Breaking Down Bias
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1
University of Newcastle, Australia
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2
Institute of Cognitive Neuroscience and Psychology Research Centre for Natural Sciences, Hungary
Background: Mismatch negativity (MMN) is evoked when a sound deviates from a regularly recurring pattern. The system underlying MMN is hypothesized to subserve automatic relevance filtering with sounds conforming to predictable regularities eliciting minimal response preserving resources for sounds that violate predictions and prompt new learning. This study features the exploration of a bias in this system that indicates processing of the world around us is context driven rather than a direct reflection of environmental statistics.
Methods: The bias is revealed using a ‘multi-timescale’ sequence in which the MMN is elicited to a sequence of two sounds (a short and long tone) that alternate roles as a highly repetitive standard (p=0.875) and rare deviant (p=0.125). The roles of the two tones alternate in blocks at slow (2.4 minutes/4 blocks/480 tones) or fast rates (0.8 minutes/12 blocks/180 tones). In data from three studies there was an order dependent bias that manifested as MMN larger in size in the slow compared to fast changing sequences only for the tone encountered as deviant in the first block type. For the tone that is first encountered as a standard and later presented as a deviant, the MMN is the same size in both sequences. Here we compare MMN size at transition points in the sequence (first-half; immediately after change in roles) versus later in a block (second-half; when roles are established).
Results: The tone x speed bias previously observed was present in first-half data only and absent in second-half data. In the first half MMN to the long tone, the first encountered deviant was larger in the slow than fast blocks. The pattern for MMN to the short tone, the standard as a later deviant, reversed with fast larger than slow.
Discussion: The two tones were processed differently at the transition points only. This difference dissipated over the course of the entire block, as shown by no interaction or effect in second-half data. This difference in tone processing is reactivated each time a new block starts. In order to understand the bias, it is important to determine what is learnt through the adherence to first roles.
Keywords:
mismatch negativity (MMN),
Auditory Perception,
Memory,
oddball paradigm,
context effects
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Poster
Topic:
Memory
Citation:
Mullens
D,
Todd
J,
Winkler
I,
Damaso
K,
Provost
A,
Whitson
LR and
Heathcote
A
(2013). Breaking Down Bias.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00113
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Received:
24 Sep 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Mr. Daniel Mullens, University of Newcastle, Newcastle, Australia, daniel.mullens@uon.edu.au