Academic journal article Attention, Perception and Psychophysics

Prioritization of Looming and Receding Objects: Equal Slopes, Different Intercepts

Academic journal article Attention, Perception and Psychophysics

Prioritization of Looming and Receding Objects: Equal Slopes, Different Intercepts

Article excerpt

Franconeri and Simons (2003) reported that simulated looming objects (marked by a size increase) captured attention, whereas simulated receding objects (marked by a size decrease) did not. This finding has been challenged with the demonstration that receding objects can capture attention when they move in three-dimensional depth. In the present study, we compared the effects of objects that either loomed or receded in depth. The results of two experiments showed that whereas both motion types benefited from attentional prioritization, as judged by their search slopes, looming objects elicited shorter response times (RTs). We conclude that both motion types attract attention during search; however, the RT advantage for looming motion seems to reflect a processing enhancement that occurs outside of selection and is conferred on the basis of motion direction.

Attention is often said to be the ability to select certain aspects of the environment in preference to others. Since we are unable to attend to all stimulus information at once, we select only what is likely to be behaviorally important. Although the selection of these stimuli is largely determined by a person's intentions and goals (see, e.g., Folk, Remington, & Johnston, 1992; Folk, Remington, & Wright, 1994), it has long been argued that certain stimulus features, such as the abrupt onset of a stimulus object, have the potential to summon attention automatically (e.g., Yantis & Jonides, 1984). More recently, there has been considerable debate regarding the types of motion information that might also attract attention automatically. In a series of exchanges, Franconeri and Simons (2003, 2005) and Abrams and Christ (2003, 2005a, 2005b, 2006) have emphasized the relative importance, respectively, of motion per se and of motion onset. That is, is attention as likely to be attracted to a moving object during the object's motion as it is to be attracted upon commencement of the motion? Further embedded in this debate is the question of whether motion direction can be influential in the marshalling of attention. That is, does looming motion summon attention more effectively than does receding motion? This question is the focus of interest in the present study.

The notion that the human visual system might be preferentially sensitive to looming motion is persuasive. Studies of animal neurophysiology have revealed neurons in the visual cortex of rhesus monkeys that selectively respond to stimuli that simulate motion toward or away from the animal (Zeki, 1974a, 1974b). Moreover, single-cell recordings in the medial superior temporal area of the macaque monkey have also revealed cells that are sensitive to motion direction, many more of which respond to looming than to receding motion (Tanaka & Saito, 1989). These findings concur with those from animal behavior studies that have shown that the rapid expansion (i.e., looming) of circular shadows elicits fear responses in adult and infant rhesus monkeys, whereas rapidly contracting (receding) shadows do not (Schiff, Caviness, & Gibson, 1962). Human infants, too, show sensitivity to looming motion. Schmuckler, Collimore, and Dannemiller (2007) recently compared the blink responses of 4- to 5-month-old infants who perceived objects looming on collision or near-miss trajectories. The results showed that objects on a collision course elicited a greater number of blink responses than did those on noncollision trajectories, suggesting that infants are able to discriminate subtle differences in motion direction. Additionally, Jouen (1990; see also Jouen, Lepecq, Gapenne, & Bertenthal, 2000) showed that even 3-day-old neonates responded to looming flow motion patterns by tilting their heads backward. Interestingly, the extent to which the neonates tilted their heads correlated positively with the optic flow velocity of the looming stimuli. Taken together, these results, in light of the perceptual inexperience of the infants tested, suggest that sensitivity to looming motion might be hardwired. …

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