When an object is more than a binding of its features: Evidence for two mechanisms of visual feature integration

People spontaneously integrate the features of visual events into episodic structures that are reactivated if their ingredients match aspects of the current input. Feature integration has been attributed to either the detection of feature conjunctions or the ad hoc binding of feature codes (e.g., by neural synchronization). We report evidence suggesting that both kinds of integration mechanisms coexist. Replicating earlier findings, repeating one visual feature facilitated performance but only if other visual features were also repeated. However, this effect was more pronounced with real objects as compared to arbitrary combinations of shapes and colours. Moreover, the real-object effect was restricted to visual feature integration but did not extend to visuomotor integration, suggesting that the underlying mechanism subserves perception only. We suggest a dual-process feature-integration model that distinguishes between ad hoc binding, which operates on any possible combination of features alike, and conjunction detection, which selectively operates on familiar feature combinations.