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Q733 Colloquium

Colloquia occur: Selected Mondays at 4:00 pm - 5:00 pm - Room PY 101.
Colloquia titles will be posted as they become available.

Organizer: Rob Goldstone
Phone: 855-4853

Spring 2015 Q733 Colloquia


Mar 2, 2015: Tony Movshon
Psychology Rm. 101, 4-5pm
Title: Cortical and perceptual processing of visual form
Abstract: The perception of complex visual patterns emerges from neuronal activity in a cascade of areas in the primate cerebral cortex. Neurons in the primary visual cortex (V1) represent information about the local orientation and scale of image elements, but the role of the second visual area (V2) is enigmatic. We made synthetic images that contain complex features found in naturally occurring visual textures, and used them to stimulate macaque V1 and V2 neurons. Most V2 cells respond more vigorously to these stimuli than to matched control stimuli lacking naturalistic structure, while V1 cells do not. fMRI measurements in humans reveal differences in V1 and V2 responses to the same textures that are consistent with neuronal measurements in macaque. The ability of human observers to detect naturalistic structure is well predicted by the strength of the neuronal and fMRI responses in V2 but not in V1. Downstream of V2, human fMRI measurements show that the representation of true natural scenes becomes a more prominent driving feature of cortex. These results reveal something of the way that information about elementary visual features is transformed into the specific representations of scenes and objects found in areas higher in the visual pathway.

Mar 9, 2015: Richard Ivry
Psychology Rm. 101, 4-5pm
Title: Embodied Decision Making: System interactions in sensorimotor adaptation and reinforcement learning
Abstract: Two well-established literatures have provided elegant models of sensorimotor adaptation and decision making, with relative little connection between the two. I will discuss ways in which we can bring these two worlds together. In the first part of the talk, I will discuss work that has brought into focus the relevance of multiple learning mechanisms for sensorimotor learning. In particular, I will examine how strategic processes interact with a cerebellar error-based learning system in sensorimotor adaptation, highlighting a distinction between error signals that improve action execution or action selection. In the second part, I will turn to learning in decision making tasks, asking how competence in motor execution might be incorporated in models of reinforcement learning. Our work here addresses the question of how an agent determines if the absence of reward reflects a property of the stimulus or an error in motor execution. We suggest that sensorimotor errors provide a “gating” signal to regulate reinforcement learning, providing a simple solution to this fundamental credit assignment problem.

Mar 23, 2015: Fred Dyer
Psychology Rm. 101, 4-5pm
Title: Evolution of search in nectar-feeding bees
Abstract: William James observed that searching for ideas in one's mind resembles a search for objects in physical space. Research with humans and animals suggest that this resemblance arises because cognitive and physical search share common neural mechanisms and a common evolutionary heritage. Among the evidence for this claim are similarities between cognitive search in humans and behavioral search in animals, including invertebrates. However, most animal examples involve simple modulation of search in the vicinity of food, which little resembles the flexible, hierarchical organization of cognitive search. I study bees as they search for food among multiple locations for up to an hour. The behavior reveals that bees maintain multiple search options in memory, adaptively shift which options they pursue over time, and shift between local and global search, implying a hierarchical organization of the underlying memory. Because the work compared honey bees and bumble bees, the results also shed light on the evolutionary pressures that may have shaped search behavior in response to changing incentives. Whether or not this represents a homolog of cognitive search, this research sets the stage for further investigations of the neural and evolutionary basis of search behavior in animals.

Apr 20, 2015: Rafael Nunez
Psychology Rm. 101, 4-5pm
Title: How much mathematics is ‘hard-wired’? (none): Lessons from the cognitive science of the number line
Abstract: Mathematics is a unique body of knowledge. The very entities that constitute what mathematics is are idealized mental abstractions that cannot be perceived directly through the senses (e.g., the Euclidean point, whose only property is to have location, but no extension). So, what kind of thing is mathematics? In academia, this question is usually studied in formal logic, philosophy, and the history of mathematics. And, the whole enterprise has either a platonic flavor, in which mathematical entities are seen as timeless eternal facts existing outside of human beings, or a formalist one, where mathematics is reduced to the manipulation of meaningless symbols. In this talk I’ll address this question with a naturalistic approach that takes into account the biological and socio-cultural constrains under which the human mind unfolds. I will concentrate on the critical properties of number-to-space mappings—fundamental to modern mathematics, and more specifically, on the concept of the number line, which is arguable one the simplest but richest examples of the power of such mappings. What are the cognitive origins of the number line? Are the intuitions underlying the number line "hard-wired"? Is the number line a cultural construct? Contemporary research in the (human and non-human) psychology and neuroscience of number cognition has largely assumed that the representation of number is inherently spatial and that the number-to-space mapping is, in humans, a universal intuition rooted directly in brain evolution. I'll review material from the history of mathematics as well as empirical results from two of our recent studies to defend a radically different picture: the representation of number is not inherently spatial and the intuition of mapping numbers to space is not universal. In one study we show that there are non-spatial representations of numbers that co-exist with spatial ones, as indexed by instrumental manual actions, such as squeezing and bell-hitting, and non-instrumental actions, such as vocalizing. Moreover, the results suggest that the number-to-line mapping—a *spatial* mapping— is not a product of the human biological endowment but that it has been culturally privileged and enhanced. The other study, which we carried out with the Yupno of the remote mountains of Papua New Guinea, shows experimentally that individuals from a culture that has a precise counting system (and lexicon) for numbers greater than twenty— but, importantly, no measurement practices— lack the intuition of a number-to-line mapping, suggesting that this intuition is not universally spontaneous, and therefore, unlikely to be rooted directly in brain evolution. The number-to-line mapping appears to be learned through— and continually reinforced by— specific cultural practices, such as measurement tools, writing systems, and elementary mathematics education. It is over the course of exposure to these cultural practices that well-known brain areas such as the parietal lobes are recruited to support number representation and processing.

Previous Q733 Colloquia