Under appropriate conditions an observer's memory for the final
position of an abruptly halted object is distorted in the direction of
the represented motion.
In a classic representational momentum
experiment, subjects are presented with a series of static inducing
displays sampled from a path of motion
(e.g. 3 rectangles at successive 17° rotations about the
rectangle's center), and instructed to remember the last position.
The subjects are then tested by asking them to decide if an additional
stimulus (e.g. a fourth rectangle), presented at either the same
orientation as the last inducing stimulus or slightly further
or back along the implied path, was in fact at the same orientation as
the last inducing display. Subjects are much less likely to reject
forward than backward distractors.
In the example simulation on this page, the test position is in fact
further along the path of motion than the last stimulus position!
The simulation above is implemented using
The Netscape 2.0 "animated GIF" feature. A version using
the constraints of raster displays and a network environment imply that timing
and positioning for the demonstration are less precise than in an actual
experiment. To maximize the momentum effect
given these inducing stimuli,
we would use stimulus durations of perhaps 250ms,
interstimulus intervals after first and second stimuli of perhaps 250ms,
and a retention interval before the test stimulus of about 300ms.
By the way, an inducing stimulus of 3 rotated rectangles
is not the most powerful way to produce RM. Try
motion of a directional (arrow-like) cartoon creature, e.g. a fish with
a big tail.
Copyright © 1995, Jennifer J. Freyd.
This demonstration was produced by