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(Psychology 3340. Research Seminar in Cognition, Brain, and Behavior) |
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Thursdays at 12:00-1:30pm William James Hall 765 Interested parties from outside the Harvard community are welcome to attend. Subscribe to weekly e-mail reminders Questions: Steve Franconeri, francon@wjh Links: Past speakers Social Lunch Psychology Department |
George Alvarez
Limits on Attentional Selection
Our subjective experience of the visual world has rich detail and a seamless unity. The richness, however, is superficial as many studies show that we can attend to only a small number of objects at any one time. We now show that the unity of visual awareness is illusory as well. We find that our ability to attend to objects is independently constrained in the left and right visual fields as if two separate attentional systems were engaged in these regions. Specifically, in two tracking experiments, twice as many targets can be successfully tracked when they are divided between the left and right hemifields as when they are all presented within the same hemifield. This finding places broad constraints on the anatomy and mechanisms of attentional selection, ruling out a single attentional focus, even one that moves quickly from target to target, and suggests important criteria for human interface design. I will discuss the implications of hemifield independence as well as other limits on our ability to attend to visual objects.
Jeremy Wilmer
Studying visual function using individual differences: a theoretical framework and a study of motion processing
A novel approach to studying visual function, involving the psychophysical evaluation of individual differences, is proposed. By assessing covariation between individuals' performance on tasks assessing multiple visual functions, one may estimate the degree to which these functions are subserved by common underlying mechanisms. This approach is conceptually identical to approaches that associate multiple functions with similar brain regions or brain responses. As with those established methods, functions of interest are isolated with the help of carefully chosen control conditions, then mapped onto an independent source of data: in this case inter-individual variation in performance, in the established cases brain structure or brain function. This approach presents a converging method for addressing questions of functional association, one that adds to our theoretical leverage by relying upon different assumptions than those of physiology-based methods. A study of individual differences in motion processing is presented as a methodological and conceptual illustration of the utility of this approach.
Rachel Keen
Cognitive influences on spatial hearing
In reverberant rooms a listener perceives a sound coming from its source but simultaneously suppresses reflected sound or echoes. This phenomenon is known as the precedence effect because the preceding (original) sound is given heariver weight than its subsequent reflections. Our research has explored this perceptual process and found that listeners are sensitive to the acoustic information contained in the reflected sound even though it is "suppressed". Specifically, information relevant to room acoustics is processed by the listener and influences perception. Examples of relevant acoustic information are delay between lead and lag sounds, filtering of the echo's spectrum by the reflecting surface, and presence vs. absence of an echo at a particular location. Listeners' expectations about ongoing input can raise or lower echo threshold. These findings suggest that the precedence effect is strongly affected by cognition, which constrasts with most current models of the phenomenon.
Tania Lombrozo
Functional explanations and the function of explanation
Explanation is a basic part of everyday life. We wonder why people behave the way they do, why objects have particular features, and why things do or don't happen. But often some kinds of explanations seem more satisfying and appropriate than others. In this talk I'll focus on functional/teleological explanations: explanations in terms of a function or goal. Why do we accept and prefer such explanations in some contexts but not others? For example, we might explain a firetruck's color by appeal to its function (attracting attention), but it would be strange to appeal to a function in explaining the color of the sky. I'll present several experiments that suggest people accept teleological explanation when two conditions obtain: the function invoked in the explanation played a causal role in bringing about what's being explained, and the process by which it did so belongs to some kind of regularity. Other factors, like the domain of the object being explained and the role of human intentions, don't seem to influence people's judgments. I'll conclude with some thoughts about why people might have the teleological intuitions they do.
Ann Senghas
How children turn gesture into grammar: Spatial and temporal segmentation in Nicaraguan Sign Language
The recent emergence of a new sign language among deaf children and adolescents in Nicaragua provides an opportunity to study how linguistic features of a language arise and spread. New features that arise must be successfully transmitted from one generation to the next to survive as part of the language. During this transmission, language form is shaped by both the characteristics of ontogenetic development within individual users and by historical changes in patterns of interaction between users. To capture this process, changes over the past 25 years will be examined within two domains: expressions of manner and path of movement, and expressions of spatial co-reference. These data reveal that, as the new language is learned, holistic and analog expressions are being replaced by discrete, combinatorial expressions. It appears that these new form-function mappings arise among child learners who functionally differentiate previously equivalent forms. The new mappings are then acquired by their age peers (while children), and by subsequent generations of children who learn the language, but not by adult contemporaries. As a result, language emergence is characterized by a convergence on form within each age cohort, and a systematic mismatch in form from one age cohort to the cohort that follows. In this way, each age cohort, in sequence, systematically transforms the language environment for the next, enabling each new cohort of learners to develop further than its predecessors
Jeff Stevens
Selfish minds: psychological constraints on the evolution of cooperation
Models of social interactions predict that reciprocity (repaying an opponent's previous generosity) can stabilize cooperation in social dilemmas. Despite intense theoretical interest in the topic, reciprocity has not been reliably demonstrated in non-human animals, although it is ubiquitous in human society. This mismatch between theory and reality may occur because models of cooperation are incomplete, relying only on evolutionary explanations and ignoring proximate constraints on cooperation. Reciprocity, in particular, may tax animals' quantification, learning, memory, and inhibitory abilities. The time delay associated with reciprocation makes delayed gratification its most significant challenge because animals devalue the future reciprocated rewards. Experimental data on both human and non-human animals confirms the effect of delayed gratification on cooperation. Including proximate constraints will not only provide more realistic models of cooperation, but also generate testable predictions regarding which species are more likely to exhibit complex cooperative behavior such as reciprocity.
Benton Pierce
The Generation and Reduction of False Memories: A Comparison of Younger Adults, Older Adults, and Alzheimer's Disease Patients
False or illusory memories are usually characterized as memories for events that never happened. However, they may also include situations in which one correctly remembers an item, event, or face, but misattributes it to an incorrect source or context. In my talk, I will discuss two separate factors that give rise to false memories: those involving general similarity information or gist, and those involving source confusion. I will compare how these two types of false memories are manifested in younger adults, older adults, and Alzheimer's disease (AD) patients. Furthermore, I will show how these groups differ in their ability to use a recall-to-reject process to reduce false memories under certain conditions.