A violation of Fitts' Law occurs when a target range is presented before and during movement

Exp Brain Res. 2023 Oct;241(10):2451-2461. doi: 10.1007/s00221-023-06687-6. Epub 2023 Aug 31.

Abstract

According to Fitts' Law, the time to reach a target (movement time, MT) increases with distance. A violation of Fitts' Law occurs when target positions are outlined before and during movement, as MTs are not different when reaching to the farthest and penultimate targets. One hypothesis posits that performers cognitively process the edges of a target array before the center, allowing for corrective movements to be completed more quickly when moving to edge targets compared to middle targets. The objective of this study was to test this hypothesis by displaying a target range rather than outlines of individual targets in an effort to identify the effects of array edges. Using a touch-screen laptop, participants (N = 24) were asked to reach to one of three targets which would appear within a presented range. Separately, targets were also presented without a range to determine if the display protocol could evoke Fitts' Law. Movements were assessed with the touch screen and optical position measurement. A main effect was found for relative position within a range (touch: F2,44 = 15.4, p < 0.001, η2p = 0.412; position: F2,40 = 15.6, p < 0.001, η2p = 0.439). As hypothesised, MT to the farthest target in a range was not significantly different than MT to the middle target (touch: p = 0.638, position: p = 0.449). No violation was found when a target range was not presented (touch: p = 0.003, position: p = 0.001). Thus, a target range reproduces the Fitts' Law violation previously documented with individually outlined targets, which supports and extends the discussed hypothesis.

Keywords: Cognition; Fitts’s law; Kinematic analysis; Manual aiming; Reaching.

MeSH terms

  • Acrylic Resins*
  • Dioctyl Sulfosuccinic Acid*
  • Humans
  • Movement
  • Phenolphthalein
  • Puromycin

Substances

  • Coe Comfort
  • Acrylic Resins
  • Dioctyl Sulfosuccinic Acid
  • Phenolphthalein
  • Puromycin