Recent evidence points to the importance of global operations across spatia
l regions larger than individual cortical receptive fields. Studies of cont
our integration and motion trajectory detection suggest that network operat
ions between local detectors underlie the encoding of extended contours in
space and extended trajectories in motion. Here we ask whether such network
operations also occur between second-order-detectors known to exist in vis
ual cortex. We compared performance for stimuli composed of either first-or
der or second-order elements equated for visibility, and we show that unlik
e the first-order case, there is little or no linking interaction between l
ocal second-order detectors. Near chance performance was found for elements
defined by second-order attributes when observers had to identify either a
n elongated spatial contour or an extended motion trajectory embedded in no
ise elements. This implies that the network operations thought to underlie
these two global tasks receive, at best, an impoverished input from local d
etectors that encode second-order image attributes. (C) 2000 Published by E
lsevier Science Ltd. All rights reserved.