INTERACTIONS WITH LANGUAGE IN HUMAN OLFACTORY PERCEPTION

People are notoriously bad at identifying odors by name. Why might this be? Theories range from competition for cognitive resources to poor neural connectivity to inferiority at the level of sensory transduction and perception. Here we suggest that human olfaction on its own is a measurably precise, rich, and nuanced sense. And further, we suggest that the addition of labels automatically and irresistibly changes people’s experience of odors. In the context of this thesis, we use language as a tool for understanding olfaction specifically. But also, the study of olfaction can be used as a tool for understanding perception more generally. Difficulty naming odors can be an exploitable feature rather than a bug in the system. It means that certain aspects of perception and cognition that are entangled for other sensory systems are separable in olfaction. In this thesis, we address the important gap in olfactory understanding, specifically the way odors interact with language. In Chapter 1, we found that behavioral similarity ratings for a set of everyday odors showed high agreement across participants. Adding labels to odors caused systematic shifts in response patterns that induced people to incorporate more conceptual and physical features of source objects into their evaluation of odors. In Chapter 2, we extended our previous findings by asking whether shifts in similarity responses reflected perceptual or conceptual changes. We found a dissociation between mental representations of odors and olfactory perception. Despite reliable changes in odor experience previously reported by participants, we found no change in performance in an odor mixture discrimination task when labels were added to odor stimuli. In Chapter 3, we evaluated the types of guesses people made when trying to identify odors without any visual or context clues. Follow-up analyses demonstrated that odor naming ability is widely distributed, even within a relatively homogeneous test population (and even after controlling for low-level olfactory perceptual ability and general verbal ability) and that some odor stimuli are reliably easier to name than others. Taken together, these results suggest there is a greater depth and complexity to human olfactory experience than previously thought. Similarity ratings of odors are not only malleable with verbal context, they are separable from olfactory perception and they reflect previously unknown dimensions of odor experience

Predicting Actions Before They Occur

Humans are experts at reading others’ actions in social contexts. They efficiently process others’ movements in real-time to predict intended goals. Here we designed a two-person reaching task to investigate real-time body reading in a naturalistic setting. Two Subjects faced each other separated by a plexiglass screen. One (Attacker) was instructed to tap one of two targets on the screen and the other (Blocker) was told to tap the same target as quickly as possible. Reaction times were fast, much faster than reaction times to a dot projected on the screen moving in the same manner. This suggests Blockers use subtle preparatory movements of Attackers to predict their goal. Next, using video recordings of an Attacker, we showed that removing the preparatory cues slows reaction times and changing them could trick the Blockers to choose the wrong target. We then occluded various body parts of the Attacker and showed that reaction times slow down only when most of the body of the Attacker is occluded. This suggests that preparatory cues are distributed over the body of the Attacker. We saw no evidence of learning during the experiment as reaction times remained constant over the duration of the session. Taken together, these results suggest that in social contexts humans are able to use their knowledge of the biomechanical constraints on the human body to efficiently process preparatory cues from the body of their interaction partner in order to predict their intentions well before movement begins.This work was supported by the Center for Brains, Minds and Machines (CBMM), funded by NSF STC award CCF - 1231216

Object-Based Benefits without Object-Based Representations

The organization of visual information into objects strongly influences visual memory: Displays with objects defined by two features (e.g. color, orientation) are easier to remember than displays with twice as many objects defined by one feature (Olson & Jiang, 2002). Existing theories suggest that this ‘object-benefit’ is based on object-based limitations in working memory: because a limited number of objects can be stored, packaging features together so that fewer objects have to be remembered improves memory performance. This view predicts that memory for "packaged features" should be correlated (if you remember one feature of an object you should remember the object’s other features). Counter to this prediction, we show that some object features are stored largely independently. Participants were instructed to remember the colors and orientations of 5 colorful isosceles triangles (five-object condition) or the color of 5 colorful circles and the orientation of 5 black isosceles triangles (ten-object condition). After encoding (1200ms) and retention (900ms), memory was assessed with a continuous report for both features. Critically, participants reported both features of the same item in the five-object condition, allowing us to determine whether features were stored in an integrated fashion. Here we replicate the object-benefit: participants remembered twice as many features when arranged in 5 versus 10 objects. However, in the five-object condition memory for the color and orientation of an object was largely independent—when participants failed to accurately report the color or orientation of an object they were often quite accurate at judging the object's other feature. These results challenge the claim that the object-benefit is driven by the storage of integrated object representations, and require a revision of the concept of object-based memory representations. We propose that working memory is object-based in regard to the factors that enhance performance, but is feature-based at the level of representational failure.Psycholog

Odor discrimination is immune to the effects of verbal labels

Abstract For many odors that we encounter in daily life, we perceive their qualities without being able to specifically identify their sources—an experience termed the “tip-of-the-nose” phenomenon. Does learning an odor’s identity alter our experience of it? Past work has shown that labeling odors can alter how we describe and react to them, but it remains an open question whether such changes extend to the level of perception, making an odor actually smell different. Here, in a set of odor classification experiments we tested whether attaching labels to odors can alter their perceptual discriminability. We found that even for odors whose reported similarity changed markedly when their identities were revealed, their discriminability remained unchanged by labels. Our findings indicate that two critical functions of olfaction—parsing the odor environment and supporting the subjective experience of odor qualities—access distinct odor representations within the olfactory processing stream

A dedicated mental resource for intuitive physics

Summary: Countless decisions and actions in daily life draw on a mental model of the physical structure and dynamics of the world – from stepping carefully around a patch of slippery pavement to stacking delicate produce in a shopping basket. People can make fast and accurate inferences about how physical interactions will unfold, but it remains unclear whether we do so by applying a general set of physical principles across scenarios, or instead by reasoning about the physics of individual scenarios in an ad-hoc fashion. Here, we hypothesized that humans possess a dedicated and flexible mental resource for physical inference, and we tested for such a resource using a battery of fine-tuned tasks to capture individual differences in performance. Despite varying scene contents across tasks, we found that performance was highly correlated among them and well-explained by a unitary intuitive physics resource, distinct from other facets of cognition such as spatial reasoning and working memory