Precision in visual working memory reaches a stable plateau when individual item limits are exceeded.
Multiple studies have demonstrated that resolution in working memory (WM) declines as the number of stored items increases. Discrete-resource models predict that this decline should reach a stable plateau at relatively small set sizes because item limits prevent additional information from being encoded into WM at larger set sizes. By contrast, flexible-resource models predict that the monotonic declines in precision will continue indefinitely as set size increases and resources are distributed without any fixed item limit. In the present work, we found that WM resolution exhibited monotonic declines until set size reached three items, after which resolution achieved a clear asymptote. Moreover, analyses of individual differences showed a strong correlation between each observer's item limit and the set size at which WM resolution achieved asymptote. These behavioral observations were corroborated by measurements of contralateral delay activity (CDA), an event-related potential waveform that tracks the number of items maintained during the delay period. CDA activity rose monotonically and achieved asymptote at a set size that predicted individual WM capacity. Moreover, this neural measure of on-line storage also predicted the set size at which mnemonic resolution reached a stable plateau for each observer. Thus, independent behavioral and neural measures of WM capacity support a clear prediction of discrete-resource models. Precision in visual WM reaches asymptote when individual item limits are exceeded.
Department of Psychology, University of Oregon, Eugene, Oregon 97403, USA.
David E
DE
Anderson
Edward K
EK
Vogel
Edward
E
Awh
D001288:Attention / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D004594:Electrophysiology; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009949:Orientation / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
J Exp Psychol Hum Percept Perform. 2009 Oct;35(5):1359-67
19803642
Trends Cogn Sci. 2001 Mar 1;5(3):119-126
11239812
J Cogn Neurosci. 2001 Aug 15;13(6):766-85
11564321
Nature. 2008 May 8;453(7192):233-5
18385672
Science. 2008 Aug 8;321(5890):851-4
18687968
Cognition. 2010 Oct;117(1):69-79
20659731
Nature. 2005 Nov 24;438(7067):500-3
16306992
Spat Vis. 1997;10(4):433-6
9176952
Psychon Bull Rev. 2009 Aug;16(4):641-7
19648446
Nature. 2006 Mar 2;440(7080):91-5
16382240
Arch Gen Psychiatry. 2010 Jun;67(6):570-7
20530006
Nature. 2004 Apr 15;428(6984):751-4
15085133
Psychol Sci. 2007 Jul;18(7):622-8
17614871
J Neurosci. 2009 Dec 2;29(48):15258-65
19955378
Cortex. 2007 Jan;43(1):77-94
17334209
Neuroscience. 2006 Apr 28;139(1):23-38
16324795
J Vis. 2004 Dec 29;4(12):1120-35
15669916
Nature. 1997 Nov 20;390(6657):279-81
9384378
Cogn Psychol. 1997 Jun;33(1):64-87
9212722
J Neurosci. 2008 Apr 16;28(16):4183-91
18417697
Spat Vis. 1997;10(4):437-42
9176953
Nature. 2009 Apr 2;458(7238):632-5
19225460
Psychol Sci. 2009 Feb;20(2):207-14
19170936
Science. 1995 Mar 10;267(5203):1512-5
7878473
Proc Natl Acad Sci U S A. 2008 Apr 22;105(16):5975-9
18420818
Cogn Affect Behav Neurosci. 2005 Jun;5(2):144-55
16180621
J Vis. 2009 Sep 09;9(10):7.1-11
19810788
Nature. 2004 Apr 15;428(6984):748-51
15085132
J Exp Psychol Hum Percept Perform. 1998 Dec;24(6):1656-74
9861716
Psychon Bull Rev. 2010 Oct;17(5):673-9
21037165