A new object captures attention--but only when you know it's new

Do sudden onsets need to be perceived as new objects to capture attention? The interplay between sensory transients and display configuration

Yantis and Jonides (1984) and Jonides and Yantis (1988) reported robust involuntary attentional capture by sudden-onsets, the origin of which has been debated. Prominent accounts have highlighted aspects that include the "new object" status of a sudden-onset (Yantis & Hillstrom, 1994) and the substantial luminance changes accompanying their appearance (Gellatly, Cole & Blurton, 1999; Franconeri, Hollingworth & Simons, 2005), including relative differences in the amount of sensory change between target and nontarget items (Pinto, Olivers & Theeuwes, 2008). In this research we dissociate the amount of sensory change accompanying sudden onsets from the extent to which they appear as newly created objects in search displays. We attempted to determine the relative contribution of local sensory changes and display configuration to attentional capture by sudden-onsets. We showed that the display configuration of old objects modulates the impact of capture caused by sudden-onsets.

A new object captures attention--but only when you know which objects are old

According to the new object hypothesis (see, e.g., Yantis & Hillstrom, Journal of Experimental Psychology: Human Perception & Performance, 20, 95-107, 1994), an object appearing as a sudden onset captures attention because its appearance demands an immediate updating of visual short-term memory. This hypothesis was tested in three experiments using a procedure that allowed an object to be added to the display but, crucially, without incurring onset transients (Franconeri, Hollingworth, & Simons, Psychological Science, 16, 275-281, 2005). The latter showed that an object inserted in this fashion failed to capture attention. As a test of the new object hypothesis, this procedure assumes that the observers had encoded the display before the new object was introduced. If this assumption is not fulfilled, the new and the old objects cannot be distinguished one from the other. It was, however, unclear whether the encoding had taken place in the Franconeri et al. experiments. We showed that when circumstances were congenial to the encoding of the display before an additional object interposed, then the object successfully captured attention. But when the encoding of the initial display was either difficult or impossible, the additional object failed to capture attention.

New objects do not capture attention without a sensory transient

Attention capture occurs when a stimulus event involuntarily recruits attention. The abrupt appearance of a new object is perhaps the most well-studied attention-capturing event, yet there is debate over the root cause of this capture. Does a new object capture attention because it involves the creation of a new object representation or because its appearance creates a characteristic luminance transient? The present study sought to resolve this question by introducing a new object into a search display, either with or without a unique luminance transient. Contrary to the results of a recent study (Davoli, Suszko, & Abrams, 2007), when the new object's transient was masked by a brief interstimulus interval introduced between the placeholder and search arrays, a new object did not capture attention. Moreover, when a new object's transient was masked, participants could not locate a new object efficiently even when that was their explicit goal. Together, these data suggest that luminance transient signals are necessary for attention capture by new objects.