Visual pop-out in barn owls: Human-like behavior in the avian brain

Abstract

Visual pop-out is a phenomenon by which the latency to detect a target in a scene is independent of the number of other elements, the distractors. Pop-out is an effective visual-search guidance that occurs typically when the target is distinct in one feature from the distractors, thus facilitating fast detection of predators or prey. However, apart from studies on primates, pop-out has been examined in few species and demonstrated thus far in rats, archer fish, and pigeons only. To fill this gap, here we study pop-out in barn owls. These birds are a unique model system for such exploration because their lack of eye movements dictates visual behavior dominated by head movements. Head saccades and interspersed fixation periods can therefore be tracked and analyzed with a head-mounted wireless microcamera-the OwlCam. Using this methodology we confronted two owls with scenes containing search arrays of one target among varying numbers (15-63) of similar looking distractors. We tested targets distinct either by orientation (Experiment 1) or luminance contrast (Experiment 2). Search time and the number of saccades until the target was fixated remained largely independent of the number of distractors in both experiments. This suggests that barn owls can exhibit pop-out during visual search, thus expanding the group of species and brain structures that can cope with this fundamental visual behavior. The utility of our automatic analysis method is further discussed for other species and scientific questions.

Attention-like processes in insects

“…They thus seem to be searching for targets serially. This is a marked difference from the parallel visual search mechanisms we see in humans and other vertebrates where target detection is independent of the number of distractors [39][40][41]. test selective attention of free-flying bumblebees to colour and shape during simultaneous tasks (after [34]).…”

Visual search in barn owls: Task difficulty and saccadic behavior

“…In recent years, knowledge about visual search and its underlying neural mechanisms has extended from primates (Balan, Oristaglio, Schneider, & Gottlieb, 2008;Bichot & Schall, 1999;Chelazzi, Miller, Duncan, & Desimone, 1993;Ipata, Gee, Gottlieb, Bisley, & Goldberg, 2006) to nonprimate species. For instance, visual search has been studied in rats (Botly & De Rosa, 2012), pigeons (Blough, 1979), archerfish (Ben-Tov, Donchin, Ben-Shahar, & Segev, 2015;Rischawy & Schuster, 2013), and barn owls (Harmening, Orlowski, Ben-Shahar, & Wagner, 2011;Ohayon, Harmening, Wagner, & Rivlin, 2008;Orlowski et al, 2015). In our experiments with barn owls, employing a paradigm of overt attention, we have already shown that barn owls are attracted to salient locations as assessed with a bottom-up computational model (Itti & Koch, 2001;Ohayon et al, 2008).…”

“…In a free-viewing task with elongated items, one of which (the target) was differently oriented from the others (the distracters), naïve barn owls fixated the target faster, longer, and more often than a randomly chosen distracter (Harmening et al, 2011). When barn owls were explicitly trained to search for the target, we could demonstrate a pop-out effect-that is, their search time was largely independent of set size in two feature searches for luminance contrast and for orientation (Orlowski et al, 2015).…”

“…The experimental procedures and the basic setup were mostly unchanged from Orlowski et al (2015). Briefly: We tracked overt attention of barn owls by recording first-person-view videos via the headmounted OwlCam in three different experiments.…”

“…The videos were analyzed with a custom-written semiautomated MATLAB program described in detail by Orlowski et al (2015). Briefly, each video was segregated into fixations and saccades.…”