Darius Pfitzner

Characterization and evaluation of similarity measures for pairs of clusterings

In evaluating the results of cluster analysis, it is common practice to make use of a number of fixed heuristics rather than to compare a data clustering directly against an empirically derived standard, such as a clustering empirically obtained from human informants. Given the dearth of research into techniques to express the similarity between clusterings, there is broad scope for fundamental research in this area. In defining the comparative problem, we identify two types of worst-case matches between pairs of clusterings, characterised as independently codistributed clustering pairs and conjugate partition pairs. Desirable behaviour for a similarity measure in either of the two worst cases is discussed, giving rise to five test scenarios in which characteristics of one of a pair of clusterings was manipulated in order to compare and contrast the behaviour of different clustering similarity measures. This comparison is carried out for previously-proposed clustering similarity measures, as well as a number of established similarity measures that have not previously been applied to clustering comparison. We introduce a paradigm apparatus for the evaluation of clustering comparison techniques and distinguish between the goodness of clusterings and the similarity of clusterings by clarifying the degree to which different measures confuse the two. Accompanying this is the proposal of a novel clustering similarity measure, the Measure of Concordance (MoC). We show that only MoC, Powers’s measure, Lopez and Rajski’s measure and various forms of Normalised Mutual Information exhibit the desired behaviour under each of the test scenarios.

Vocational and Higher Education in Australia: A Need for Closer Collaboration.

An important way to improve access for groups that are under-represented in tertiary education is to facilitate the movement of students from vocational education and training to higher education institutions. However, there is substantial evidence of rigidities and obstacles to such a closer integration between these two sectors. This paper discusses the problems experienced by students currently articulating from vocational education and training to higher education institutions, identifies impediments to collaborative pathways and suggests measures for overcoming such obstacles.

Language teaching in a mixed reality games environment

How do you develop a game that is provably educational, that is engaging from pre-school to adult, and that independently targets different language ability and world experience/maturity? Our purpose is to teach students of German or English as a Second Language in the same way that a baby learns a First Language. Children acquire language automatically without overt teaching, without conjugating verbs, looking up dictionaries or taking complex classes in syntax and morphology. They acquire through being immersed in an environment in which they have to learn to communicate in the language in order to achieve a variety of social and personal goals. In this project we provide a mixed environment with real toys for the learner to play with, and a simulated environment and a simulated teacher/caregiver to interact with. Whilst young children may be happy building towers and bridges out of wooden blocks, older children and adults cannot be expected to find motivating goals from the same tasks as a baby tackles as s/he simultaneously learns about the world and his/her language, culture and society. This paper explores the methodology we are developing to independently control for degree of language knowledge and degree of world experience.

A lean online approach to human factors research

Arranging sufficient research participation within time and resource constraints is seldom an easy feat. Often, such constraints are a detriment to thorough empirical evaluation of human-computer interfaces. Our objective is to develop the means to test and construct human models which when applied to interface and system development, result in efficient human computer interactions. We report an online platform for experiment delivery to diverse locations with an emphasis on alternative non-monetary rewards for participation. Such a platform meets research goals within constraints as it necessitates a simple web server and web programming. Also addressed are the omnipotent issues of ethics, privacy and data integrity that arise in similar proposals.

User keyword preference: the Nwords and Rwords experiments

Everyday, millions of people use some form of text-based interface to search inefficiently for information. This reflects a lack of penetration of key developments in Human Computer Interaction (HCI) designed to expedite document retrieval. In the context of document search, the value of textual language is self-evident for searching natural language documents. However, there has been little human factors research into general user preferences such as the number of words preferred to describe or search for a document. Such heuristics can help to balance processing overheads of tasks like clustering against user cognitive load in the realisation of, overall, more efficient document retrieval process. We report the results from two internet delivered experiments designed to obtain this heuristic information.

Mimicry and expressiveness of an ECA in human-agent interaction : familiarity breeds content!

Background Two experiments investigated the effect of features of human behaviour on the quality of interaction with an Embodied Conversational Agent (ECA). Methods In Experiment 1, visual prominence cues (head nod, eyebrow raise) of the ECA were manipulated to explore the hypothesis that likeability of an ECA increases as a function of interpersonal mimicry. In the context of an error detection task, the ECA either mimicked or did not mimic a head nod or brow raise that humans produced to give emphasis to a word when correcting the ECA’s vocabulary. In Experiment 2, presence versus absence of facial expressions on comprehension accuracy of two computer-driven ECA monologues was investigated. Results In Experiment 1, evidence for a positive relationship between ECA mimicry and lifelikeness was obtained. However, a mimicking agent did not elicit more human gestures. In Experiment 2, expressiveness was associated with greater comprehension and higher ratings of humour and engagement. Conclusion Influences from mimicry can be explained by visual and motor simulation, and bidirectional links between similarity and liking. Cue redundancy and minimizing cognitive load are potential explanations for expressiveness aiding comprehension. Electronic supplementary material The online version of this article (doi:10.1186/s40469-016-0008-2) contains supplementary material, which is available to authorized users.