Qualtrics Reaction Time Engine (QRTEngine) is an extension to Qualtrics which allows researchers, but generally any who are interested, to easily build behavioural online experiments.
There is a white flash between the presentation of stimuli, especially noticeable when the same stimulus is presented twice. This happens regardless of whether the stimulus is simple (just text) or complex (ie. an image).
The problem seems to lie in the asynchronous behaviour of the Engine. The display of a stimulus is virtually on it's own thread as opposed to the being 'marked' for display code. So if there's a significant delay between the hiding of a stimulus and the presentation of the next stimulus, the next stimulus might not be marked off as 'to be displayed' in time, so instead of 1 draw cycle going by, 2 go by. This means that for one frame, no stimulus is presented, which would explain the white flash.
There is a white flash between the presentation of stimuli, especially noticeable when the same stimulus is presented twice. This happens regardless of whether the stimulus is simple (just text) or complex (ie. an image).
The problem seems to lie in the asynchronous behaviour of the Engine. The display of a stimulus is virtually on it's own thread as opposed to the being 'marked' for display code. So if there's a significant delay between the hiding of a stimulus and the presentation of the next stimulus, the next stimulus might not be marked off as 'to be displayed' in time, so instead of 1 draw cycle going by, 2 go by. This means that for one frame, no stimulus is presented, which would explain the white flash.