memories to examine how the precision of neural representations changes with manipulations of the probability of storage or the number of items stored. In addition, I’ll show that the same method can be used to track the locus and timing of covert attention, as well as the retrieval of spatial representations from long term memory. These findings demonstrate the integral role that alpha band activity plays in the online representation of space, and provide a powerful new approach for tracking these representations during during ongoing cognition and without requiring overt behavioral responses.
October 5 — Roger Levy (Brain & Cog Sci, MIT). – Note: in BPS (Bio-Psych) 1208
Title: Life at the edge of the lexicon: Productive knowledge and direct experience in language processing and acquisition.
Abstract: The infinite generative potential of human language derives from our ability to analyze complex linguistic input into simpler units, store those units in memory, and productively recombine those units into new expressions. This is the cycle of comprehension, acquisition, and production through which human languages persist and change through the history of a speech community. But what are these units of comprehension, acquisition, and production? The tension between combinatorial and holistic representation of complex linguistic expressions plays a central role in debates on language processing and acquisition. Here I describe work combining probabilistic models and new large datasets to investigate this tension and uncover the respective contributions of productive knowledge and direct experience. In processing, we focus on binomial expressions (salt and pepper - pepper and salt), finding a frequency-driven tradeoff between the two knowledge sources and a frequency-dependent level of idiosyncrasy in binomial ordering preference across binomials in the language. The former is explained by a rational model of learning from limited experience; the latter we account for with an evolutionary model of transmission of ordering preferences over time. In acquisition, we focus on determiner-noun combinations (“the ball”, “a cold”) and develop a novel Bayesian model to infer the strength of contribution of productive knowledge evident in child speech. We find evidence of low initial levels of productivity and higher levels later in development, consistent with the hypothesis that the earliest months of multi-word speech are not generated using rich grammatical knowledge, but that grammatical productivity emerges rapidly thereafter.
October 19 — Ingrid Olson (Psychology, Temple).
Title: A Dynamic Neural Architecture for Social Memory
Abstract: Social behavior is often shaped by the rich storehouse of biographical information that we hold for other people. During our daily social interactions we rapidly and flexibly retrieve a host of biographical details about individuals in our social network, which often guide our decisions as we navigate complex social interactions. Even abstract traits associated with an individual, such as their political affiliation, can cue a rich cascade of person-specific knowledge. I will discuss research from my laboratory showing that a distributed neural circuit, with a hub in the anterior temporal lobe, allows us to rapidly retrieve person knowledge by coordinating interactions with a distributed network to support the flexible retrieval of person attributes.
October 26 — Molly Crockett (Psychology, Yale).
Title: Moral Flexibility: Insights from Neuroscience
Abstract: Classical models of antisocial behavior propose that violence arises out of a failure of lateral prefrontal cortex (LPFC) to “put the brakes” on aggressive impulses originating in subcortical regions such as the amygdala and striatum. A new, alternative model proposes that LPFC does not directly inhibit aggressive impulses, but instead flexibly modulates the value of aggressive acts via corticostriatal circuits. I will present the first empirical evidence directly supporting the alternative model. In a series of behavioral, pharmacological and neuroimaging experiments we observed healthy adults as they decided whether to anonymously inflict pain on themselves or strangers in exchange for money. We find that most people would rather harm themselves than others for profit. This moral preference correlated with neural responses to profit, where participants with stronger moral preferences had lower dorsal striatal responses to profit gained from harming others. LPFC encoded profits gained from harming others, but not self, and tracked the blameworthiness of harmful choices. Moral decisions modulated functional connectivity between LPFC and the profit-sensitive region of dorsal striatum. Increasing central dopamine levels with the dopamine precursor levodopa eliminated moral preferences. The findings suggest moral behavior is linked to a neural devaluation of reward realized by a prefrontal modulation of striatal value representations. This mechanism implies that the moral value of actions is flexibly guided by neural representations of social norms. If norms change, so then do the values that guide actions. Supporting this view, re-framing decisions to harm others as being in service of a noble cause eliminated moral preferences. The flexibility of value representations in the brain may hold the key to understanding why people with good intentions can sometimes do terrible things.
November 30 — Virginie van Wassenhove (INSERM, Paris).
December 7 — Helen Tager-Flusberg (Psychology, Boston University).