Millisecond Forums

Sean,

Thank you for the pointer. I was thinking of masking but then got lost exploring the story behind my hardware limitations. :-) I'm on sabbatical at the moment so I'm endulding myself in distractions a bit. :-)

Regards

Jason

Dave,

Thanks for that very thorough explanation. I was pretty sure that I was running up against hardware limitations and you have helped me verify that assumption. Thanks again for an extremely helpful, and super quick, reply. 

Jason

Hi Jason,
Due to the limitations of displays that Dave mentions, researchers seeking to achieve subliminal presentations typically use "masking" - i.e. presenting another mask stimulus immediately before and/or after the target stimulus such that the forward mask is overwritten by the target stimulus, which is then overwritten by the backward mask. By sandwiching the target as such, you can present it for longer durations (17-50ms depending on the masks and stimuli) without it being consciously perceptible. This gives automatic neural circuitry more exposure to the stimulus without conscious circuits getting involved.
-Sean

The effective duration will depend on your display's refresh rate. To be able to achieve 10ms, you'd need your display running at 100Hz, which translates to a refresh cycle / display frame duration of exactly 10ms. On a display running at a lower rate, you cannot achieve 10ms. At 60Hz, you'd get a minimum duration of 16.7ms for a single frame, at 50Hz you end up at 20ms as the minimum. To go below 10ms, you of course need a display that refreshes even faster (e.g. 120Hz).

Those values are rough approximations, in reality the actual duration depends on a host of other physical characteristics of the respective display, see e.g. Plant, Hammond & Turner (Behavior Research Methods, 2004), Wiens et al. (Psychological Science, 2004), Plant & Turner (Behavior Research Methods, 2009), Elze & Tanner (Medical Physics, 2009), and http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012792