Introduction

The executive function (EF) construct encompasses a set of higher-order cognitive abilities such as the organizational, control, and self-regulation skills necessary for goal direction (Cristofori, Cohen-Zimerman & Grafman, 2019; Figueras et al., 2008). It has been reported that people with hearing loss may have a higher risk factor for developing and consolidating some of these executive functions (Mason et al., 2021; Conway, Pisoni & Kronenberger, 2009; Pisoni & Cleary, 2003). No agreement yet on the consequences of the hearing loss itself or the social and personal restrictions are underlying the barrier to communication with others (Corina & Singleton, 2009) or in addition to other factors such as the etiology of hearing loss and sociocultural context.

Particularly some researchers have exposed differences in attention skills (Bavelier et al., 2000a; Hauser et al., 2007; Thakur et al., 2019; Tharpe et al., 2008; Zeni et al., 2020) in working memory tasks (Burkholder & Pisoni, 2003; Pisoni & Cleary, 2003), inhibitory control, (Mason et al., 2021), and sensorimotor synchronization (Petry et al., 2018; Tranchant et al., 2017). However, there is evidence for some auditory deprivation-dependent brain changes that may be related to functional and adaptive behaviors (Kral et al., 2016). Indeed, it has been hypothesized that hearing loss has effects beyond auditory processing and may affect cognitive functions related to sequentially and temporality since hearing is the primary sensory pathway for perceiving high-level sequential patterns that change in time rather than space (Conway et al., 2009). That is, that audition leads to the establishment of temporal ordering that underlies expectation and anticipation, what comes before and what happens next? For example, a subdomain of working memory attends to this temporality, as will be discussed below. It appears that deaf individuals, especially those who have not acquired language early, there may be more difficult in consolidating functions related to learning sequentially.

On the other hand, and in contrast to the above, it seems that once the sign language is consolidated there are increases in subdomains of some functions, for example, in peripheral attention processes, that underlie inhibitory control (Bosworth & Dobkins, 2002), this makes sense given that a visuospatial language such as sign language develops spatially, supported more by visual and proprioceptive processes. This is consistent with the Enhanced Hypothesis proposed by Rodger et al., (2021) and Sidera et al., (2017) which states that in the absence of hearing the visual system would have a more significant visual function. However, Dye, Hauser & Bavelier (2009) suggest that hearing deprivation is not a causal factor for presenting difficulties in cognitive processes, such as attention, but that these may be a consequence of other factors that have nothing to do with deafness per se since it is essential to take into account aspects such as the etiology of deafness, sociocultural factors, the age of acquisition of a communicative system, and even the modality in which this is consolidated, that is, whether it is a sign language or an oral language. Even the results that show differences in some cognitive domains are different in children and adults because the consolidation of neurodevelopmental milestones seems to depend largely on the acquisition of a communicative system, without conclusive evidence on the issue, mainly because of the dynamism that characterizes cognition and that must be considered in technological development.

Technological development has allowed converging lines of research related to the deaf population, emphasizing on time advance related to assistive technologies, especially those focused on communication. Assistive technologies are defined as those developments, software, or products that allow for to increase, maintain, or improve some functional capabilities in people with disabilities, for example, prosthetic pieces, hearing aids, screen readers, or wheelchairs, among others. Its main function is to assist the person to be as independent as possible. Most of the literature linking technology and deafness is focused on these types of devices, especially those developments to reduce communication challenges (Landolfi et al., 2022; Imran, et al., 2021; Jacob, et al, 2021; Albrecht, Jungnicke & von Jan, 2015).

For this paper we focus on technological advances that in recent years have made it possible to adapt devices and methodologies for different populations, allowing a better understanding of the cognitive processes mediated by hearing, but not since an assistance idea or to facilitate communication between deaf and hearing people. On the other hand, the design of technological tools where there is an outstanding commitment to the interaction with digital environments promotes better behavior and motivation in users, giving an advantage to the evaluation processes to be more dynamic compared to other traditional ones.

