title: A survey on feature drift adaptation: Definition, benchmark, challenges and future directions

authors: Barddal, Jean Paul

subjects: Science & Technology

abstract: Data stream mining is a fast growing research topic due to the ubiquity of data in several real-world problems. Given their ephemeral nature, data stream sources are expected to undergo changes in data distribution, a phenomenon called concept drift. This paper focuses on one specific type of drift that has not yet been thoroughly studied, namely feature drift. Feature drift occurs whenever a subset of features becomes, or ceases to be, relevant to the learning task; thus, learners must detect and adapt to these changes accordingly. We survey existing work on feature drift adaptation with both explicit and implicit approaches. Additionally, we benchmark several algorithms and a naive feature drift detection approach using synthetic and real-world datasets. The results from our experiments indicate the need for future research in this area as even naive approaches produced gains in accuracy while reducing resources usage. Finally, we state current research topics, challenges and future directions for feature drift adaptation.

text: A survey on feature drift adaptation: Definition, benchmark, challenges and future directions Data stream mining is a fast growing research topic due to the ubiquity of data in several real-world problems. Given their ephemeral nature, data stream sources are expected to undergo changes in data distribution, a phenomenon called concept drift. This paper focuses on one specific type of drift that has not yet been thoroughly studied, namely feature drift. Feature drift occurs whenever a subset of features becomes, or ceases to be, relevant to the learning task; thus, learners must detect and adapt to these changes accordingly. We survey existing work on feature drift adaptation with both explicit and implicit approaches. Additionally, we benchmark several algorithms and a naive feature drift detection approach using synthetic and real-world datasets. The results from our experiments indicate the need for future research in this area as even naive approaches produced gains in accuracy while reducing resources usage. Finally, we state current research topics, challenges and future directions for feature drift adaptation.

year: 2017

title: The influence of group size on learning and problem-solving in New Zealand spotted wrasse (Notolabrus celidotus)

authors: Georgeson, Sean Alexander

abstract: Foraging dynamics are a fundamental ecological process influencing a variety of other important processes including population dynamics and reproduction. This study investigated the influence of group size on the foraging success of 40 New Zealand spotted wrasse (Notolabrus celidotus) using a problem-solving apparatus. A pilot study using four fish was initially carried out to test equipment and gain an understanding of the individual learning capacity of these fish. Following this pilot study, the full study was separated into four stages. Stage 1 involved observing individual fish attempting a problem-solving foraging task on their own. Stages 2 and 3 increased the group size of fish attempting this foraging task to two fish and four fish, respectively. Stage 4 involved individual fish attempting the task on their own, however, mirrors were fitted to the experimental tank to simulate an increase in group size. Results of this research showed that the presence/perceived presence of conspecifics resulted in increased success rates and reduced latency to solve the problem over time. These results suggest that group size is an important contributor to foraging efficiency in the New Zealand spotted wrasse, as larger groups outperformed smaller groups in most cases, and individual fish with simulated increases to group size outperformed individual fish without this effect. There are three potential explanations for these results. (1) The presence of conspecifics provides passive predator vigilance, enabling individual fish to put more time into solving the foraging task instead of scanning for predators. (2) As a function of increased competition for a limited resource, fish put more effort into solving the foraging task. (3) Social learning resulted in fish learning foraging strategies from conspecifics. It is likely that the effects of reduced predator vigilance and increased competition in larger group sizes influenced foraging success rates of the fish in this study concurrently. Additionally, the pair and group treatments displayed a reduced latency for fish to leave the starting arena and to orient toward the food reward than the other treatments. It is unlikely that these results can be attributed to increased chance due to increased fish density, as fish from the pair and group treatments performed similarly in weeks one and three, despite the group treatment having twice as many fish per trial. This indicates the potential effect of a social learning mechanism, such as local enhancement, in the spotted wrasse in this study. Future studies could further assess the influence of social learning through use of reliable demonstrator fish in an observer-demonstrator experiment. Further study is required to conclusively suggest whether the effect of reduced predator vigilance, increased competition, or social learning has a greater influence on increased foraging success with increased group size in New Zealand spotted wrasse.

