Fig 1.
Dichoptic stimulation and colour calibration:
A. Illustration of a given trial in which dot stimuli are presented to the contralateral eye (the left eye in this example). Through the use of the coloured glasses, the green coloured stimuli are visible to the contralateral eye alone, which is red filtered. By contrast, the blind spot patch is presented to the ipsilateral eye alone, which is green filtered. The dichoptic stimuli are experienced by the participant as if they were presented to both eyes. The blind spot mask is not visible to the participant (because of the ipsilateral blind spot, assuming correct fixation). To facilitate fixation, fusion stimuli are presented above and below fixation cross to both eyes B. Illustration of the colour calibration paradigm, in which the participant is presented with six dots located radially above and below the fixation. The experimenter blocks each coloured lens at a time to adjust the luminance of red and green separately. The final values of red and green luminance are experienced dichoptically as dark colours while remaining invisible through the respective lens filter.
Fig 2.
The experimenter moves a test spot away from fixation along the horizontal axis until the participant reports the stimulus disappearing (i.e., to have entered their blind spot region). The experimenter then increases the width and height of the test spot until the participant’s blind spot is mapped (i.e., any further increase of the height or width of the stimulus would render it visible). The fixation cross changes colour whenever a broken fixation is recorded by the eye tracking equipment. The test spot should become visible when this happens (i.e., blind spot location shifts with gaze). The experiment continues once a fixation is recorded again. Note that while we represent the stimuli in black and white, the real task will use coloured stimuli and will be performed wearing the coloured glasses as shown in Fig 1A. This will allow us to present the stimuli monocularly to either eye depending on the blind spot mapping being performed.
Fig 3.
We illustrate two given trials over time (t) in which A. the foil is presented first (above blind spot) for 400 ms, followed by a simultaneous presentation of the foil (above blind spot) and target (spanning blind spot) for 400ms and a presentation of the target alone (spanning blind spot) for 400ms and B. the target is presented first (below blind spot) for 400 ms, followed by a simultaneous presentation of the target (below blind spot) and foil (above blind spot) for 400ms and a presentation of the foil alone (above blind spot) for 400ms. All trials end with a fixation stimulus change from ‘+’ to ‘x’ which cues for a response to the task. Participants’ response is to state which pair of dots had a smaller separation, the one appearing first or second. Note that while we represent the stimuli in black and white, the real task will be coloured and will be performed with the coloured glasses as shown in Fig 1A. This will allow us to present the stimuli either to the contralateral eye or ipsilateral eye.
Fig 4.
We illustrate two given trials over time (t) in which A. the foveal circle’s size starts smaller than the peripheral one and B. the foveal circle size starts larger than the peripheral one. Participants’ task is to adjust the foveal circle’s area to match the peripheral circle area. In all cases participants report their final size selection with a mouse click. The size of the fixation cross is randomised between trials to prevent local cues from biasing participants’ responses. Note that while we represent the stimuli in black and white here, the real task will involve coloured stimuli and will be performed with the coloured glasses as shown in Fig 1A. This will allow us to present the stimuli either to the contralateral eye or ipsilateral eye.
Fig 5.
All trials begin with the presentation of the blind spot shape and central cross until the fixation is maintained for at least 200 ms. We illustrate two given trials over time (t) in which a motion trace is A. presented around blind spot, appearing at locations 1 (darkest gray circle), 2, 3 and 4 (white circle; 100ms/location). Following this, the same motion trace is presented appearing at locations 4 (darkest gray circle), 3, 2, 1 (white circle; 100ms/location) before appearing again at locations 1, 2, 3 and 4 (100ms/location) and B. is presented above blind spot appearing at locations 1, 2, 3 and 4 (100ms/location). Following this, the same motion trace is presented appearing at locations 4 (darkest gray circle), 3, 2, 1 (white circle; 100ms/location) before appearing again at locations 1 (darkest gray circle), 2, 3 and 4 (white circle; 100ms/location). All trials end with a fixation stimulus change from ‘+’ to ‘x’ which cues for a response to the task. Participants’ task is to state whether that trial’s motion path was curved towards the left (towards the blind spot in the left hemifield, towards fixation in the right hemifield) or the right (towards the fixation in the left hemifield, towards the blind spot in the right hemifield). Note that while we represent the stimuli in black and white, the real task will be coloured and will be performed with the coloured glasses as shown in Fig 1A. This will allow us to present the stimuli at different locations to either the contralateral eye or ipsilateral eye.
Table 1.
Table of experimental predictions.
Fig 6.
Simulated data of the three theories with respect to experiment 2.a Simulated data of IIT, NREP and AI predictions with respect to the A. distance estimation task, B. area size task and C. motion curvature task. See Table 1 for a detailed description of these predictions. A sample of the code used to simulate the predicted data represented in the figures is available at: https://github.com/ClementAbb/Intrepid_2a_staircase_simulation/tree/master.