Grouping is suggested as a two-phase process: base grouping and incremental grouping (Roelfsema,
2006). Base groupings are coded by single neurons tuned to multiple features and are computed rapidly because they reflect the selectivity of feed-forward connections. A second phase, incremental grouping, enhances the responses of neurons' coding features, but it takes more time than does base grouping because it also relies on horizontal and feedback connections. This view is consistent with our previous data (Polat & Sagi,
2006; Sterkin & Polat,
2008) suggesting that the process of grouping consists of two phases: The first one is suppressive, fast, and transient and the second one is facilitative, delayed, slower, and sustained. According to this view, the first phase of grouping, which is dominated by I, acts to reduce the activity in the network (suppression). Then the second phase of grouping, dominated by lateral E, provides segregation of contours from the background and makes them salient for further processing (Polat & Sagi,
2006; Sterkin & Polat,
2008). Indeed, physiological studies show that the latter phase provides a segregation of figures from the ground (Lamme,
1995; Roelfsema,
2006; Roelfsema, Tolboom, & Khayat,
2007). Thus, crowding may be related to the first phase of grouping and may be considered as the suppressive phase. We showed here and recently (Lev, Yehezkel, et al.,
2014) that the suppressive effect (crowding) is transient but that longer presentation times enable correct identification of the target. Thus, this second part can be viewed as the second phase of grouping, which enables figure–ground segregation (Neri & Levi,
2007; Polat & Sagi,
2006; Sterkin & Polat,
2008) and, hence, correct identification of the target from the background of flankers (uncrowding). We sought a correlation between crowding and masking and found the maximal correlation for conditions where E/I reaches an optimal level between lateral E and local I (e.g., at 3
λ and 60 and 120 ms; see
Figure 9). This most likely indicates the transition point from the first phase (inhibitory) to the second phase (excitatory).