Abstract
We tested whether fast flicker can capture attention using eight flicker frequencies from 20–96 Hz, including several too high to be perceived (>50 Hz). Using a 480 Hz visual display rate, we presented smoothly sampled sinusoidal temporal modulations at: 20, 30, 40, 48, 60, 69, 80, and 96 Hz. We first established flicker detection rates for each frequency. Performance was at or near ceiling until 48 Hz and dropped sharply to chance level at 60 Hz and above. We then presented the same flickering stimuli as pre-cues in a visual search task containing five elements. Flicker location varied randomly and was therefore congruent with target location on 20% of trials. Comparing congruent and incongruent trials revealed a very strong congruency effect (faster search for cued targets) for all detectable frequencies (20–48 Hz) but no effect for faster flicker rates that were detected at chance. This pattern of results (obtained with brief flicker cues: 58 ms) was replicated for long flicker cues (1000 ms) intended to allow for entrainment to the flicker frequency. These results indicate that only visible flicker serves as an exogenous attentional cue and that flicker rates too high to be perceived are completely ineffective.
Highlights
We tested whether fast flicker can capture attention using eight flicker frequencies from 20–96 Hz, including several too high to be perceived (>50 Hz)
An analysis of variance (ANOVA) on mean correct RT was conducted with cue congruency and flicker frequency as within subject variables
The ANOVA yielded no significant main effect of temporal frequency F(2, 27) = 0.83, p = 0.447, but a significant effect of cue congruency F(1, 27) = 42, p < 0.0001. Most relevant for this experiment, there was a significant interaction between cue congruency and flicker frequency F(2, 27) = 3.6, p = 0.04, confirming again that the congruency effect depends on temporal frequency, as in Experiment 1, and that it occurs over the narrower range tested in Experiment 2
Summary
We tested whether fast flicker can capture attention using eight flicker frequencies from 20–96 Hz, including several too high to be perceived (>50 Hz). Comparing congruent and incongruent trials revealed a very strong congruency effect (faster search for cued targets) for all detectable frequencies (20–48 Hz) but no effect for faster flicker rates that were detected at chance. This pattern of results (obtained with brief flicker cues: 58 ms) was replicated for long flicker cues (1000 ms) intended to allow for entrainment to the flicker frequency. The authors accounted for this in terms of the invisible flickering stimulus entraining neural oscillations at the same frequency in visual cortex Their rationale was that this would benefit attentional selection because gamma-band (~30–70 Hz) oscillations in neural activity are observed when observers do top-down attentional tasks.
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