The primary function of visual search is to gather information for guiding actions with persons, objects, and events in everyday environments. For example, a pedestrian walking down a busy city street, and a police officer chasing a suspect are examples of complex everyday environments that require people to continuously search information to act adaptively. Comparably, during expert search, a soccer goalkeeper trying to stop a penalty kick scans the penalty taker's body (e.g., the eyes, hips, legs, feet) for information that guides the decision of when and where to move.
In contrast to everyday environments, participants in a typical visual search research paradigm are seated and required to identify, as quickly as possible, an L among T's presented on a monitor. It is unlikely that this seated-monitor paradigm does justice to the intricacies of visual search in complex environments; this may be equally true for the associated models that presume that visual search proceeds on the basis of individual items (Treisman & Gelade Reference Treisman and Gelade1980). Conversely, Hulleman & Olivers' (H&O's) FVF model takes the fixation (and thus eye movements) as the central unit of visual search. This is an important step because it opens up the possibility to go beyond research paradigms that only require participants to (passively) watch screens. In particular, H&O's perspective potentially permits researchers to explicate the observed pick-up of global information that occurs when searching complex everyday environments (Diaz et al. Reference Diaz, Fajen and Phillips2012). However, to fully capture the richness of visual search in complex everyday environments, H&O's model would benefit from a thorough consideration of the functional characteristics of visual search.
If visual search functions to gather information for guiding our interactions with the environment, where the information resides and what action the information controls is of key concern. Gibson (Reference Gibson1979) asserted that information resides in structured energy arrays that surround us. For example, the optic array is the surrounding light patterned by reflection against the surfaces, objects and persons (including the observer!) of the environment. Hence, the structured light patterns are specific to, and inform about, the environment. Accordingly, perception is the pick-up of this information in the optic array. Thus, it is crucial to recognize that an observer always moves, even if these movements would be restricted to the eyes! The information the observer exploits is a continuous flux, but within these unceasing transformations some patterns remain unchanged or invariant. Broadly speaking, Gibson proposed that invariances specify the (unchanging) environment, while the changes specify how the observer relates to the environment; they inform the observer about the actions that the environment affords. This implies that the observer's body, head, and eye movements co-structure information for guiding the observer's interaction with the environment, and thus must be part of any unified account of visual search.
To illustrate let us return to the soccer goalkeeper trying to stop a penalty kick. Typically, the ball moves at a speed that leaves a goalkeeper insufficient time to decide which side to dive on the basis of ball flight information. Therefore the goalkeeper must anticipate the direction of the dive based on information that resides in the penalty taker's movements. Expert goalkeepers distinguish themselves from their less successful counterparts in how they visually search the penalty taker's body for gathering this information. They make a small number of fixations of longer duration to fewer locations (Savelsbergh et al. Reference Savelsbergh, Williams, van der Kamp and Ward2002). Intriguingly, they particularly make long fixations on the empty space in between the non-kicking leg and the ball instead of making a sequence of fixations between different locations (Piras & Vickers Reference Piras and Vickers2011). This finding concurs with analyses that the most reliable information is distributed across different body locations rather than being located at one joint or body part (Diaz et al. Reference Diaz, Fajen and Phillips2012). H&O's FVF model can easily accommodate these observations. Within the model the FVF is defined as “the area of the visual field around fixation from which a signal can be expected to be detected” (sect. 5.1, para. 2). Importantly, the field is not fixed but varies in size. The smaller the field, the more fixations are needed and the more time the observer needs to search. Accordingly, expert goalkeepers may have a larger FVF than less skilled goalkeepers, allowing them to exploit the distributed information with less extensive visual search. This skilled search behaviour potentially provides experts with more reliable and timely information for ball interception.
H&O's perspective is largely limited to (typical) seated-monitor paradigms, which address how eye movements are used to search the environment. Yet in complex everyday environments, eye movements are but one means of gathering information, as a person's search also relies heavily on head and (whole) body movements. The over-reliance on seated-monitor experimental tasks leads to a limited view of visual search and may especially obscure its functional aspects. Perception and action, even in an identical environment, exploit different information and induce different patterns of visual search (Van Doorn et al. Reference van Doorn, van der Kamp, de Wit and Savelsbergh2009). In this respect, we have previously reported that a soccer goalkeeper's visual search is fundamentally different when watching a penalty taker on a screen and verbally predicting kick direction compared to when actually facing a penalty taker in real-time and attempting to intercept the ball (Dicks et al. Reference Dicks, Button and Davids2010). Perhaps surprisingly, on the pitch less time appears to be spent searching the body, while fixation towards the ball increases. It is likely that the different functional requirements affect the spatio-temporal structure of visual search in many more ways than a change in the magnitude of the FVF. A crucial challenge for any account of visual search, including the FVF model, is to spell out in more detail how functional requirements systematically affect the eye, head, and body movements for gathering information in complex everyday environments. To this end, looking further than monitors is a necessity!
