Behaviors maintaining perceptual continuity

• Main Author: Lau, Wee Kiat
• Other Authors: Gerrit Maus
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Social sciences::Psychology
• Online Access: https://hdl.handle.net/10356/144248; https://doi.org/10.21979/N9/CBUORH; https://doi.org/10.21979/N9/4CZRBD
• Institution: Nanyang Technological University

Our perception of the world is continuous although the input to various senses is fraught with perturbations and ambiguities. Perceptual continuity is defined as the continuous experience of external, discriminable things which involves some implicit reasoning to complete missing information. In this thesis, we conducted psychophysical experiments to investigate behaviors that maintain perceptual continuity over three parts. In Part 1, we investigated response behaviors. Responses to a stimulus do not deviate from each other if the stimulus appeared stable and non-changing. We examined response behaviors through serial dependence. Serial dependence is an effect in which the current response error is biased by the preceding stimulus. We showed that our responses to visual stimulus can be biased (i.e. assimilate) to similar or stable objects. In the case of serial dependence, our responses to the physical world appear to be embedded in perception, and we become biased by what we previously perceived. In Part 2, we investigated how observers behaved if they were unaware to consistent changes. We do not notice changes which occur during eye blinks because of missing visual information. We introduced a dot stimulus which steps repeatedly during the blink and showed that the oculomotor system adapted to positional changes across blinks even though the observers were unaware of the changes. From this, we deduced that the oculomotor system could maintain perceptual continuity by blink adaptation behaviors: positional changes were minimized during the blink. Therefore, objects appear to be in the same position after the blink. Since the object appears to not have changed, the perception of the object’s position remains continuous. In Part 3, we studied how saccade planning is influenced by blinks and fixation errors. The oculomotor system plans the saccade before shifting our eyes to where we want them to. The saccade plan is updated when additional movements occur. This updating allows the oculomotor system to ensure our eyes land accurately at the destination. We asked if the saccade plan was also updated simply by blinking, since the eyes move during the blink. We found that saccades to visible objects were more accurate if observers blinked after saccade planning. This indicated that saccade plans were updated to enable a continuous experience of visual exploration because our eyes land where we want them to. In summary, this thesis addressed the following behaviors that could maintain perceptual continuity: 1) through serial dependence, we continue to respond in a similar way based on what we saw previously, 2) positional changes of a target are minimized across a blink, and 3) saccade plans are updated when we blink during visual exploration to visible targets. We then argued that these findings help explain how temporal stability ensures perception is continuous. Temporal stability may be achieved by expressing serial dependence which may be limited to vision. Within vision, temporal stability is not only a failure of change detection. Stability is achieved by recruiting the oculomotor system. The oculomotor system then uses a signal that anticipates eye positions after blinking to re-orient our eyes during blinks, or to update the saccade plans so that that our eyes land on the target.