The number line effect reflects top-down control

Abstract

Human attention is normally conceived as a limited capacity process that can be controlled in either an exogenous, reflexive manner or an endogenous, volitional manner (Broadbent, 1971;Posner, 1978). For several decades, the attention-cuing paradigm has provided a simple methodology for engaging and measuring these two forms of orienting (Posner, 1980;Posner, Snyder, & Davidson, 1980). Typically, reflexive attention has been triggered by a peripheral flash that does not predict where a visual target will appear. This attentional cue is followed by a target, demanding a manual detection response, appearing either at the cued location or at a noncued location. The usual result is that if the cue-target stimulus onset asynchrony (SOA) is less than 300 msec, reaction time (RT) is shorter when a target appears at a cued location versus a noncued location. Because attended items are processed more efficiently than nonattended items, the facilitation effect at the cued location is taken as evidence that the abrupt onset attracted attention to its location. And because the facilitation effect emerged rapidly in response to a cue that did not predict where the target would appear, the attention effect is considered to be reflexive in nature. For SOAs greater than 300 msec, RT becomes longer for targets appearing at the cued location than for those appearing at the noncued locations, reflecting the inhibition-of-return phenomenon. This inhibition effect at the cued location is taken as evidence that attention was withdrawn from the cued location and is inhibited in returning there (Posner & Cohen, 1984).The cuing methodology for volitional orienting is similar to the above, with two important exceptions. First, instead of an attentional cue being flashed in the periphery, a central directional cue, usually an arrow, points toward the cued location. Second, the arrow cue predicts where the target is most likely to appear. The usual result when this central predictive cuing methodology is used is that an RT advantage emerges relatively slowly at the cued location and then persists across the long cue-target SOAs, since there is little reason to shift attention away from where the target is most likely to appear (e.g., Jonides, 1981).Recently, a number of studies have shown that central directional cues do not need to be spatially predictive in Recent evidence indicates that central directional stimuli, such as eyes and arrows, trigger rapid, reflexive shifts of spatial attention. A study by Fischer, Castel, Dodd, and Pratt (2003) suggested that a similar effect might also apply to central numbers, as if a digit's meaning causes attention to be oriented to its relative position on a left-to-right mental number line. However, unlike central eyes and arrows, the orienting effect for central digits emerges slowly, suggesting that top-down endogenous processes may be mediating this effect. Here, we report a series of three experiments that strongly support this hypothesis. Experiment 1 replicated Fischer et al.'s left-to-right n...

Normal and Impaired Reflexive Orienting of Attention after Central Nonpredictive Cues

“…One first striking finding is that digits were ineffective in orienting attention when directly compared with eye gaze and arrows. The absence of cueing effect for digits seems to be at odds with the findings of Fischer et al (2003), but it is consistent with the results of recent studies on healthy participants (Casarotti, Michielin, Zorzi, & Umiltà, 2007;Galfano, Rusconi, & Umiltà, 2006;Ristic, Wright, & Kingstone, 2006). All these studies support the view that digits possess a low degree of automaticity in the hierarchy of cues that, although irrelevant for the task, can orient attention.…”

The temporary nature of number—space interactions.

“…For example, when asked to imagine numbers on a clock-face, number cues induces attentional shifts in accordance with the position of the number on the clock (Ristic, Wright, & Kingstone, 2006). Similarly, when providing the direct instruction to associate small numbers with right and large numbers with left, the number-based attentional cueing effect reverses as well (Galfano, Rusconi, & Umilta, 2006).…”

“…For example, while mapping small numbers to the beginning and large numbers to the end of the memorized sequence may be the default association, this can be easily changed by the instructions given to the participants (e.g. the request to imagine the numbers as hours on a clock-face, Ristic et al, 2006;or to associate small numbers with a right location and large numbers with a left one, Galfano, et al, 2006). Again, whereas the mental number line account has difficulties to explain these findings, the flexible nature of WM can easily account for these observations.…”

The role of the angular gyrus in the modulation of visuospatial attention by the mental number line

“…Interestingly, the mental number line does not only influence overt spatial responses but it also exerts an effect on the allocation of spatial attention prior to any explicit response (although it is still subject to debate whether this effect is automatic or susceptible of top-down control, cf. Galfano et al, 2006;Ristic et al, 2006). For instance, Fischer et al (2003) found that exposure to small numbers (1 or 2) preceding the presentation of the target stimulus in a simple visual detection task facilitated detection of target appearing in the left hemifield, while exposure to large numbers (8 or 9) facilitated target detection in the right hemifield (see also Stoianov et al, 2008).…”