Perhaps unidimensional is not unidimensional

Miller (1956) identified his famous limit of 7 ± 2 items based in part on absolute identification—the ability to identify stimuli that differ on a single physical dimension, such as lines of different length. An important aspect of this limit is its independence from perceptual effects and its application across all stimulus types. Recent research, however, has identified several exceptions. We investigate an explanation for these results that reconciles them with Miller’s work. We find support for the hypothesis that the exceptional stimulus types have more complex psychological representations, which can therefore support better identification. Our investigation uses data sets with thousands of observations for each participant, which allows the application of a new technique for identifying psychological representations: the structural forms algorithm of Kemp and Tenenbaum (2008). This algorithm supports inferences not possible with previous techniques, such as multidimensional scaling

The hare and the tortoise: emphasizing speed can change the evidence used to make decisions

Decision-makers effortlessly balance the need for urgency against the need for caution. Theoretical and neurophysiological accounts have explained this tradeoff solely in terms of the quantity of evidence required to trigger a decision (the “threshold”). This explanation has also been used as a benchmark test for evaluating new models of decision making, but the explanation itself has not been carefully tested against data. We rigorously test the assumption that emphasizing decision speed versus decision accuracy selectively influences only decision thresholds. In data from a new brightness discrimination experiment we found that emphasizing decision speed over decision accuracy not only decreases the amount of evidence required for a decision but also decreases the quality of information being accumulated during the decision process. This result was consistent for 2 leading decision-making models and in a model-free test. We also found the same model-based results in archival data from a lexical decision task (reported by Wagenmakers, Ratcliff, Gomez, & McKoon, 2008) and new data from a recognition memory task. We discuss implications for theoretical development and applications

Need for closure is associated with urgency in perceptual decision-making

Constant decision-making underpins much of daily life, from simple perceptual decisions about navigation through to more complex decisions about important life events. At many scales, a fundamental task of the decision-maker is to balance competing needs for caution and urgency: fast decisions can be more efficient, but also more often wrong. We show how a single mathematical framework for decision-making explains the urgency/caution balance across decision-making at two very different scales. This explanation has been applied at the level of neuronal circuits (on a time scale of hundreds of milliseconds) through to the level of stable personality traits (time scale of years)

Gamelike features might not improve data

Many psychological experiments require participants to complete lots of trials in a monotonous task, which often induces boredom. An increasingly popular approach to alleviate such boredom is to incorporate gamelike features into standard experimental tasks. Games are assumed to be interesting and, hence, motivating, and better motivated participants might produce better data (with fewer lapses in attention and greater accuracy). Despite its apparent prevalence, the assumption that gamelike features improve data is almost completely untested. We test this assumption by presenting a choice task and a change detection task in both gamelike and standard forms. Response latency, accuracy, and overall task performance were unchanged by gamelike features in both experiments. We present a novel cognitive model for the choice task, based on particle filtering, to decorrelate the dependent variables and measure performance in a more psychologically meaningful manner. The model-based analyses are consistent with the hypothesis that gamelike features did not alter cognition. A postexperimental questionnaire indicated that the gamelike version provided a more positive and enjoyable experience for participants than the standard task, even though this subjective experience did not translate into data effects. Although our results hold only for the two experiments examined, the gamelike features we incorporated into both tasks were typical of—and at least as salient and interesting as those usually used by—experimental psychologists. Our results suggest that modifying an experiment to include gamelike features, while leaving the basic task unchanged, may not improve the quality of the data collected, but it may provide participants with a better experimental experience

Muon background studies for beam dump operation of the K12 beam line at CERN

In the scope of the Physics Beyond Colliders study at CERN a future operation of the NA62 experiment in beam dump mode is discussed, enabling the search for dark sector particles, e.g. heavy neutral leptons, dark photons and axions. For this purpose, the 400 GeV/c primary proton beam, extracted from the SPS, will be dumped on a massive dump collimator located in the front end of the K12 beam line. Muons originating from interactions and decays form a potential background for this kind of experiment. To reduce this background, magnetic sweeping within the beam line is employed. In this contribution, the muon production and transport has been investigated with the simulation framework G4beamline. The high computational expense of the muon production has been reduced by implementing sampling methods and parametrizations to estimate the amount of high-energy muons and efficiently study optimizations of the magnetic field configuration. These methods have been benchmarked with measured data, showing a good qualitative agreement. Finally, first studies to reduce the muon background by adapting the magnetic field configuration are presented, promising a potential background reduction by a factor four