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Abstract:
Temporal patterning of stimuli can affect performance and be critical for perceptual learning. We tested whether trial history can explain target detection time even when target occurrence is unpredictable.
12 volunteers were presented with streams of stimuli of variable color, shape, and motion direction, and had to attend to all stimulus dimensions simultaneously to report Poisson-determined, 1-back repetitions in either dimension.
Response times decreased exponentially with the number of successive targets (group means for 1 to 4 targets in succession: 1050, 763, 717, 722 milliseconds; 2-way repeated measures ANOVA: F(3,33) = 195, pamp;amp;lt;amp;amp;lt;0.0001, no main effect of stimulus dimension but interaction between dimension and number of successive targets: F(6,66) = 5.11, pamp;amp;lt;0.001). Response times were well explained by a leaky integrator of trial history with fast exponential decay (half-life = 1.21 trials; correlation coefficients significant at pamp;amp;lt;0.0002 for all dimensions and subjects; group mean correlation coefficients for color, shape and motion targets: 0.57(0.03), 0.57(0.02), 0.47(0.03)).
Our results show that target detection times can be altered by trial history, and explainable by a fast-decaying integration of trial history. We propose that trial history modulates attention resulting in response time changes; we are currently investigating this hypothesis using functional neuroimaging.
