Hastening Orientation Sensitivity

1. Hastening Orientation Sensitivity Kristen Strong, Kei Kurosawa& Nestor Matthews Department of Psychology, Denison University, Granville OH 43023 USA Results Motivation Discussion Figure 1- Pre-training thresholds were computed from the psychometric functions shown in Figure 1. The monotonic trends indicate that any limitations that may have existed were sensory, not conceptual. T-tests revealed that the two groups were comparable at each axis and that each group demonstrated a significant oblique effect. Figure 2- At each axis, threshold duration decreased significantly with practice. These improvements differ from those of previous studies,1,2 which found improvements at the oblique axis only. Figure 3- In addition to the hastening shown in Figure 2, significant sharpening is shown in Figure 3. This sharpening, too, occurred at each axis, unlike that of previous studies1,2 in which sharpening occurred at the oblique axis only. Figure 4- The data in Figure 4 indicate that the practice based improvements at the trained axes did not generalize to the untrained axes. This specificity argues against a general-learning account of the improvements. Instead, the data suggest that the improvements were sensory. Previous studies1,2 showed that the ability to see subtle angular differences can improve with practice at horizontal but not diagonal axes. However, by using a different methodological approach to study perceptual learning along each axis, we sought to show otherwise. Specifically, we wondered if orientation sensitivity could be both hastened and sharpened by training on relatively wide angles at multiple stimulus durations. Figure 1 Figure 2 Method Pre/ Post Training- The stimuli were sequentially presented gratings that were preceded and followed by a bulls-eye mask (see figure below). Participants judged whether the second grating in each pair was clockwise or anti-clockwise to the first. The stimulus duration across all 1,000 trials was 200 msec, and the angular difference ranged from -12 to 12 degrees. Cardinal-axis (horizontal) trials were blocked separately from oblique-axis (diagonal) trails. At each axis, 84% angular difference-thresholds were computed for each participant. Participants were then split into two statistically indistinguishable groups for training. Training- During training each participant trained on only one axis. Stimuli were presented at varying durations (8-158 msec) and participants trained on twice their calculated 84% threshold. There were 10 blocks of 70 trials in each daily session. Each participant completed 5 days of training. Figure 3 Figure 4 The Bottom Line Our data suggest that the visual system’s response to subtle angular differences can be both hastened and sharpened, at cardinal and oblique axes. References Vogels & Orban (1985) PMID 3832592. Matthews & Welch (1997) PMID 9038408. This poster can be viewed and downloaded at http://www.denison.edu/~matthewsn/hastening05.html