How does the motion–position interaction in the FDE in random motion occur? In other words, what mechanism is responsible for the broad temporal tuning of the FDE induced by preattentive motion information? The pattern of the temporal tuning similar to those we found has often been observed and discussed in the previous FDE literature (Durant & Johnston,
2004; Shim & Cavanagh,
2005). As mentioned above, Shim and Cavanagh (
2005) found a much broader temporal tuning than those we found, but there are also similarities in that both temporal tunings had an asymmetric pattern and a bias in the past direction. In their study, Shim and Cavanagh attributed this pattern of the temporal tuning to a directionally modulated attentional repulsion effect. Because subjects attentively tracked the pattern of the rotating disk in their study, this covert movement of the attentional focus might cause the mislocalization of the flash more often when presented ahead of the tracking target than behind, as in the case of the mislocalization effect seen with actual eye movements (Matsumiya & Uchikawa,
2000). However, this cannot be the case in our study because we used a random motion sequence, in which attentional tracking is impossible. Durant and Johnston (
2004) used a rotating bar as an inducer of the FDE and obtained a temporal tuning that is very similar to our results. They proposed that feedback signals from extrastriate areas like MT/V5 to area V1 is necessary for the FDE to occur and argued that the temporal tuning reflects the peak latency of the V1 cell responses. These authors argued that when feedback signals from MT/V5 arrive at the right time around the peak latency of the V1 cell responses, the maximal FDE occurs. This is surely a possibility, but a more parsimonious idea may be that the broad temporal tuning might reflect stochastic fluctuation of temporal binding between a jump and a flash. The lag and asymmetric form may reflect a time-consuming computational process that binds a flash to motion, which gets activated only after the flash is processed at a certain level in the visual system. This explanation shares common characteristics with the explanations of the flash-lag effect that have been proposed by several researchers. The flash-lag effect is a phenomenon in which a flash presented adjacent to a moving stimulus appears to lag behind it (MacKay,
1958; Mateeff & Hohnsbein,
1988; Nijhawan,
1994), and the main cause of this effect is thought to be that the perceived timing of the flash is delayed relative to the moving stimulus (Brenner & Smeets,
2000; Murakami,
2001a,
2001b; Whitney, Cavanagh, & Murakami,
2000; Whitney & Murakami,
1998; Whitney, Murakami, & Cavanagh,
2000). Several studies suggest that the flash-lag effect is caused by a sluggish computational process that binds the flash and the moving stimulus rather than by the simple differential latency between the flash and the moving stimulus (Arnold, Durant, & Johnston,
2003; Arnold, Ong, & Roseboom,
2009; Brenner & Smeets,
2000; Cai & Schlag,
2001; Fukiage & Murakami,
2010). It should be noted that the flash-lag effect is different from the FDE in that the task in the flash-lag effect requires an explicit comparison between the positions of the flash and the moving stimulus, and it might be that this explicit comparison more directly reflect the temporal property of the binding process. Nevertheless, the time constant we estimated in this study is similar to those of distributed differential latency obtained in the studies of the flash-lag effect that also used random motion as the inducer (Fukiage & Murakami,
2010; Murakami,
2001a,
2001b). Although Durant and Johnston found that the flash-lag effect was smaller than the delay measured with the FDE, using their stimuli, the smooth motion they used might activate more than one mechanism that can influence position judgments. Unpredictability of random motion might be best to extract the pure effect of a bottom-up mechanism mediating both the FDE and the flash-lag effect. Therefore, a common mechanism, which binds a stationary object with a moving one or allocates objects to a kind of spatiotemporal map, might be responsible for both the FDE and the flash-lag effect. This idea is largely speculative, but there is also another study that suggests the existence of a high-level binding mechanism with large temporal imprecision (Linares, Holcombe, & White,
2009).