Dividing attention between color and shape: Evidence of coactivation

Abstract

When attention is divided between spatially distinct objects, the time to detect a target decreases when two or more targets are present. This redundancy gain can be accounted for by an interactive race model (Mordkoff & Yantis, 1991) in which separate decisions are made about each object, but environmental contingencies among the objects can influence decision times. In the present study, we examined whether the model also accounts for performance when attention must be divided between stimulus attributes other than spatial location. Subjects made targetpresent responses when displays included a prespecified color, a prespecified letter, or both target features. The data violated the predictions of all separate-activations models, including the interactive race model. Two control experiments ruled out an alternative account based on task complexity. We conclude that coactivation occurs when target attributes from two separable dimensions are simultaneously present, but not when target attributes come from the same dimension. A modular hybrid of race and coactivation models is tentatively proposed.

The detection of feature singletons defined in two dimensions is based on salience summation, rather than on serial exhaustive or interactive race architectures

“…contained a prespecified color, a prespecified letter, or both target-defining features. Even though there were no contingencies in the experimental design favoring redundant-over single-signal trials, Mordkoff and Yantis (1993) found significant violations of the RMI, indicating that color and form were processed coactively rather than according to an independent-or an interactive race model. However, this finding does not extend to the question of saliency summation in visual search, for several reasons: First, Mordkoff and Yantis's (1993) paradigm did not involve any search component, since there was no uncertainty about the target location; second, correct responses required the identification of object featuresin contrast with the detection of feature singletons as was required in the present study, in which responses could be based solely on the "featureless" activation of units in the salience map.…”

“…The same arguments apply to a study by Feintuch and Cohen (2002), in which observers also had to perform an object identification task, with targets defined by a certain color, a certain form, or both. Both the Mordkoff and Yantis (1993) and the Feintuch and Cohen studies indicated that there are postselective processes whose outputs are integrated in a coactive fashion. Indeed, it is likely that coactive processing architectures are implemented from early sensory through postselective to motor stages of processing (see, e.g., Miller, 2007).…”

“…However, this finding does not extend to the question of saliency summation in visual search, for several reasons: First, Mordkoff and Yantis's (1993) paradigm did not involve any search component, since there was no uncertainty about the target location; second, correct responses required the identification of object featuresin contrast with the detection of feature singletons as was required in the present study, in which responses could be based solely on the "featureless" activation of units in the salience map. Thus, Mordkoff and Yantis (1993) were interested in redundancy gains in object identification rather than in the summation of feature contrast into a salience map. The same arguments apply to a study by Feintuch and Cohen (2002), in which observers also had to perform an object identification task, with targets defined by a certain color, a certain form, or both.…”

Functional asymmetry and interhemispheric cooperation in the perception of emotions from facial expressions

“…In normal viewers the RTE has also been demonstrated with meaningful stimuli such as words (Hasbrooke and Chiarello 1998;Mohr et al 1996), numbers (Ratinckx and Brysbaert 2002), drawings of animals or objects (Koivisto 2000), and familiar neutral faces (Mohr et al 2002). Likewise, direct tests have often shown violations or race models, thereby providing support for models based on neural coactivation and interhemispheric summation (Corballis 2002;Grice and Reed 1992;Iacoboni et al 2000;Iacoboni and Zaidel 2003;Marzi et al 1996;Miller 1982Miller , 1986Miniussi et al 1998;Mordkoff and Yantis 1993;Reuter-Lorenz et al 1994;Savazzi and Marzi 2002).…”

“…For instance, the RTE has been shown using simple flashes (Corballis 2002;Savazzi and Marzi 2002), checkerboards (Miniussi et al 1998), shapes and colours (Mordkoff and Yantis 1993), letters (Grice and Reed 1992;Mordkoff and Miller 1993), and letterstrings (Marks and Hellige 1999), on healthy subjects as well as on neurological patients (with hemianopia and blindsight: de Gelder et al 2001;Marzi et al 1986;hemispherectomy: Tomaiuolo et al 1997;split-brain: Corballis 1995;Forster and Corballis 2000;Iacoboni et al 2000;Mohr et al 1994;Reuter-Lorenz et al 1994;Corballis 2002, 2003;and visual extinction: Marzi et al 1996). In normal viewers the RTE has also been demonstrated with meaningful stimuli such as words (Hasbrooke and Chiarello 1998;Mohr et al 1996), numbers (Ratinckx and Brysbaert 2002), drawings of animals or objects (Koivisto 2000), and familiar neutral faces (Mohr et al 2002).…”