For example, Spivey and Geng found that participants tend to re-fixate the spatial location of previously inspected stimuli, when they were questioned about visual details (i.e., color and orientation) in a subsequent recall task 11 Experiment 2. Such eye movements have been shown to reinstate the spatial layout of previously inspected images 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. When we recall detailed visual information from memory, we tend to move our eyes despite the fact that there is nothing to look at. This finding indicates that eye movements during imagery are subject to individual strategies, and the immersive setting in 3D space made individual differences more likely to unfold. We suggest that object visualizers rely less on spatial information because they tend to process and represent the visual information in terms of color and shape rather than in terms of spatial layout. Furthermore, we found that looking back to relevant locations depends on individual differences in visual object imagery abilities.
#Stimulus duration framen psychopy free
We show that participants also look back to relevant locations when they are free to move in 3D space. In the present study we used immersive virtual reality to investigate how individual tendencies to process and represent visual information contribute to eye fixation patterns in visual imagery of previously inspected objects in three-dimensional (3D) space. The reason for these differences remains unclear. Previous studies indicated that such eye movements are related to the spatial location of previously seen items on 2D screens, but they also showed that eye movement behavior varies significantly across individuals. As a result, on most cards, as long as frames are not being ‘dropped’ (see Detecting dropped frames) you can present stimuli for a fixed, reproducible period.During recall of visual information people tend to move their eyes even though there is nothing to see. Calls to Window.flip() will be synchronised to the frame refresh the script will not continue until the flip has occurred. The frame rate is extremely precise, much better than ms-precision. At 60Hz refresh you can not present your stimulus for, say, 120ms the frame period would limit you to a period of 116.7ms (7 frames) or 133.3ms (8 frames).Īs a result, the most precise way to control stimulus timing is to present them for a specified number of frames. It also might also give the false impression that a stimulus can be presented for any given period. An error of 16.7ms might be acceptable to long-duration stimuli, but not to a brief presentation. So using this method you get timing accurate to the nearest frame period but with little consistent precision. Alternatively, if the time has reached 2.001s, there will not be an extra frame drawn. If the screen is refreshing at 60Hz (16.7ms per frame) and the getTime() call reports that the time has reached 1.999s, then the stimulus will draw again for a frame, in accordance with the while loop statement and will ultimately be displayed for 2.0167s. In the above, the stimulus does not actually get drawn for exactly 0.5s (500ms).
flip ()Ĭlocks are accurate to around 1ms (better on some platforms), but using them to time stimuli is not very accurate because it fails to account for the fact that one frame on your monitor has a fixed frame rate. phase += 0.1 # Increment by 10th of cycle win. getTime () < 2.0 : # Clock times are in seconds if 0.5 <= clock. autoLog = False # Or we'll get many messages about phase change # Let's draw a stimulus for 2s, drifting for middle 0.5s clock = core. autoDraw = True # Automatically draw every frame gabor. GratingStim ( win, tex = 'sin', mask = 'gauss', sf = 5, name = 'gabor' ) gabor. From psychopy import visual, core # Setup stimulus win = visual.
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