The influence of flash characteristics on the visual and haptic flash-lag effect - research data from the 2012/2013 study.

Research Questions/Hypotheses:

The initial hypothesis of the study is the temporal sampling hypothesis of the FLE, according to which the short stimulus in the FLE paradigm triggers a supramodal higher process of position judgment, the starting time of which depends on the processing time of the short stimulus. This leads to the hypothesis of a high relevance of the sensory characteristics of the short stimulus for the magnitude of the FLE, and that a longer processing time of the short stimulus is associated with a larger FLE. We examined these hypotheses with respect to the modality of the short stimulus (Experiment 1) and with respect to the duration and intensity of the short stimulus in haptic FLE (Experiment 2).

Research Design:

Experimental design, Laboratory experiment; repeated measurements

Measurement Instruments/Apparatus:

Experiment 1: While participants observe periodic back-and-forth movements (visual object) or perform them with their right hand (haptic object), a short stimulus (=flash) is presented on the moving object, in the 3rd or 5th partial movement. Below the motion corridor was a stationary object, and Vpn judged whether the moving object was to the right or left of the stationary object when the brief stimulus was given. Four conditions were realized within each participant: The sensory modality of the brief stimulus (visual vs. haptic) and the sensory modalities of moving and stationary object (same modality as brief stimulus or both modalities, visual and haptic, simultaneously) were varied. The short stimulus started while the moving object was at one of seven positions relative to the stationary: -99, -66, -33, 0, 33, 66, 99 mm; the reciprocating motion started on the right or left. In each experimental block, for a single experimental condition, each combination of movement start position (2), short stimulus position (7), and partial movement with short stimulus (2) was presented twice (272*2 = 56 runs in random order). There were 3 blocks per experimental condition with short pauses in between. The order of the experimental conditions was balanced between Vpn according to Latin square. The experiment was conducted in 2 sessions of 2.5 h each; at the beginning of each session, the back-and-forth movement was practiced; at the beginning of the first sessions, 56 active movements of the participants were recorded, which were later reproduced as visual conditions.
For each experimental condition and each start position of the brief stimulus, the number of times the moving object was perceived “before” the stationary one was determined individually. Cumulative Gaussian functions were fitted to these data according to the MLE method. The mean of the function then estimated the position of the moving object perceived as equal to the stationary object, and the dispersion parameter estimated judgment accuracy.

Experiment 2: Short stimulus and both objects were always haptic. Intensity (1.5 vs. 3.0 N) and duration of the short stimulus were varied within participants; the short stimulus could be given during the 2nd, 3rd, 4th, or 5th partial movement. Each combination of experimental condition, position of the short stimulus, starting position of the movement, partial movement, and finger moved (left vs. right) was presented once per session, for a total of 2 sessions of 3.5 hours each. Which finger was moved changed every 56 runs; otherwise, the order of runs was completely randomized.

Data Collection Method:

Data collection in the presence of an experimenter

• Computer-Supported

Population:

Psychology students; young adults

Survey Time Period:

Experiment 1: 2 sessions of 2.5 h each within one week
Experiment 2: 2 sessions of 3.5 h each within one week

Sample:

Convenience sample

Gender Distribution:

76 % female subjects
24 % male subjects

Age Distribution: 20-27 years

Spatial Coverage (Country/Region/City): Germany/Hessen/Gießen

Subject Recruitment:

Recruitment via mailing list for Psychology students at the Giessen University

Sample Size:

Experiment 1: 8 individuals; Experiment 2: 9 (+2) individuals

Return/Drop Out:

Experiment 2: Data from 2 subjects (above: +2) were removed in the final analysis because judgment accuracy in at least one of the 4 conditions was judged to be an upward outlier (JND was 2.5 standard deviations above sample average; outlier participants were successively determined.