Thora Tenbrink

Spatial Cognition: Reasoning, Action, Interaction

The Transregional Collaborative Research Center SFB/TR 8 Spatial Cognition pursues interdisciplinary research on a broad range of topics related to the representation and processing mechanisms for intelligent spatial behavior in technical and in natural systems. This contribution gives an overview of the field of research worked on in the SFB/TR 8 Spatial Cognition and presents three representative examples that illustrate the activities in the three research areas Reasoning, Action, and Interaction.

A linguistic ontology of space for natural language processing

We present a detailed semantics for linguistic spatial expressions supportive of computational processing that draws substantially on the principles and tools of ontological engineering and formal ontology. We cover language concerned with space, actions in space and spatial relationships and develop an ontological organization that relates such expressions to general classes of fixed semantic import. The result is given as an extension of a linguistic ontology, the Generalized Upper Model, an organization which has been used for over a decade in natural language processing applications. We describe the general nature and features of this ontology and show how we have extended it for working particularly with space. Treaitng the semantics of natural language expressions concerning space in this way offers a substantial simplification of the general problem of relating natural spatial language to its contextualized interpretation. Example specifications based on natural language examples are presented, as well as an evaluation of the ontologys coverage, consistency, predictive power, and applicability.

Would You Follow Your Own Route Description? Cognitive Strategies in Urban Route Planning.

This paper disentangles cognitive and communicative factors influencing planning strategies in the everyday task of choosing a route to a familiar location. Describing the way for a stranger in town calls for fundamentally different cognitive processes and strategies than actually walking to a destination. In a series of experiments, this paper addresses route choices, planning processes, and description strategies in a familiar urban environment when asked to walk to a goal location, to describe a route for oneself, or to describe a route for an addressee. Results show systematic differences in the chosen routes with respect to efficiency, number of turns and streets, and street size. The analysis of verbal data provides consistent further insights concerning the nature of the underlying cognitive processes. Actual route navigation is predominantly direction-based and characterized by incremental perception-based optimization processes. In contrast, in-advance route descriptions draw on memory resources to a higher degree and accordingly rely more on salient graph-based structures, and they are affected by concerns of communicability. The results are consistent with the assumption that strategy choice follows a principle of cognitive economy that is highly adaptive to the degree of perceptual information available for the task.

Variable Granularity in Route Directions

Abstract This paper addresses changes of spatial granularity in route directions in relation to information needs in multimodal traveling. We outline a model of variability in granularity and apply this model to empirical data. Results reveal that linguistic route directions produced by humans as well as automatically generated web-based services provide the most crucial route elements in hierarchically structured ways that reflect the salient structure imposed by multimodal traveling. However, although the web-based information is impressively comprehensive, human route directions exhibit more flexibility regarding switches of place-related granularity, and they provide more detailed information at complex locations or decision points.

COGNITIVE MODELING OF SPATIAL REFERENCE FOR HUMAN-ROBOT INTERACTION

The question addressed in this paper is which types of spatial reference human users employ in the interaction with a robot and how a cognitively adequate model of these strategies can be implemented. In experiments we explored how human users approach an artificial communication partner, which was designed to mimic spatial reference among humans. Our findings show that spatial reference in human-robot interaction differs from natural situations in human-human interaction in seveal respects. For instance, many users unexpectedly employed fine-grained, path-based, instructions rather than specifying the intended goal object of the action directly. If instructions were not successful, participants created less and less complex descriptions. Those users who did specify the goal object were found to employ those kinds of spatial reference strategies implemented in our computational model. In particular, they exploited the presence of several similar objects by perceiving and referring to them linguistically as a group.

