The Effect of Attentional Cueing upon Speed Discrimination

Motion processes have often been regarded as being preattentive in nature. Additionally, in a few attention studies attempts have been made to incorporate the methodology common to classical psychophysics. Speed discrimination with multiple grating patches has been investigated with uncertainty/search paradigms (Verghese and Stone, 1995 Vision Research 35 2811 – 2823). Another method commonly used in attentional research is the cueing paradigm, which we have used here.

In this study participants had to discriminate, using a 2AFC method, whether one of four grating patterns moved faster or slower than the other patches (of a standard speed 6 deg s⁻¹). The speed of this test stimulus was altered from trial to trial with the use of an adaptive staircase procedure. Whilst the gratings were in motion a brief (32 ms) cue was presented. This could be either valid (58%), invalid (14%), or neutral (28%) in respect to the patch of grating which was moving at a different speed.

The results demonstrate that cueing had a strong effect upon the discrimination judgement. The invalid trials had up to a factor of four increase in discrimination thresholds when compared to the valid trials. Further experiments with post-stimulus cueing suggested that a decision theory model may account for a large proportion of these cueing effects. This is in agreement with similar cueing studies (Kinchla et al, 1995 Perception & Psychophysics 57 441 – 450) in which participants discriminated between different array elements.