We argue that mechanistic premises of “item-based” theories are not invalidated by the fixation-based approach. We use item-based theories to propose an account that does not advocate strict serial item processing and integrates fixations. The main focus of this account is feature integration within fixations. We also suggest that perceptual load determines the size of the fixations.

With a simple demonstration model, Hulleman & Olivers (H&O) effectively argue that theories of visual search need an overhaul. We point to related literature in which visual search is modeled in even more detail through the use of computational cognitive architectures that incorporate fundamental perceptual, cognitive, and motor mechanisms; the result of such work thus far bolsters their arguments considerably.

Hulleman & Olivers' (H&O's) proposal is a refreshing addition to the visual search literature. Although we like their proposal that fixations, not individual items should be considered a fundamental unit in visual search, we point out some unresolved problems that their account will have to solve. Additionally, we consider predictions that can be made from the account, in particular in relation to priming of visual search, finding that the account generates interesting testable predictions.

Hulleman & Olivers' (H&O's) model introduces variation of the functional visual field (FVF) for explaining visual search behavior. Our research shows how the FVF can be studied using gaze-contingent displays and how FVF variation can be implemented in models of gaze control. Contrary to H&O, we believe that fixation duration is an important factor when modeling visual search behavior.

Much of the evidence for theories in visual search (including Hulleman & Olivers' [H&O's]) comes from inferences made using changes in mean RT as a function of the number of items in a display. We have known for more than 40 years that these inferences are based on flawed reasoning and obscured by model mimicry. Here we describe a method that avoids these problems.

We highlight the importance of considering the variance produced during the parallel processing stage in vision and present a case for why it is useful to consider the “item” as a meaningful unit of study when investigating early visual processing in visual search tasks.

The Functional Visual Field (FVF) offers explanatory power. To us, it relates to existing literature on the flexibility of attentional focus in visual search and reading (Eriksen & St. James 1986; McConkie & Rayner 1975). The target article promotes reflection on existing findings. Here we consider the FVF as a mechanism in the Prevalence Effect (PE) in visual search.

We show that our item-based model, competitive guided search, accounts for the empirical patterns that Hulleman & Olivers (H&O) invoke against item-based models, and we highlight recently reported diagnostic data that challenge their approach. We advise against “forsaking the item” unless and until a full fixation-based model is shown to be superior to extant item-based models.

This commentary focuses on two related, open questions in Hulleman & Olivers' (H&O's) proposal: (1) the nature of the parallel attentive process that determines target presence within, and thus presumably the size of, the functional visual field, and (2) how the pre-attentive guidance mechanism must be conceived to also account for search performance in tasks that afford no reliable target-based guidance.

Using fixations as the fundamental unit of visual search is an appealing gear change in a paradigm that has long dominated attention research. To truly inform theories of search, however, additional challenges must be faced, including (1) an empirically motivated definition of fixation in the presence of fixational saccades and (2) the biases and limitations of transsaccadic perception and memory.

Finding relevant objects through vision, or visual search, is a crucial function that has received considerable attention in the literature. After decades of research, data suggest that visual fixations are more crucial to understanding how visual search works than are the attributes of stimuli. This idea receives further support from the field of haptic search.

We provide a mathematical category theory account of the size and location of the authors' Functional View Field (FVF). Category theory explains systematic cognitive ability via universal construction, that is, a necessary and sufficient condition for composition of cognitive processes. Similarly, FVF size and location is derived from a (universal) construction called a fibre (pullback) bundle.

Evidence from continuous search suggests that targets are detected by default, whereas distractors are processed in considerable depth. These observations shed light on task implementation and top-down control. Task implementation builds on forming dynamic distractor models, based on continuous integration of distractor-related information. Top-down control builds on using these models for testing upcoming stimulus information.

Hulleman & Olivers (H&O) identify a number of problems with item-based thinking and its impact on our understanding of visual search. I detail ways in which item-thought is worse than the authors suggest. I concur with the broad strokes of the theory they set out, and also clarify the relationship between their view and our recent theory of visual search.

Hulleman & Olivers' (H&O's) conceptual framework does not consider variation of fixation duration and its interaction with the size of the functional viewing field (FVF). Here we provide empirical evidence of a dynamic interaction between the two parameters, suggesting that fixations, as the central unit in H&O's framework, should be studied on both the spatial and temporal dimensions.

We argue that although the framework put forward by Hulleman & Olivers (H&O) can successfully explain much of visual search behaviour, it appears limited to tasks without precise target identification demands. In particular, we contend that the unit of selection may be larger than a single item in standard detection tasks, whereas the unit may mandatorily be item-based in compound tasks.

Hulleman & Olivers (H&O) argue that the primary unit in search should be fixations, and in doing so posit a Functional View Field (FVF). There is evidence from the object-based visual attention literature that the FVF may not process visual information uniformly. Here I sketch how object-based attention may influence processing within the FVF as well as the shape of the FVF.

A unified account of visual search in complex everyday environments requires additional deliberations on the functional grounding of Hulleman & Olivers' (H&O's) functional viewing field (FVF) model. Their model can accommodate exploitation of information that is distributed across the immediate environment. Yet the differences in search between genuinely interacting in the environment and merely watching it should challenge researchers to look further.

Even though we lack a precise definition of “item,” it is clear that people do parse their visual environment into objects (the real-world equivalent of items). We will review evidence that items are essential in visual search, and argue that computer vision – especially deep learning – may offer a solution for the lack of a solid definition of “item.”

I propose that there remains a central role for the item (or its equivalent) in a wider range of search and search-related tasks/functions than might be conveyed by the article. I consider the functional relationship between the framework and some aspects of previous theories, and suggest some challenges that the new framework might encounter.