Temporal difference thresholds and repetitive stimulation: Can click trains improve temporal sensitivity?

Trains of auditory clicks increase subsequent judgements of stimulus duration by approximately 10%. Scalar timing theory suggests this is due to a 10% increase in pacemaker rate, a main component of the internal clock. The effect has been demonstrated in many timing tasks, including verbal estimation, temporal generalisation, and temporal bisection. However, the effect of click trains has yet to be examined on temporal sensitivity, commonly measured by temporal difference thresholds. We sought to investigate this both experimentally; where we found no significant increase in temporal sensitivity, and computationally; by modelling the temporal difference threshold task according to scalar timing theory. Our experimental null result presented three possibilities which we investigated by simulating a 10% increase in pacemaker rate in a newly-created scalar timing theory model of thresholds. We found that a 10% increase in pacemaker rate led to a significant improvement in temporal sensitivity in only 8.66% of 10,000 simulations. When a 74% increase in pacemaker rate was modelled to simulate the filled-duration illusion, temporal sensitivity was significantly improved in 55.36% of simulations. Therefore, scalar timing theory does predict improved temporal sensitivity for a faster pacemaker, but the effect of click trains (a supposed 10% increase) appears to be too small to be reliably found in the temporal difference threshold task.

Elucidation of a lingual detection mechanism for high-viscosity solutions in humans

While perception of high-viscosity solutions (η>1000cP) is speculated to be linked to filiform papillae deformation, this has not been demonstrated psychophysically. Presently, just-noticeable-viscosity-difference thresholds were determined using the forced-choice staircase...

Investigation of Spatial Chromatic Contrast around 5 Colour Centres

The goal of this research work is to generate high quality chromatic contrast sensitivity (CCS) data over a large range, especially at low spatial frequencies surrounding 5 colour centres, e.g.white, red, yellow, green and blue. An experiment was carried out using forced-choice stair-case method to investigate the visible colour difference thresholds in different colour changing directions at different spatial frequencies. The just noticeable difference (JND) ellipses at different spatial frequencies were used to represent the data.

Difference Thresholds for the Perception of Sinusoidal Vertical Stimuli of Whole-Body Vibrations in Ranges of Amplitude and Frequency Relevant to Ride Comfort

Minor differences in the vibration characteristics of a vehicle may greatly influence the comfort experienced by the driver. Therefore, such characteristics are significant in the process of vehicle development. In this experimental study, just-noticeable differences were determined for sinusoidal vertical whole-body vibrations at the frequencies 1.3 Hz and 6.0 Hz, and for the vibration amplitudes 0.2 m/s², 0.5 m/s² and 1.2 m/s². The stimulation set up was realised using a test rig constituting a seating position similar to that in a real vehicle environment. A transformed one-up-three-down method, in conjunction with a two-interval forced choice procedure, was used to determine difference thresholds, in accordance with Weber’s Law, for 14 test subjects. Median relative difference thresholds in the range of 6.7% to 11.0% were observed, and were examined for statistical significance (α < 0.05) and practical importance on amplitude and frequency, with respect to this law. The results showed a frequency-dependence at the lowest vibration amplitude and an amplitude-dependence for both frequencies from a statistical point of view. However, the amplitude-dependence at 6.0 Hz was considered as negligible for practical use.