This review is divided into three parts. The first part shows a brief description of the executive and cognitive functions; in part two we will give an account of the use of technologies such as interfaces and biometric devices, and the development or adaptation of software for the assessment of these functions. Finally, we conclude with a summary and perspectives on future applications and considerations for developing or adapting technological devices that complement the assessment of executive functions in the deaf population.

We introduce a qualitative literature review to explore if there are technological devices that evaluate executive functions or at least one of them, to show alternatives or complement neuroimages techniques or neuropsychological batteries, especially for the difficulties explained before the communication barrier. For this review, we exclude assistance or teaching devices, because the goal was not to evaluate this competence or the design adaptation for physical or communication nor aid hearing. The cochlear implant variable or another hearing aid did also not include because is documented that the cognitive process is usually different in people with hearing aid (van Wieringen et al., 2019; Hua, et al., 2017).

1. Cognitive and executive functions

The construct of executive and cognitive functions has been coined from different perspectives over time. Lezak (1982) distinguished both based on what was intended to be known for each function. To describe cognitive functions, the author emphasized how much knowledge or skills the person possessed; for example, what skills remained intact or were impaired in people, or how well they performed a task compared to another, and on the other hand, executive functions are related to whether people do something or not, i.e., they focus on execution and what is related to it. Barkley (2012) contributes to this meaning by indicating that executive functioning underlies how a person achieves a goal efficiently. Lezak (1982) indicates that we should ask ourselves: ask how well the patient maintains a performance rate, how consistently and effectively he self-corrects, and how responsive to changes in the demands of the task, for example.

Recently, executive functions (EFs) have been described as a series of mental processes necessary to be attentive, solve problems, reason, have self-control, and persist in a task (Blankenship et al., 2019; Kral et al., 2016). According to some authors, EFs are framed in three central components, and, from them, other dimensions are derived that are supported by the first ones: working memory, inhibitory control, and cognitive flexibility (Diamond, 2020; Diamond, 2013), Cristofori, Cohen-Zimerman & Grafman, (2019) also include planning, reasoning and problem-solving. For this review, we consider the three central components and the subparts or dimensions associated with each of them, especially attention, which is framed within inhibitory control and seems to be the most studied and controversial function in deaf people.

Inhibitory control is required to control behaviors, thoughts, and emotions, and to adapt actions to emit or not a response. It is therefore strongly linked to cognitive control and working memory (Cristofori et al., 2019). This ability supports attention because it is necessary to inhibit external and internal factors and sustain attention to achieve specific goals. Attention is understood as the ability to filter, select, and focus on various elements of the environment (Dye, Hauser & Bavelier, 2008). To this effect, Hauser, Lukomski & Hillman (2008) indicate that inhibition is one of the major cognitive skills because it models motor and behavioral control. It has recently been theorized that inhibitory control is not a single unit, but is composed of a series of functions, among which two main ones are differentiated, response inhibition, which refers to the ability to control impulsive behavior to prevent (inhibit) motor and verbal responses, and interference suppression that involves working memory and refers to the ability to suppress interfering information (Daza González et al., 2021).

Working memory (WM) involves the ability to retain information in the short term, even when it is not perceptually present, as well as the ability to manipulate that information before it passes into long-term memory (Diamond, 2020; Baddeley, 2017). Two types of WM are generally distinguished, visuospatial and verbal. WM is critical for making sense of anything that unfolds over time, for that always requires holding in mind what happened earlier and relating that to what comes later (Diamond, 2013). The reasoning is closely linked to WM because you need to have the information online long enough to be able to manipulate it and act accordingly.

Lastly, cognitive flexibility is built on WM and inhibitory control and is defined as the ability to adapt in the face of environmental change and to generate new ideas that drive innovation and promote growth and discovery (Cristofori et al., 2019; Badre and Wagner, 2006). Cognitive flexibility is associated with an ability to adapt to changing conditions in the environment, which is why it requires control and manipulation of information to know new strategies.

