Psychological Science, Vol. 3, No. 6, November 1992

Perceptual Bias For Forward-Facing Motion

Michael K. McBeath, Kazunori Morikawa, and Mary K. Kaiser

Abstract

When an occluded horizontal row of shapes is shifted laterally, apparent motion can be experienced in either the leftward or rightward direction. Four experiments provide evidence when directionality was specified geometrically (e.g. triangles), next largest when specified biologically (e.g. mice), and absent when specified calligraphically (e.g. letter "R"). The bias increased parametrically as a function of triangle pointedness, and was consistent with the directional interpretation of an ambiguous duck-rabbit. The results confirm that cognitively-specified forward-facing orientation can influence experienced direction of motion.

Stimuli and Results, Experiment 2
Figure 1. Experimental Technique ^^^

Subjects were presented two-frame 
apparent motion using a laterally 
shifted row of shapes with a clearly 
specified forward-facing direction.

Figure 2. Stimuli and Results, Experiment 2.>>>

Six shapes in left-facing, neutral
and right-facing orientations,
and mean spatial offset required
to cancel out the forward-facing bias
(in percent stimulus spacing).
Results of Experiment 3 

Ambiguous Figure(Both Orientations)

 

Samples from 
Duck Set

 

Samples from
Rabbit Set

 Stimuli and Results of Experiment 4 <Both Orientations  
Grouped: 2.37%*  
(0.75%) 

 

<All 12 Priming  
Figures Grouped:  
<4.14%** (0.35%)
Figure 4. Results of Experiment 3.

Magnitude of forward-facing bias as a 
function of the horizontal angle (or pointedness) 
of laterally-aligned isosceles triangles.
Figure 5. Stimuli and Results, Experiment 4.

Both orientations of the ambiguous 
duck-rabbit plus two samples each from the 
unambiguous duck and rabbit priming sets. 
The ambiguous stimuli produced a bias 
consistent with the forward-facing 
direction of each priming set.

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