Chunks in expert memory: Evidence for the magical number four… or is it two?

This study aims to test the divergent predictions of the chunking theory (Chase & Simon, 1973) and template theory (Gobet & Simon, 1996a; 2000) with respect to the number of chunks held in visual short-term memory and the size of chunks used by experts. We presented game and random chessboards in both a copy and a recall task. In a within-subject design, the stimuli were displayed using two presentation media: (a) physical board and pieces, as in Chase and Simon’s (1973) study; and (b) a computer display, as in Gobet and Simon’s (1998) study. Results show that, in most cases, no more than three chunks were replaced in the recall task, as predicted by template theory. In addition, with game positions in the computer condition, Masters replaced very large chunks (up to 15 pieces), again in line with template theory. Overall, the results suggest that the original chunking theory overestimated short-term memory capacity and underestimated the size of chunks used, in particular with Masters. They also suggest that Cowan’s (2001) proposal that STM holds four chunks may be an overestimate

The Alaska Marriage Amendment: The People’s Choice on the Last Frontier

I Sverige beräknas 17 % av befolkningen ha en hörselnedsättning, vilket innebär att det är den vanligaste sensoriska funktionsnedsättningen. Idag finns det en mängd studier som visar att hörselnedsättning är relaterat till sämre psykisk hälsa. Acceptans av sin hörselnedsättning har visat sig vara positivt för hörselnedsatta och samvarierar med hjälpsökande. Acceptance and commitment therapy (ACT) är en transdiagnostisk behandling där psykopatologi antas bero på en hög grad av upplevelsemässigt undvikande och fusion med tankar. Målet i ACT är att öka psykologisk flexibilitet där acceptans är en betydande komponent. Denna explorativa studie undersökte förändringsprocesser i ACT för personer med hörselnedsättning där utfallet var känslomässig och social anpassning för hörselnedsättningen (HHIE-S). De förändringsprocesser som prövades var acceptans (HAQ), som tidigare visat på medierande effekt för ACT, samt två alternativa förändringsprocesser; self-efficacy (HSE-4) och upplevd stress (PSS-4). Behandlingen bestod av åtta internetadministrerade moduler givna med behandlarstöd där veckovisa mätningar av förändringsprocesser och utfall användes. Studiens resultat visar att behandlingsgruppen upplevde marginellt signifikant mindre problem med känslomässig och social anpassning för hörselnedsättningen (HHIE-S). Studiens resultat pekar på att hörselrelaterad acceptans (HAQ) och self- efficacy (HSE-4) medierar behandlingens effekt på deltagarnas känslomässiga och sociala anpassning för hörselnedsättning (HHIE-S). Således tillför denna studie ytterligare belägg för acceptans som förändringsprocess i ACT. Även self-efficacy kan vara en intressant mediator att beakta i fortsatt forskning.

Finding a closest point in a lattice of Voronoi's first kind

We show that for those lattices of Voronoi's first kind with known obtuse superbasis, a closest lattice point can be computed in $O(n^4)$ operations where $n$ is the dimension of the lattice. To achieve this a series of relevant lattice vectors that converges to a closest lattice point is found. We show that the series converges after at most $n$ terms. Each vector in the series can be efficiently computed in $O(n^3)$ operations using an algorithm to compute a minimum cut in an undirected flow network

Soliton Solutions to the Einstein Equations in Five Dimensions

We present a new class of solutions in odd dimensions to Einstein's equations containing either a positive or negative cosmological constant. These solutions resemble the even-dimensional Eguchi-Hanson--(anti)-de Sitter ((A)dS) metrics, with the added feature of having Lorentzian signatures. They provide an affirmative answer to the open question as to whether or not there exist solutions with negative cosmological constant that asymptotically approach AdS$_{5}/\Gamma$, but have less energy than AdS$_{5}/\Gamma$. We present evidence that these solutions are the lowest-energy states within their asymptotic class.Comment: 9 pages, Latex; Final version that appeared in Phys. Rev. Lett; title changed by journal from original title "Eguchi-Hanson Solitons

Locally extracting scalar, vector and tensor modes in cosmological perturbation theory

Cosmological perturbation theory relies on the decomposition of perturbations into so-called scalar, vector and tensor modes. This decomposition is non-local and depends on unknowable boundary conditions. The non-locality is particularly important at second- and higher-order because perturbative modes are sourced by products of lower-oder modes, which must be integrated over all space in order to isolate each mode. However, given a trace-free rank-2 tensor, a locally defined scalar mode may be trivially derived by taking two divergences, which knocks out the vector and tensor degrees of freedom. A similar local differential operation will return a pure vector mode. This means that scalar and vector degrees of freedom have local descriptions. The corresponding local extraction of the tensor mode is unknown however. We give it here. The operators we define are useful for defining gauge-invariant quantities at second-order. We perform much of our analysis using an index-free `vector-calculus' approach which makes manipulating tensor equations considerably simpler.Comment: 13 pages. Final version to appear in CQ

M-Branes on k-center Instantons

We present analytic solutions for membrane metric function based on transverse $k$-center instanton geometries. The membrane metric functions depend on more than two transverse coordinates and the solutions provide realizations of fully localized type IIA D2/D6 and NS5/D6 brane intersections. All solutions have partial preserved supersymmetries.Comment: 22 pages, 5 figure