┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ 装 ┊ ┊ ┊ ┊ ┊ 订 ┊ ┊ ┊ ┊ ┊ 线 ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊ ┊

force references or over the three angle references (p > 0.4, Friedman tes law can be upheld for the Relativeforce arange)differenud angle thresholds for steady state(medians and interquardleMedian difference

Driver pereepfiun of.waring feel produce. The bias causes magnitude production to yield steeper slopes (i.e. higher values for n) than magnitude estimation.

The third experiment employed both magnitude estimation and magnitude production to develop a force

The mean relative difference thresholds across the magnitudes of the reference stimuli were 15 percent when detecting changes in force and 14 per cent when detecting changes in angle. This suggests no fundamental difference in the accuracy of detecting changes in force and angle, implying that force and angle provide equally discriminable changes in feedback.

For the perception of force, the 15 per cent relative difference threshold was obtained with a correct performance level of 79.4 per cent. Direct comparison with the aforementioned studies of the perception of force are not possible, as correct response levels are not presented in those studies. For the perception of angle, 14 per cent in the present study compares the a difference threshold for limb movement in the range 10-18 per cent (for a 71 per cent correct performance level) according to Rinker et al. [18], and 8 per cent (for a 71 per cent correct performance level) according to Jones of perception of steady state steering-wheel and steady state steering-wheel angle. 3.3 Rate of growth of sensation

The rate of growth of sensation of stimuli has often been determined using Stevens' power law Where is the sensation magnitude,is the stimulus intensity, k is a scalar constant depending on the conditions, and n is the value of the exponent that describes the rate of growth of sensation of the stimulus and depends on the sensory modality (e.g perception of force, or perception of loudness).

Previous studies have reported rates of growth of sensation of force and weight with exponents between。and 2.0 over a variety of experimental conditions 121-2引A study of the haptic sensation of finger span Steven. and Stone using widths of 2.3-63.7 mm reported an exponent of 1.33 using magnitude estimation.

The value of the exponent n may be determined by either magnitude estimation or magnitude production. Magnitude estimation requires subjects to make numerical estimations of the perceived magnitudes of sensations, whereas magnitude production requires subjects to adjust the stimulus to produce sensory magnitudes equivalent to given numbers These methods have systematic biases which Stevens called a 'regression effect. The biasese attributed to a tendency for subjects to limit the range of stimuli over which they have control; so with magnitude estimation they limit the range of numbers that they report, and in magnitude production they limit the range of stimuli that they For magnitude