text: The influence of group size on learning and problem-solving in New Zealand spotted wrasse (Notolabrus celidotus) Foraging dynamics are a fundamental ecological process influencing a variety of other important processes including population dynamics and reproduction. This study investigated the influence of group size on the foraging success of 40 New Zealand spotted wrasse (Notolabrus celidotus) using a problem-solving apparatus. A pilot study using four fish was initially carried out to test equipment and gain an understanding of the individual learning capacity of these fish. Following this pilot study, the full study was separated into four stages. Stage 1 involved observing individual fish attempting a problem-solving foraging task on their own. Stages 2 and 3 increased the group size of fish attempting this foraging task to two fish and four fish, respectively. Stage 4 involved individual fish attempting the task on their own, however, mirrors were fitted to the experimental tank to simulate an increase in group size. Results of this research showed that the presence/perceived presence of conspecifics resulted in increased success rates and reduced latency to solve the problem over time. These results suggest that group size is an important contributor to foraging efficiency in the New Zealand spotted wrasse, as larger groups outperformed smaller groups in most cases, and individual fish with simulated increases to group size outperformed individual fish without this effect. There are three potential explanations for these results. (1) The presence of conspecifics provides passive predator vigilance, enabling individual fish to put more time into solving the foraging task instead of scanning for predators. (2) As a function of increased competition for a limited resource, fish put more effort into solving the foraging task. (3) Social learning resulted in fish learning foraging strategies from conspecifics. It is likely that the effects of reduced predator vigilance and increased competition in larger group sizes influenced foraging success rates of the fish in this study concurrently. Additionally, the pair and group treatments displayed a reduced latency for fish to leave the starting arena and to orient toward the food reward than the other treatments. It is unlikely that these results can be attributed to increased chance due to increased fish density, as fish from the pair and group treatments performed similarly in weeks one and three, despite the group treatment having twice as many fish per trial. This indicates the potential effect of a social learning mechanism, such as local enhancement, in the spotted wrasse in this study. Future studies could further assess the influence of social learning through use of reliable demonstrator fish in an observer-demonstrator experiment. Further study is required to conclusively suggest whether the effect of reduced predator vigilance, increased competition, or social learning has a greater influence on increased foraging success with increased group size in New Zealand spotted wrasse.

year: 2020

title: The discovery of the Waiorongomai goldfield in 1881

authors: Hart, Philip

abstract: The first reports of gold being found in the vicinity of the Waiorongomai Stream were made in early November 1880, and after the opening of the goldfield a small rush took place to this part of the mountain. The first claims were pegged out in December and the following January, encouraged by some gold being found, but few claims were registered, for most prospectors were quickly disappointed. Prospecting was difficult because of the rugged terrain and heavy bush, and interest quickly faded.
Then, in early October, Hone Werahiko announced his latest and best find and provided samples of payable ore taken from a large reef. Immense excitement ensued, as this was the first payable reef to be found, and after Werahiko led miners on an exhausting trip to his ‘New Find’ a rush set in and many claims were pegged out. The first official to inspect the ground anticipated that the reefs could be easily worked, once an access track was constructed. The small settlement of Te Aroha was revived because a real goldfield had been found, at last.

text: The discovery of the Waiorongomai goldfield in 1881 The first reports of gold being found in the vicinity of the Waiorongomai Stream were made in early November 1880, and after the opening of the goldfield a small rush took place to this part of the mountain. The first claims were pegged out in December and the following January, encouraged by some gold being found, but few claims were registered, for most prospectors were quickly disappointed. Prospecting was difficult because of the rugged terrain and heavy bush, and interest quickly faded.
Then, in early October, Hone Werahiko announced his latest and best find and provided samples of payable ore taken from a large reef. Immense excitement ensued, as this was the first payable reef to be found, and after Werahiko led miners on an exhausting trip to his ‘New Find’ a rush set in and many claims were pegged out. The first official to inspect the ground anticipated that the reefs could be easily worked, once an access track was constructed. The small settlement of Te Aroha was revived because a real goldfield had been found, at last.

year: 2016