title: Discriminating Against New Classes: One-class versus Multi-class Classification

authors: Hempstalk, Kathryn

subjects: computer science

abstract: Many applications require the ability to identify data that is anomalous with respect to a target group of observations, in the sense of belonging to a new, previously unseen ‘attacker’ class. One possible approach to this kind of verification problem is one-class classification, learning a description of the target class concerned based solely on data from this class. However, if known non-target classes are available at training time, it is also possible to use standard multi-class or two-class classification, exploiting the negative data to infer a description of the target class. In this paper we assume that this scenario holds and investigate under what conditions multi-class and two-class Naïve Bayes classifiers are preferable to the corresponding one-class model when the aim is to identify examples from a new ‘attacker’ class. To this end we first identify a way of performing a fair comparison between the techniques concerned and present an adaptation of standard cross-validation. This is one of the main contributions of the paper. Based on the experimental results obtained, we then show under what conditions which group of techniques is likely to be preferable. Our main finding is that multi-class and two-class classification becomes preferable to one-class classification when a sufficiently large number of non-target classes is available.

text: Discriminating Against New Classes: One-class versus Multi-class Classification Many applications require the ability to identify data that is anomalous with respect to a target group of observations, in the sense of belonging to a new, previously unseen ‘attacker’ class. One possible approach to this kind of verification problem is one-class classification, learning a description of the target class concerned based solely on data from this class. However, if known non-target classes are available at training time, it is also possible to use standard multi-class or two-class classification, exploiting the negative data to infer a description of the target class. In this paper we assume that this scenario holds and investigate under what conditions multi-class and two-class Naïve Bayes classifiers are preferable to the corresponding one-class model when the aim is to identify examples from a new ‘attacker’ class. To this end we first identify a way of performing a fair comparison between the techniques concerned and present an adaptation of standard cross-validation. This is one of the main contributions of the paper. Based on the experimental results obtained, we then show under what conditions which group of techniques is likely to be preferable. Our main finding is that multi-class and two-class classification becomes preferable to one-class classification when a sufficiently large number of non-target classes is available.

year: 2008

title: Catania's Concept of the Operant Revisited: Empirical Analysis of Response Variation and Controlling Contingencies

authors: Oliver, Gary Kelson

subjects: Operant

abstract: Six Shaver‐Starcross hens with no prior experimental experience served as participants in two experiments which were designed to empirically test Catania's concept of the operant. The stimulus consisted of a cream coloured rectangle against a black background shown on a standard LCD computer monitor. An infrared touch screen mounted to the front of the LCD monitor recorded the location of all responses made by the participants. Experiment one consisted of autoshaping the rectangle pecking response. This was done using an automated computer program designed to eliminate latencies between responses and reinforcement, as well as positional biases which may have been introduced via manual autoshaping. The program successfully eliminated latencies and positional biases introduced by the experimenter, but took longer than anticipated to autoshape the desired response in the participants. It is suggested that procedural differences account for the unusual length of time taken to autoshape the participants in this experiment. Preliminary inquiry investigating procedural differences shows that it may be possible to model speed of acquisition more accurately than done so at present, without retrospective analysis of the acquisition data itself. In experiment two the active, reinforced zone of the rectangle was reduced. The participants had no visible cue demarcating active and inactive zones of the rectangle, yet in accordance with Catania's operant, responding across all participants came to fall within the active, reinforced zone of the rectangle. The results; shifts in response distributions in relation to the changes in contingencies, offer empirical support for Catania's operant in terms of positive reinforcement across a single parameter of responding. The implications of these findings imply that when variability in responding is important; for example in learning, exploring, creating, and problem solving, Catania's operant may be favourable over Skinner's operant as a vehicle for identifying and controlling variables associated with behavioural outcomes due to its greater topographical inclusivity. Contemporary behavioural analysis favours a behavioural systems approach where the respondent and operant class distinction merges; the environment affects the organism as much as the organism affects the environment. Catania's operant is complementary to behavioural analysis in this vein.

text: Catania's Concept of the Operant Revisited: Empirical Analysis of Response Variation and Controlling Contingencies Six Shaver‐Starcross hens with no prior experimental experience served as participants in two experiments which were designed to empirically test Catania's concept of the operant. The stimulus consisted of a cream coloured rectangle against a black background shown on a standard LCD computer monitor. An infrared touch screen mounted to the front of the LCD monitor recorded the location of all responses made by the participants. Experiment one consisted of autoshaping the rectangle pecking response. This was done using an automated computer program designed to eliminate latencies between responses and reinforcement, as well as positional biases which may have been introduced via manual autoshaping. The program successfully eliminated latencies and positional biases introduced by the experimenter, but took longer than anticipated to autoshape the desired response in the participants. It is suggested that procedural differences account for the unusual length of time taken to autoshape the participants in this experiment. Preliminary inquiry investigating procedural differences shows that it may be possible to model speed of acquisition more accurately than done so at present, without retrospective analysis of the acquisition data itself. In experiment two the active, reinforced zone of the rectangle was reduced. The participants had no visible cue demarcating active and inactive zones of the rectangle, yet in accordance with Catania's operant, responding across all participants came to fall within the active, reinforced zone of the rectangle. The results; shifts in response distributions in relation to the changes in contingencies, offer empirical support for Catania's operant in terms of positive reinforcement across a single parameter of responding. The implications of these findings imply that when variability in responding is important; for example in learning, exploring, creating, and problem solving, Catania's operant may be favourable over Skinner's operant as a vehicle for identifying and controlling variables associated with behavioural outcomes due to its greater topographical inclusivity. Contemporary behavioural analysis favours a behavioural systems approach where the respondent and operant class distinction merges; the environment affects the organism as much as the organism affects the environment. Catania's operant is complementary to behavioural analysis in this vein.

year: 2009

title: Spill-over of sustainability values and practices - a psychology PhD thesis proposal

authors: Rua, Mohi

subjects: Maori

abstract: The following presentation relates to my proposed PhD topic. As an audience you’re probably reading the title and wondering what relevance my topic has to the symposium theme Claiming Spaces. My immediate response is ‘nothing’. Nada, zilch, kore. As a ‘fill-in’ speaker for a presenter unable to be here, I’m reminded that despite my topics irregularity in the programme, I claim a space as both a psychologist and Maori person seeking to work with in the field of sustainability and conservation. Psychologists and Maori are interested in more than mental health and clinical investigation. We are interested in how the world goes around and seek to claim a space here too. So, this symposium and my participation DOES have relevance and I’d like to acknowledge those who remind me so. Let’s take a peep into my world for the next 3 years.

text: Spill-over of sustainability values and practices - a psychology PhD thesis proposal The following presentation relates to my proposed PhD topic. As an audience you’re probably reading the title and wondering what relevance my topic has to the symposium theme Claiming Spaces. My immediate response is ‘nothing’. Nada, zilch, kore. As a ‘fill-in’ speaker for a presenter unable to be here, I’m reminded that despite my topics irregularity in the programme, I claim a space as both a psychologist and Maori person seeking to work with in the field of sustainability and conservation. Psychologists and Maori are interested in more than mental health and clinical investigation. We are interested in how the world goes around and seek to claim a space here too. So, this symposium and my participation DOES have relevance and I’d like to acknowledge those who remind me so. Let’s take a peep into my world for the next 3 years.

year: 2008