Anytime collaborative brain–computer interfaces for enhancing perceptual group decision-making

In this paper we present, and test in two realistic environments, collaborative Brain-Computer Interfaces (cBCIs) that can significantly increase both the speed and the accuracy of perceptual group decision-making. The key distinguishing features of this work are: (1) our cBCIs combine behavioural, physiological and neural data in such a way as to be able to provide a group decision at any time after the quickest team member casts their vote, but the quality of a cBCI-assisted decision improves monotonically the longer the group decision can wait; (2) we apply our cBCIs to two realistic scenarios of military relevance (patrolling a dark corridor and manning an outpost at night where users need to identify any unidentified characters that appear) in which decisions are based on information conveyed through video feeds; and (3) our cBCIs exploit Event-Related Potentials (ERPs) elicited in brain activity by the appearance of potential threats but, uniquely, the appearance time is estimated automatically by the system (rather than being unrealistically provided to it). As a result of these elements, in the two test environments, groups assisted by our cBCIs make both more accurate and faster decisions than when individual decisions are integrated in more traditional manners.

Differential Brain Response to Metrical Accents in Isochronous Auditory Sequences

Even within equitonal isochronous sequences, listeners report perceiving differences among the tones, reflecting some grouping and accenting of the sound events. In a previous study, we explored this phenomenon of �subjective rhythmization� physiologically through brain event-related potentials (ERPs). We found differences in the ERP responses to small intensity deviations introduced in different positions of isochronous sequences, even though all sound events were physically identical. These differences seemed to follow a binary pattern, with larger amplitudes in the response elicited by deviants in odd-numbered than in even-numbered positions. The experiments reported here were designed to test whether the differences observed corresponded to a metrical pattern, by using a similar design in sequences of a binary (long-short) or a ternary (long-short-short) meter. We found a similar pattern of results in the binary condition, but a significantly different pattern in the ternary one. Importantly, the amplitude of the ERP response was largest in positions corresponding to strong beats in all conditions. These results support the notion of a binary default metrical pattern spontaneously imposed by listeners, and a better processing of the first (accented) event in each perceptual group. The differences were mainly observed in a late, attention-dependent component of the ERPs, corresponding to rather high-level processing.

Which brain mechanism cannot count beyond four?

Cowan makes an intriguing case for a fundamental limit in the number of chunks that can be stored in short term memory (STM). Chunks are collections of concepts that have strong associations to one another and much weaker associations to other chunks. A translation of this definition for the visual domain would be that a visual chunk is a collection of features that belong to the same perceptual group (see also Mahoney & Ullman 1988). Here, we will first address the neuronal mechanisms that may demarcate visual chunks. Then we critically evaluate to what extent these mechanisms might be responsible for the limit on the number of chunks that can be held in STM. We conclude that the clarity with which the psychophysical data point to the number four is not matched by a similarly clear limit imposed by physiological mechanisms.

Movement and Proximity Constrain Miscombinations of Colour and Form

A relatively frequent error when reporting brief visual displays is to combine presented features incorrectly. It has been proposed that Gestalt grouping constrains such errors so that miscombined features tend to come from the same perceptual group. In three experiments it was examined whether this principle applies to grouping by motion, and to grouping by proximity. Miscombinations of colour and form were more likely to consist of a colour and form that had moved in the same direction than features which had moved in opposite directions. Miscombinations were also more likely for adjacent items. The implications of these results for the mechanisms of feature integration are discussed.