Among others, these findings led Titchener (1908) to formulate the law of prior entry: "the object of attention comes to consciousness more quickly than the objects which we are not attending." As we shall see, these two kinds of accounts--differential latencies and attention--are nowadays still offered as explanations of the outcomes of related psychophysical tasks used to assess the spatiotemporal features of sensory perception, such as the flash-lag effect (FLE) and temporal order judgments (TOJ).
In the midst of a variety of other visual illusions arising from the same question, the flash-lag effect (FLE) stands out as a still intriguing perceptual phenomenon, hotly debated over the last 12 years (Baldo & Klein, 1995; Eagleman, 2001; Eagleman & Sejnowski, 2000; Krekelberg & Lappe, 2001; Lappe & Krekelberg, 1998; Nijhawan, 1994, 2002; Nijhawan & Khurana, 2000; Purushothaman, Patel, Bedell, & Ogmen, 1998; Schlag & Schlag-Rey, 2002; Whitney, 2002).
Nijhawan originally interpreted the flash-lag effect as resulting from a spatial extrapolation of the moving object ("motion extrapolation"), owing to the predictability of its trajectory.
Our first demonstration of a putative role of visual attention in forging the flash-lag effect was based on a rather hazy empirical foundation (Baldo & Klein, 1995).
Representational momentum and related types of displacement reflect properties of the world and properties of mental representation, and so a consideration of representational momentum and related types of displacement contribute an important component of contemporary psychophysics, and also broaden the reach of psychophysics to include numerous topics not usually considered within psychophysics (e.g., naive physics, boundary extension, flash-lag effect, aesthetics, mental imagery).
Flash-lag effect. When a stationary stimulus is briefly flashed at a position that is aligned with a continuously visible moving target, the position of the flashed stimulus seems to lag behind the position of the moving target, and this is referred to as the flash-lag effect (for review, see Krekelberg & Lappe, 2001; Nijhawan, 2002).
Displacement could potentially contribute to a wide range of additional perceptual and cognitive phenomena, and these include other specific biases in spatial processing (e.g., flash-lag effect, motion capture) and more general issues in cognition (e.g., naive physics, causal cognition).