PsychoPy is an application for the creation of experiments in behavioral science (psychology, neuroscience, linguistics, etc.) with precise spatial control and timing of stimuli. It now provides a choice of interface; users can write scripts in Python if they choose, while those who prefer to construct experiments graphically can use the new Builder interface. Here we describe the features that have been added over the last 10 years of its development. The most notable addition has been that Builder interface, allowing users to create studies with minimal or no programming, while also allowing the insertion of Python code for maximal flexibility. We also present some of the other new features, including further stimulus options, asynchronous time-stamped hardware polling, and better support for open science and reproducibility. Tens of thousands of users now launch PsychoPy every month, and more than 90 people have contributed to the code. We discuss the current state of the project, as well as plans for the future.

Eye movement analysis is an effective method for research on visual perception and cognition. However, recordings of eye movements present practical difficulties related to the cost of the recording devices and the programming of device controls for use in experiments. GazeParser is an open-source library for low-cost eye tracking and data analysis; it consists of a video-based eyetracker and libraries for data recording and analysis. The libraries are written in Python and can be used in conjunction with PsychoPy and VisionEgg experimental control libraries. Three eye movement experiments are reported on performance tests of GazeParser. These showed that the means and standard deviations for errors in sampling intervals were less than 1 ms. Spatial accuracy ranged from 0.7° to 1.2°, depending on participant. In gap/overlap tasks and antisaccade tasks, the latency and amplitude of the saccades detected by GazeParser agreed with those detected by a commercial eyetracker. These results showed that the GazeParser demonstrates adequate performance for use in psychological experiments.

We investigated the perceived locations of two stimuli flashed successively near the time of saccade execution in a dark room. The inter-stimulus interval (ISI) between the flashes ranged from 80 to 240 ms. The results show that when the ISI was 120 ms or shorter, perceived locations of the flashes interacted with each other so that the perceived distance between them was equal to the distance between these flashes on the retina. When the ISI was 240 ms, this interaction was weak. These results suggest two hypotheses. Firstly, the relation of retinal locations of flashes is a strong cue for perceiving the flash locations when the ISI is shorter than about 120 ms.Secondly, the process of perceiving or memorizing a flash location requires some time. Therefore, the perceived location of the succeeding flash affects that of the preceding flash when the ISI as shorter than about 120 ms.

Based on localization error for a single perisaccadic flash, eye position signal is supposed to change more slowly than physical eye position. Nevertheless, a flicker is not perceived as moving in accordance with localization error for a single flash. We carried out two experiments to investigate this problem. Experiment 1 examined how a single flash or a flicker presented before saccade was perceived. The results showed that the flicker was not perceived as moving, although mislocalization for the single flash increases gradually before saccade. Experiment 2 was a vernier test of two stimuli successively flashed before the saccade. The results showed that the point of subjective equality shifted in accordance with the mislocalization for a single perisaccadic flash when the interstimulus interval (ISI) was about 2 s; however, it did not shift when the ISI was 78 ms. Comparison between these results and previous studies suggests that the relation of the locations of successive flashes before saccade is perceived exocentrically when the ISI and stimulus onset asynchrony between flashes was short.

Recent studies have suggested that the apparent shape of a perceptually organized object flashed immediately before saccade is not distorted although a perisaccadic flash is mislocalized as if the visual space is compressed toward the goal of the saccade. We report that the apparent width of a Kanizsa illusory rectangle flashed in the perisaccadic period was compressed as much as that of a control stimulus that did not induce illusory rectangle, while that of a rectangle with real contour was less compressed. Our results imply that the process of saccadic compression of visual space completes faster than the interpolation process of illusory contours.