Saccadic Momentum and Facilitation of Return Saccades Contribute to an Optimal Foraging Strategy

Abstract

The interest in saccadic IOR is funneled by the hypothesis that it serves a clear functional purpose in the selection of fixation points: the facilitation of foraging. In this study, we arrive at a different interpretation of saccadic IOR. First, we find that return saccades are performed much more often than expected from the statistical properties of saccades and saccade pairs. Second, we find that fixation durations before a saccade are modulated by the relative angle of the saccade, but return saccades show no sign of an additional temporal inhibition. Thus, we do not find temporal saccadic inhibition of return. Interestingly, we find that return locations are more salient, according to empirically measured saliency (locations that are fixated by many observers) as well as stimulus dependent saliency (defined by image features), than regular fixation locations. These results and the finding that return saccades increase the match of individual trajectories with a grand total priority map evidences the return saccades being part of a fixation selection strategy that trades off exploration and exploitation.

Temporal oculomotor inhibition of return and spatial facilitation of return in a visual encoding task

“…In the literature on visual scenes, some researchers claim to have observed a decreased probability of returning to a previously fixated location (Klein and MacInnes, 1999), while others have observed facilitation of return, in that eye movements to previous locations are more likely than many other eye movements (Hooge et al, 2005; Smith and Henderson, 2009, 2011a, b; Wilming et al, 2013). Likewise, in reading the evidence is mixed.…”

Modelling Task-Dependent Eye Guidance to Objects in Pictures

“…One such example is the IOR. Depending on the task, different variants of IOR exist [113]. In our model, the priority map explicitly uses IOR in a classic way, by suppressing the response at the currently attended location.…”

“…However, a reduction or an enhancement in the reward likelihood can modulate the IOR at the priority map level. In general, this multiple level interaction can be a way of framing the discussion surrounding a functional interpretation of IOR (that is fostering or not optimal foraging behaviour, see [113]). …”

“…Note that, in the absence of object information, P (F(t)|O) = P (F(t)) and L(t) boils down to a classic salience map. The attentional priority is related to both the object's salience and any top-down biases that influence the relative importance of that object to the subject, including the suppression of objects that have already been examined during visual search, thus playing a role in participating to the elusive Inhibition of Return (IOR) mechanism [113]. The reduction in the response to a stimulus that has been fixated essentially acts as a form of short term memory that lets the priority map keep track of which potential targets have been examined.…”

Modeling peripheral visual acuity enables discovery of gaze strategies at multiple time scales during natural scene search

“…Journal target location (Ehinger, Hidalgo-Sotelo, & Torralba, 2009); factors that are ecologically relevant but not specific to the task, such as intrinsic value (Gottlieb, 2012); and exploratory strategies for minimizing uncertainty (Gottlieb, Oudeyer, Lopes, & Baranes, 2013;Renninger, Verghese, & Coughlan, 2007). In addition, change in direction between successive saccades (Wilming, Harst, Schmidt, & König, 2013) and natural statistics of saccade magnitude and direction (Tatler & Vincent, 2009) also enable saccade prediction. Predictive models of eye movements are derived from priority maps comprising one or more of the above factors.…”