Adaptation of Saccades and Perceived Size after Trans-Saccadic Changes of Object Size

Abstract

When saccadic eye movements consistently fail to land on the intended target, saccade accuracy is maintained by gradually adapting the amplitude of successive saccades to the same target. Such saccadic adaptation is usually induced by systematically displacing a small visual target during the execution of the saccade. However, saccades are normally performed to extended objects. Here we report changes in saccade amplitude when the size of a target object is systematically changed during a saccade. Moreover, we find that this manipulation also affected the visual perception of the size of that object. Human subjects were tested in shortening and lengthening adaptation where they had to make saccades to targets of different sizes, which were each shortened or lengthened during saccade execution, respectively. In both experiments, a preadaptation and postadaptation phase required manually indicating the horizontal size of each target by grip aperture and, in a further experiment, a verbal size report. We evaluated the effect of change in visual perception on saccade and on the two modalities of judgment. We observed that (1) saccadic adaptation can be induced by modifying target object size and (2) this gradual change in saccade amplitude in the direction of the object size change evokes a concomitant change in perceived object size. These findings suggest that size is a relevant signal for saccadic system and its trans-saccadic manipulation entails considerable changes at multiple levels of sensorimotor performance.

The cost of making an eye movement: A direct link between visual working memory and saccade execution

“…However, it is currently unclear whether the presaccadic visual input is stored or that a prediction of postsaccadic visual input is made and stored prior to the saccade. Several studies on transsaccadic learning have, by inducing changes to saccade targets during the saccade, shown that observers could be taught to associate different presaccadic images with postsaccadic visual input (Bosco et al, 2015;Herwig et al, 2015;Valsecchi & Gegenfurtner, 2016). These studies provide evidence for the account that what was stored in VWM is, at least partly, a prediction of upcoming retinal input.…”

“…For example, after the saccade has been completed, the postsaccadic visual input can be integrated with the visual input stored in VWM to estimate saccade accuracy and increase the precision of information that is processed by the visual system (Ganmor, Landy, & Simoncelli, 2015;Oostwoud Wijdenes, Marshall, & Bays, 2015;Wolf & Schütz, 2015). Other possible mechanisms include transsaccadic learning, as several authors have shown that transsaccadic changes of stimuli (e.g., shape and spatial frequency) can alter how observers respond to presaccadic retinal stimuli (Bosco, Lappe, & Fattori, 2015;Herwig, Weiß, & Schneider, 2015;Valsecchi & Gegenfurtner, 2016). Transsaccadic learning is thought to occur because the visual system learns to associate presaccadic peripheral visual input and postsaccadic foveal visual input over the course of many saccades (Weiß, Schneider, & Herwig, 2014).…”

Prediction shapes peripheral appearance

“…In our daily life we continuously move our gaze toward objects that we want to scrutinize, and one could argue that the main function of peripheral vision is to guide foveal selection rather than to support perception. Albeit speculative, one alternative way of looking at this phenomenon is to consider it one result of the predictive mechanisms that supplement the impoverished representation of our peripheral visual field, along with foveal-to-peripheral extrapolation (Otten et al, 2016;Toscani et al, 2017) and transsaccadic learning (Bosco et al, 2015;Herwig, 2015;Herwig et al, 2015;Valsecchi & Gegenfurtner, 2016;Weiß et al, 2014). The predictive nature of peripheral vision might subsume other phenomena such as the tendency to show liberal criteria for detecting peripheral targets (Solovey, Graney, & Lau, 2015) and the tendency to be overconfident in peripheral perceptual judgments (Li, Lau, & Odegaard, 2018;Odegaard, Chang, Lau, & Cheung, 2018).…”

“…It seems plausible to assume that the tendency to perceive sharp and straight edges in the periphery originates in our experience of foveal vision. We know that peripheral appearance can be influenced by learned associations between peripheral and foveal stimulation (Bosco et al, 2015;Herwig et al, 2015;Valsecchi & Gegenfurtner, 2016). Nonetheless, specific experiments will be needed to prove that this is the case.…”

“…Despite this pervasive anisotropy in our visual system, we do not continuously experience dramatic changes in the appearance of our visual world as we move our eyes. A number of mechanisms contribute to this impression of continuity, including the integration of pre-and postsaccadic information (Ganmor, Landy, & Simoncelli, 2015;Herwig, 2015;Wolf & Schütz, 2015), transsaccadic learning of the association between peripheral and central appearance (Bosco, Lappe, & Fattori, 2015;Herwig, Weiß, & Schneider, 2015;Valsecchi & Gegenfurtner, 2016;Weiß, Schneider, & Herwig, 2014), and extrapolation of foveal content to the peripheral visual field (Otten, Pinto, Paffen, Seth, & Kanai, 2016; Citation: Valsecchi, M., Koenderink, J., van Doorn, A., & Gegenfurtner, K. R. (2018). Prediction shapes peripheral appearance.…”