Purpose

• Visual subitising is the ability to quickly and intuitively enumerate small numbers of items, is hypothesized to be mediated by parallel processing.

• To examine any age-related variations in visual subitising performance.

• To understand how optical and neural changes with age1 affect visual performance

Methods

Visual Stimulus

• Task: To enumerate the number of dots as quickly & accurately as they could

• Response latency: the time it took to say the number into a microphone

• On each trial, a number (1-10) of black dots was presented on the monitor screen for 200 ms.

• Dot diameter: 3 arcmin• Randomly positioned in a 10 x 10 square (1◦ x 1◦)• Minimum dot distance ≥ 9’ (edge-to-edge)• Threshold: Midway between the upper & lower

asymptotes of a Weibull psychometric function.2 • 400 trials • Viewing was binocular

Subjects

• Normal macula, no lens & vitreous opacities …• Visual acuity: 20/20 or better

Stimulus duration (ms)

100 1000

Th

resh

old

(d

ots

)

0

2

4

6

8

10

KG (67)CB (74)MD (86)21-30

7.170.61251760-90

3.555.31071751-60

3.344.6671341-50

2.834.27101731-40

2.622.71091921-30

SD(yrs)

Mean age (yrs)

Gender (F)

Gender (M)

Sample size

Age group(yrs)

Decreasing Visual Subitising Performance with Age

Maya Kumar1, Roger Li1,2, Dennis Levi1,2, Sandy Chat1, & Manfred MacKeben3

1School of Optometry & 2Helen Wills Neuroscience Institute, University of California-Berkeley, Berkeley, California, USA

3The Smith-Kettlewell Eye Research Institute, San Francisco, California, USA

Poster #890

Results

Aging and Subitising

Optical or Neural?

Summary & Conclusions• Older people have problems processing multiple

objects at a time.

• Subitising, the quick assessment of small numbers of stimulus elements, is achieved through parallel processing. Such mechanisms are important where ever speed counts, e.g. in mobility and obstacle avoidance..

• Visual subitising performance deteriorates with advancing age.

• Mean subitising thresholds: Systematically decreased from 7.1 (21-30) to 4.8 dots (61-90) across the 5 age groups.

• Roughly, 50% of the loss in threshold occurred by the age of 62.

• The response latency (61-90) was prolonged an average of ~ 30% (the latency curve shifted upward for 1 - 7 dots).

• For all age groups, the mean number of dots reported was very close to the number of dots displayed on the screen.

• The loss in subitising performance cannot be explained by the optical changes.

• Subitising threshold (21-40-yr-old) was minimally affected by reduced retinal illumination (0.2 log unit) and optical blurring (with ‘plus’ lens ~20/20).

• After training, the performance (67-yr-old) was still worse when compared with 21-30 group

• With longer stimulus durations, counting performance (67-86-yr-old) could be improved to reach young adult level.

Acknowledgements

• The authors thank Jenny Sung for her help with collecting data.

• Research grants : NIH NEI R01EY01728 (DL) & The Smith-Kettlewell Eye Research Institute (MM)

References• Li RW, Edwards MH, Brown B. Vis. Res. 2000; 40: 3775-

3781. • Sharma V, Levi DM, Klein SA. Nat. Neurosci. 2000; 3:

496-501.

Reduced Ret. Illumination Optical blurring to 20/20

Slow Learning Stimulus Duration

Session

1 2 3 4 5 6 7

Th

resh

old

(d

ots

)

0

2

4

6

8

10KG (67)21-30

Threshold (dots)

10

Co

ntr

ol t

hre

sho

ld (

do

ts) 10

Opt. blur (20/20)RI: ND filter (0.2)

5

Age: 21-40n=5

Number of dots

0 2 4 6 8 10

Mea

n r

esp

on

se la

ten

cy (

ms)

1000 21-30 31-40 41-5051-6021-60 61-85

Number of dots

0 2 4 6 8 10

Mea

n h

it r

ate

(%)

0

20

40

60

80

100

21-30 31-40 41-5051-60> 60

Number of dots

0 2 4 6 8 10Mea

n n

um

ber

of

do

ts r

epo

rted

0

2

4

6

8

1021-30 31-40 41-5051-60> 60

Age (years)

Mea

n t

hre

sho

ld (

do

ts)

0

2

4

6

8

10

Age (years)

20 40 60 80

Th

resh

old

(d

ots

)

0

2

4

6

8

10F(4,78) =8.3P < 0.0001

Duration (ms) 200 100

Target Mask

SKERIT H E S M I T H – K E T T L E W E L L