88,737 research outputs found
Frontoparietal action-oriented codes support novel task set implementation
A key aspect of human cognitive flexibility concerns the ability to rapidly convert complex symbolic instructions into novel behaviors. Previous research proposes that this fast configuration is supported by two differentiated neurocognitive states, namely, an initial declarative maintenance of task knowledge, and a progressive transformation into a pragmatic, action-oriented state necessary for optimal task execution. Furthermore, current models predict a crucial role of frontal and parietal brain regions in this transformation. However, direct evidence for such frontoparietal formatting of novel task representations is still lacking. Here, we report the results of an fMRI experiment in which participants had to execute novel instructed stimulus-response associations. We then used a multivariate pattern-tracking procedure to quantify the degree of neural activation of instructions in declarative and procedural representational formats. This analysis revealed, for the first time, format-unique representations of relevant task sets in frontoparietal areas, prior to execution. Critically, the degree of procedural (but not declarative) activation predicted subsequent behavioral performance. Our results shed light on current debates on the architecture of cognitive control and working memory systems, suggesting a contribution of frontoparietal regions to output gating mechanisms that drive behavior
Stream VByte: Faster Byte-Oriented Integer Compression
Arrays of integers are often compressed in search engines. Though there are
many ways to compress integers, we are interested in the popular byte-oriented
integer compression techniques (e.g., VByte or Google's Varint-GB). They are
appealing due to their simplicity and engineering convenience. Amazon's
varint-G8IU is one of the fastest byte-oriented compression technique published
so far. It makes judicious use of the powerful single-instruction-multiple-data
(SIMD) instructions available in commodity processors. To surpass varint-G8IU,
we present Stream VByte, a novel byte-oriented compression technique that
separates the control stream from the encoded data. Like varint-G8IU, Stream
VByte is well suited for SIMD instructions. We show that Stream VByte decoding
can be up to twice as fast as varint-G8IU decoding over real data sets. In this
sense, Stream VByte establishes new speed records for byte-oriented integer
compression, at times exceeding the speed of the memcpy function. On a 3.4GHz
Haswell processor, it decodes more than 4 billion differentially-coded integers
per second from RAM to L1 cache
VXA: A Virtual Architecture for Durable Compressed Archives
Data compression algorithms change frequently, and obsolete decoders do not
always run on new hardware and operating systems, threatening the long-term
usability of content archived using those algorithms. Re-encoding content into
new formats is cumbersome, and highly undesirable when lossy compression is
involved. Processor architectures, in contrast, have remained comparatively
stable over recent decades. VXA, an archival storage system designed around
this observation, archives executable decoders along with the encoded content
it stores. VXA decoders run in a specialized virtual machine that implements an
OS-independent execution environment based on the standard x86 architecture.
The VXA virtual machine strictly limits access to host system services, making
decoders safe to run even if an archive contains malicious code. VXA's adoption
of a "native" processor architecture instead of type-safe language technology
allows reuse of existing "hand-optimized" decoders in C and assembly language,
and permits decoders access to performance-enhancing architecture features such
as vector processing instructions. The performance cost of VXA's virtualization
is typically less than 15% compared with the same decoders running natively.
The storage cost of archived decoders, typically 30-130KB each, can be
amortized across many archived files sharing the same compression method.Comment: 14 pages, 7 figures, 2 table
The Effect of Multiple Formats on Understanding Complex Visual Displays
Provides pedagogical insight concerning the skill of contours The resource being annotated is: http://www.dlese.org/dds/catalog_DLESE-000-000-004-595.htm
The Effect of Multiple Formats on Understanding Complex Visual Displays
Students in introductory science courses frequently have difficulty comprehending complex graphics such as contour maps. Computer-assisted instruction (CAI), because of its ability to convey the same information in different formats, may help students gain necessary graphic interpretation skills. This article describes a research project in which students practiced reading two temperature maps in either a standard black and white contour or a color-enhanced contour format. They were then divided into groups and tested using only standard contour maps. The tests examined comprehension of the distribution of sea surface temperature, oceanographic phosphate concentration, and brain activation. Results suggest that having students practice with differently formatted maps of the same information improves later comprehension of standard contour maps. Educational levels: Graduate or professional
Crossing MGLS with the Middle Grades Research Agenda: A Guide for Researchers
For the past several years, leaders in middle grades education research have strengthened their call for more methodologically robust quantitative research to address important questions in the field. Recently, two important routes towards addressing this call have emerged: the Middle Grades Longitudinal Study from the National Center for Education Statistics, and a new research agenda from the Middle Level Education Research Special Interest Group of the American Educational Research Association. In this paper, we conduct a content analysis of the items in the forthcoming longitudinal study in light of the extant research agenda. Results indicate that research questions in eight sections of the agenda are moderately to well-addressed by the data, and that the longitudinal study will provide rich contextual data related to many others. The concurrent emergence of the research agenda and this data offers an opportunity for the research community to engage in high-level quantitative research with a middle grades lens to inform future policy. The item-by-item crosswalk available for download (scroll down for link below) provides guidance for researchers using the Middle Grades Longitudinal Study data to address questions from the research agenda
Reasoning on transition from manipulative strategies to general procedures in solving counting problems
We describe the procedures used by 11- to 12-year-old students for solving basic counting problems in order to analyse the transition from manipulative strategies involving direct counting to the use of the multiplication principle as a general procedure in combinatorial problems.
In this transition, the students sometimes spontaneously use tree diagrams and sometimes use numerical thinking strategies. We relate the findings of our research to recent research on the representational formats on the
learning of combinatorics, and reflect on the didactic implications of these investigations
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