The verbalization of multiple strategies in a variant of the traveling salesperson problem

What kinds of strategies do humans employ when confronted with a complex spatial task, and how do they verbalize these strategies? Previous research concerned with the well-known traveling salesperson problem (TSP) typically aimed at the identification of a generally applicable heuristics that adequately represents human behavior in relation to the abstract task of combining points. This paper adopts a novel perspective in two respects. On the one hand, it addresses the strategies people employ when confronted with a more complex task, involving distractors and feature information rather than identical points. On the other hand, retrospective linguistic representations of the strategies used are analyzed in relation to the behavioral data, using discourse analytic methods. Results show that both the behavioral results and the verbalizations point to a range of strategies related to those proposed for solving abstract TSPs. However, in contrast to earlier accounts in the literature, the participants employ a repertory of multi-faceted strategies and planning processes, simplifying and structuring the problem space across subtasks and processes in flexible ways. These findings provide further insight into the nature of human strategies in spatial problem solving tasks and their retrospective verbalization, highlighting how procedures generally known in the literature may be adapted to more complex tasks, and how they may be verbalized spontaneously.

Route instructions in map-based human-human and human-computer dialogue: A comparative analysis

When conveying information about spatial situations and goals, speakers adapt flexibly to their addressee in order to reach the communicative goal efficiently and effortlessly. Our aim is to equip a dialogue system with the abilities required for such a natural, adaptive dialogue. In this paper we investigate the strategies people use to convey route information in relation to a map by presenting two parallel studies involving human-human and human-computer interaction. We compare the instructions given to a human interaction partner with those given to a dialogue system which reacts by basic verbal responses and dynamic visualization of the route in the map. The language produced by human route givers is analyzed with respect to a range of communicative as well as cognitively crucial features, particularly perspective choice and references to locations across levels of granularity. Results reveal that speakers produce systematically different instructions with respect to these features, depending on the nature of the interaction partner, human or dialogue system. Our further analysis of clarification and reference resolution strategies produced by human route followers provides insights into dialogue strategies that future systems should be equipped with.

Conceptual layers and strategies in tour planning

We present an exploratory study of an everyday navigation planning situation, addressing spatial planning strategies as well as cognitive shifts between the visually available map and the conceptualized real-world environment. Participants were asked to plan a diversified holiday route on an island, with the help of a map representing spatial as well as activity information. Following the task proper, they reported in written form about the problem-solving process. Route trajectories were analyzed with respect to their properties, and reports were analyzed with respect to the represented concepts and linguistic patterns. Results reveal that route trajectories tended to be circular rather than random, with relatively few detours or crossing lines. The underlying spatial planning strategies as represented in the written reports resembled earlier findings on the Traveling Salesperson Problem, providing insights into the extent to which this abstract task transfers to a naturalistic scenario. Most crucially, our linguistic analysis provides new results about the representation of conceptual layers when considering the real-world navigation domain of traveling in relation to the actual table-top map planning domain.

The effect of activity on relevance and granularity for navigation

This paper addresses the role of activity on the construction of route directions. Primary to our conceptualization is that the activity at hand constrains the relevance of spatial information for task performance, as well as the level of granularity at which information is needed. In this paper, we highlight the role of activity for relevance and granularity first based on a review of each of the components involved, and furthermore by a semantic analysis of content patterns in human-generated instructions. The analysis identifies the verbalization styles that are associated with distinct types of activities on the basis of individual keywords that may serve as indicators. We offer a strong theoretical argument for the importance of activities and provide a first step towards an operationalization of this concept, as well as implications for the development of cognitively motivated navigation systems.

The Role of Conceptual and Linguistic Ontologies in Interpreting Spatial Discourse

This article argues that a clear division between two sources of information–one oriented to world knowledge, the other to linguistic semantics–offers a framework within which mechanisms for modelling the highly flexible relation between language and interpretation necessary for natural discourse can be specified and empirically validated. Moreover, importing techniques and results from formal ontology provides the formal underpinnings necessary for representing these sources of information appropriately. The result is a computationally specifiable model of dialogic interaction within which flexible discourse interpretation occurs as the result of inter-ontology mappings between our two sources of information. These mappings are dynamically negotiated according to the concrete discourse moves of interlocutors. The article draws on ongoing empirical studies in spatial discourse, where interlocutors jointly solve varieties of spatially embedded tasks, and suggests that ontological formalization benefits the construction of computational dialogue systems.