Author Archives: lkeung

Ross at Cognitive Brown Bag Weds. 3/4 at noon

David Ross (postdoc in Rosie Cowell’s Computational Memory and Perception Lab) will be presenting Norm-Based versus Exemplar-Based Models of Face Recognition in the Cognitive Brown Bag series in Tobin 521B at noon Wednesday, March 4. Everyone is welcome – the abstract is below.

Abstract: Face space models have successfully explained a range of findings in the face recognition literature. Debate has centered on whether the faces in face space are represented with respect to norms or exemplars. Findings from a number of face adaptation studies have been taken as conclusive support for a norm-based model, wherein faces are represented with respect to an abstracted norm/prototype, over an exemplar-based model, wherein faces are represented with respect to other exemplars. Here I will summarize work from my PhD that tested and refuted these claims using computational formalizations of norm and exemplar models. I will also present the results of some new simulations that indicate that it is actually norm-based models that are unable to account for the data.

Cowell at NSB Seminar Series Weds. 2/25 at 4 p.m.

Rosie Cowell (UMass Psychological and Brain Sciences) will be presenting Do amnesics forget because old things look new or because new things look old? in the NSB Seminar Series in 222 Morrill II at 4 p.m. Wednesday, February 25. Everyone is welcome – the abstract is below.

Abstract: I will describe a computational model of object recognition memory in perirhinal cortex (PRC) that provides a novel account of why damage to this MTL structure causes individuals to forget. The theory challenges the widely held assumption that the MTL is primarily a memory region. According to the theory, PRC is not a module for object memory, as assumed in most theories of amnesia, but rather a brain region that stores representations of the conjunctions of visual features possessed by complex objects. These representations allow PRC to engage in hyper-specific perception, enabling it to distinguish between particular objects that have been seen before (e.g., my blue Honda with a dent in the side) versus ones that have never been seen before (e.g., a blue Honda I have never seen before). It is this facility with hyper-specific perception that underlies the role of PRC in object memory. The model accounts for the classic findings concerning impaired recognition memory following perirhinal cortex lesions. In addition, it makes novel predictions, for example that brain damage causes a subject to forget not because familiar objects appear new, but because new objects appear familiar. I present simulation results demonstrating this novel prediction, along with findings from rats and humans that provide support for it.

Cox at Cognitive Brown Bag Weds. 2/25 at noon

Greg Cox of Syracuse University will be presenting A dynamic approach to recognition memory in the Cognitive Brown Bag series in Tobin 521B at noon Wednesday, February 25. He’ll be discussing a computational model of recognition memory that he developed with Richard Shiffrin that accommodates both response time and accuracy data. Everyone is welcome.

Dillon at Cognitive Brown Bag Weds. 2/18 at noon

Brian Dillon (UMass Linguistics) will be presenting Which noun phrases is this verb supposed to agree with… and when? in the Cognitive Brown Bag series in Tobin 521 at noon Wednesday, February 11. Everyone is welcome – the abstract is below.

Abstract: The study of agreement constraints has yielded much insight into the organization of grammatical knowledge, within and across languages. In a parallel fashion, the study of agreement production and comprehension have provided key data in the development of theories of language production and comprehension. In this talk I present work at the intersection of these two research traditions. I present the results of experimental research (joint work with Adrian Staub, Charles Clifton Jr, and Josh Levy) that suggests that the grammar of many American English speakers is variable: in certain syntactic configurations, more than one NP is permitted to control agreement (Kimball & Aissen, 1971). However, our work suggests that this variability is not random, and in particular, optional agreement processes are constrained by the nature of the parser. We propose that variable agreement choices arise in part as a function of how the parser stores syntactic material in working memory during the incremental production of syntactic structures.

Sadil at Cognitive Brown Bag Weds. 2/11 at noon

Patrick Sadil (lab manager of Rosie Cowell’s Computational Memory and Perception Lab) will be presenting Visual Recollection in the Cognitive Brown Bag series in Tobin 521 at noon Wednesday, February 11. Everyone is welcome – the abstract is below.

Abstract: It is widely agreed that two processes – ‘recollection’ and ‘familiarity’ – contribute to performance on episodic recognition. Furthermore, these processes have been related to separate brain structures within MTL (e.g., Brown and Aggleton, 2001). However, we and others have proposed that both processes are carried out by multiple MTL sub-regions (Cowell et al., 2010; Diana et al. 2007) and what determines engagement of a given MTL region by either recollection or familiarity is the representational content of the memory (e.g., item/context/associations or spatial information). The Representational-Hierarchical (RH) view (Cowell et al. 2010) makes a novel prediction: recollection is a pattern completion process that may be computed by any brain region containing representations that could be used in the service of memory. We tested this prediction as applied to different kinds of visual representations (object, scenes, and object in scenes). For instance, if a subject encodes a visual object at study and is cued with part of the object at test, the RH view predicts that a pattern-completion process of recollecting the object (generating the whole from the part) should be carried out in object-representing regions (e.g., perirhinal cortex) without requiring hippocampal involvement. Behaviorally, this would amount to recollection in a non-associative memory task. We examined the behavioral effects of visual pattern completion using the process dissociation procedure (PDP) of Jacoby (1991). Following study, subjects were presented with a part of the studied item (an object part, a scene part, or an object that had been embedded in a scene): a visual analog of the word-stem completion task. They named the studied object or scene either by using (inclusion) or disallowing (exclusion) their memory of the study list. To avoid well-known aggregation biases with this procedure, we used the Bayesian hierarchical model of Rouder et al. (2008) to measure recollection and familiarity. Selective influence of an experimental manipulation was used to validate the use of the PDP; we found that recollection was greater for objects studied twice rather than once, whereas familiarity was unaffected by study frequency. These results provide evidence of visual recollection for objects. Future work will use these stimuli in an fMRI experiment to determine the brain locus of visual recollection for different kinds of visual stimuli.

Park at Developmental Brown Bag, Thurs. 12/4 at 12:45 p.m.

Joonkoo Park of UMass Psychological and Brain Sciences (Developmental) will be presenting in the Developmental Brown Bag series in Tobin 423 at 12:45. Everyone is welcome.

Title: The Neural Basis of Numerical Intuition

Abstract: Humans are endowed with an intuitive sense of number that allows us to roughly perceive and estimate numerosity (i.e., the cardinal value of a set of items) without relying on language. Understanding the cognitive and neural mechanisms that underlie our numerical intuition has recently gained a huge attention for both theoretical and practical reasons. Yet, one central controversy in current research is whether our numerical intuition is indeed based on number or not. This topic is under hot debate because it has been unknown whether the mind and brain is capable of representing number itself or is only capable of encoding number based on other perceptual cues that are necessarily confounded with number, such as the total surface area or density of a dot array. In this talk, I will introduce a novel analytic method, which allows an assessment of the unique contributions of number and other visual properties. I will then describe the application of this approach to a series of passive-viewing event-related-potential studies in human adults that investigate the temporal dynamics of neural sensitivity to number and to other visual properties. The results demonstrate that the human brain is uniquely sensitive to number from very early in the visual stream, providing strong evidence for the existence of a neural mechanism for rapidly and directly extracting numerosity information in the human visual pathway. With the results from five-year-olds performing the same task, I will further discuss how such a neural mechanism may develop from young childhood to adulthood.