ISSN:
1432-1106
Keywords:
Key words
;
Motion perception
;
Reaction time
;
Direction changeIntroduction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Recently Dzhafarov et al. presented a model explaining data on simple reaction time (RT) to unidimensional velocity changes. The authors suggested that having a motion with an initial velocity V 0, the velocity change detection system is reinitialized by means of a ”subtractive normalization” process. Therefore, any abrupt change from V 0 to V 1 is detected as if it were the onset of motion with a speed equal to |V 1–V 0|. They derived that the RT is a function of |V 1-V 0|–2/3. We tested this model for the case of two-dimensional velocity changes. Our subjects observed a random dot pattern that moved horizontally, then changed the direction of motion by an angle α in the range between 6° and 180° without changing the speed V. Speeds of 4 and 12 deg/s were used. The subjects reacted as quickly as possible to the direction change. The RTs asymptotically decreased with increasing α; with 12 deg/s speed the RTs were shorter than those obtained with 4 deg/s. It was shown that the data can be well described as a function of |V 1–V 0|–2/3=(2Vsin(α/2))–2/3. An extension of the ”subtractive normalization” hypothesis for the case of two-dimensional velocity changes is proposed. It is based on the assumption that the velocity vector V 1 after the change is decomposed into two orthogonal components. Alternative explanations based on the use of position or orientation cues are shown to contradict the data.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002210050636
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