Peripheral vision and pattern recognition: a review - strasburger - main

Peripheral_Vision.doc
In an even more extensive study involving twenty healthy young observers, Strasburger, Gothe,
and Lutz (2001) compared contrast sensitivity for recognition to that for detection in a finelyspaced
raster covering the full central field with a 20-deg-radius. Detection stimuli were Gabor
patterns (1 cyc/deg, sigma 1.5 deg; discrimination of vertical vs. horizontal orientation was
taken as a measure of detection); recognition stimuli were as before the digits 0–9 at a height of
2.4 deg, the contrast thresholds of which were determined at 65 positions in a polar raster.
Overall, close to 100,000 observer responses were collected. Results are shown in Figure 15
and Figure 16. All subjects showed stable but inter-individually somewhat different sensitivity
surfaces. Contrast thresholds for detection and recognition increased in the mean linearly with
eccentricity out to 30° eccentricity, by 0.029 logC/° for Gabor patch detection and by 0.036
logC/° for character recognition. Recognition contrast thresholds were by 0.25 to 0.50 log units
higher than those for detection. There was some variation between subjects but less than
between conditions. No difference was observed between the left and right visual field. Again
there was a performance plateau on the horizontal meridian between 15° and 20° (Figure 15b)
(Strasburger et al., 2001, Strasburger, 2003b).
Figure 14. Visual fields of recognition
and detection for one subject (CH).
Recognition fields (heavy lines) are
obtained from threshold-contrast-vs.-size
trade-off functions as shown in Figure
13. The form of the field is approximated
by ellipses. Each ellipse shows the
border of recognition at a given level of
contrast, at the values 1.2%, 2%, 3%,
4%, 6%, 10%, 30% starting from the
inner circle (contrast in Michelson units).
Note the performance plateau on the
horizontal meridian between 10° and 25°
(between the 3% and 4% line), similar to
the one found in perimetry (Harvey &
Pöppel, 1972; Pöppel & Harvey, 1973).
The 100%-contrast ellipse represents a
maximum field of recognition obtained
by extrapolation; its diameter is 46°×32°.
Also indicated in dashed lines are the
fields of light-spot detection in standard
static perimetry for the same subject.
(From Strasburger & Rentschler, 1996,
Fig. 4.)
44