The primary function of visual search is to gather information for guiding actions with persons, objects, and events in everyday environments. For example, a pedestrian walking down a busy city street, and a police officer chasing a suspect are examples of complex everyday environments that require people to continuously search information to act adaptively. Comparably, during expert search, a soccer goalkeeper trying to stop a penalty kick scans the penalty taker's body (e.g., the eyes, hips, legs, feet) for information that guides the decision of when and where to move.
In contrast to everyday environments, participants in a typical visual search research paradigm are seated and required to identify, as quickly as possible, an L among T's presented on a monitor. It is unlikely that this seated-monitor paradigm does justice to the intricacies of visual search in complex environments; this may be equally true for the associated models that presume that visual search proceeds on the basis of individual items (Treisman & Gelade Reference Treisman and Gelade1980). Conversely, Hulleman & Olivers' (H&O's) FVF model takes the fixation (and thus eye movements) as the central unit of visual search. This is an important step because it opens up the possibility to go beyond research paradigms that only require participants to (passively) watch screens. In particular, H&O's perspective potentially permits researchers to explicate the observed pick-up of global information that occurs when searching complex everyday environments (Diaz et al. Reference Diaz, Fajen and Phillips2012). However, to fully capture the richness of visual search in complex everyday environments, H&O's model would benefit from a thorough consideration of the functional characteristics of visual search.
If visual search functions to gather information for guiding our interactions with the environment, where the information resides and what action the information controls is of key concern. Gibson (Reference Gibson1979) asserted that information resides in structured energy arrays that surround us. For example, the optic array is the surrounding light patterned by reflection against the surfaces, objects and persons (including the observer!) of the environment. Hence, the structured light patterns are specific to, and inform about, the environment. Accordingly, perception is the pick-up of this information in the optic array. Thus, it is crucial to recognize that an observer always moves, even if these movements would be restricted to the eyes! The information the observer exploits is a continuous flux, but within these unceasing transformations some patterns remain unchanged or invariant. Broadly speaking, Gibson proposed that invariances specify the (unchanging) environment, while the changes specify how the observer relates to the environment; they inform the observer about the actions that the environment affords. This implies that the observer's body, head, and eye movements co-structure information for guiding the observer's interaction with the environment, and thus must be part of any unified account of visual search.
To illustrate let us return to the soccer goalkeeper trying to stop a penalty kick. Typically, the ball moves at a speed that leaves a goalkeeper insufficient time to decide which side to dive on the basis of ball flight information. Therefore the goalkeeper must anticipate the direction of the dive based on information that resides in the penalty taker's movements. Expert goalkeepers distinguish themselves from their less successful counterparts in how they visually search the penalty taker's body for gathering this information. They make a small number of fixations of longer duration to fewer locations (Savelsbergh et al. Reference Savelsbergh, Williams, van der Kamp and Ward2002). Intriguingly, they particularly make long fixations on the empty space in between the non-kicking leg and the ball instead of making a sequence of fixations between different locations (Piras & Vickers Reference Piras and Vickers2011). This finding concurs with analyses that the most reliable information is distributed across different body locations rather than being located at one joint or body part (Diaz et al. Reference Diaz, Fajen and Phillips2012). H&O's FVF model can easily accommodate these observations. Within the model the FVF is defined as “the area of the visual field around fixation from which a signal can be expected to be detected” (sect. 5.1, para. 2). Importantly, the field is not fixed but varies in size. The smaller the field, the more fixations are needed and the more time the observer needs to search. Accordingly, expert goalkeepers may have a larger FVF than less skilled goalkeepers, allowing them to exploit the distributed information with less extensive visual search. This skilled search behaviour potentially provides experts with more reliable and timely information for ball interception.
H&O's perspective is largely limited to (typical) seated-monitor paradigms, which address how eye movements are used to search the environment. Yet in complex everyday environments, eye movements are but one means of gathering information, as a person's search also relies heavily on head and (whole) body movements. The over-reliance on seated-monitor experimental tasks leads to a limited view of visual search and may especially obscure its functional aspects. Perception and action, even in an identical environment, exploit different information and induce different patterns of visual search (Van Doorn et al. Reference van Doorn, van der Kamp, de Wit and Savelsbergh2009). In this respect, we have previously reported that a soccer goalkeeper's visual search is fundamentally different when watching a penalty taker on a screen and verbally predicting kick direction compared to when actually facing a penalty taker in real-time and attempting to intercept the ball (Dicks et al. Reference Dicks, Button and Davids2010). Perhaps surprisingly, on the pitch less time appears to be spent searching the body, while fixation towards the ball increases. It is likely that the different functional requirements affect the spatio-temporal structure of visual search in many more ways than a change in the magnitude of the FVF. A crucial challenge for any account of visual search, including the FVF model, is to spell out in more detail how functional requirements systematically affect the eye, head, and body movements for gathering information in complex everyday environments. To this end, looking further than monitors is a necessity!