Some researchers have been exposed to differences in EFs in deaf people, in particular in attention skills (Zeni et al., 2020; Thakur et al., 2019; Tharpe et al., 2008; Hauser et al., 2007; Bavelier et al., 2000b); the execution of tasks of working memory (Mason et al., 2021; Cardin et al., 2018; López-Crespo et al., 2012; Burkholder & Pisoni, 2003; Pisoni & Cleary, 2003), and inhibitory control (Mason et al., 2021). It seems to be that some executive skills are so close to the linguistic domain that are delayed consolidating (Figueras et al., 2008), maybe because deaf people acquire a late sign language, opposite to oral language that is developed since birth. Often, deaf children do not have access to a language at birth due to the majority being born in a hearing family or because the educational system does not give them an effective early intervention in sign language (Krebs et al., 2021). Thus, the sociocultural context also seems to affect the development and consolidation of some EFs, especially when a deaf child is born into a hearing family environment.

On the other hand, EFs seem to be linked with the fact that, when there is sensorial deprivation, the remaining senses appear to be more accurate, which is consistent with the Sensorial Compensation Hypothesis (Pavani & Bottari, 2012). Whereas where in the case of deafness, vision, and tactile sense are more sensitive to inputs from the environment. From the neurocognitive perspective, this is due to the brain’s ability to reorganize connectivity to other areas that are not affected by the sensory loss, in this case, there is a major recruitment of visual and tactile areas, although this process of neuroplasticity depends on variables such as the environment, age of onset of deafness and even interindividual factors that influence brain adaptation to sensory loss (Kral et al., 2016). The authors emphasize the possibility that, as the brain is a dynamic system that bases its development on experiences between neural activity and stimulation from the environment, a sensory loss could affect, positively or negatively, domains beyond hearing. This could be concordant with an enhancement in attention skills, for example. The case of disturbance in inhibitory control and working memory seems to be based on hearing feedback, which is coincident with Auditory Scaffolding proposed by (Conway et al., 2009) where some cognitive domains are underlying in sound perception, especially that based on temporally and sequential processing, like working memory.

2. Use of technology to assess cognitive domains in Deaf people

One of the most common methods to assess EFs is through neuropsychological tools. However, in the case of deaf people, there are two main factors to take into consideration: first, the communication barrier, since most of the batteries are designed for hearing people, and second, the consideration of the delay in language acquisition as a risk factor for the consolidation of cognitive functions. A systematic review by Vázquez Mosquera (2021) indicated that there are no rigorous instruments with special adaptations to assess deaf children, in this case. This could be a reason that some authors combine technology and assessment cognitive functions. We found design research for deaf children, named AWARD Neuropsychological battery, developed by González et al., (2011) that explores cognitive areas from tasks executed in a web application, where they can configure the language depending on user preference, for their research, could be Lengua de Signos Española (LSE) or oral language. This software tool allows making a cognitive profile of deaf children by implementing a battery of neuropsychological tests using adaptive web technology, whose main utility would be that professionals in neuropsychology can make use of this tool to minimize communication barriers. It should be noted that, although technological devices are accurate in detecting and evaluating cognitive functions, the design of tasks/paradigms should be more sensitive to detect changes in what is to be evaluated, considering that no brain function occurs in isolation, but rather the sum of interactions of various processes.

Based on the literature consulted for this review and taking into consideration that the exploration of EFs in deaf people is less explored compared to studies conducted on hearing people, the studies found so far in this review are described. The sections are divided according to the classification of assessment tools used by the authors of the studies. However, we know that each one had a different population of studies, in terms of adults and children, so we try to limit them to deaf people without cochlear implants, although we emphasize that we cannot generalize the results to the entire deaf population, since the heterogeneity of people must be considered. Within the literature review, we found a wide variety of technological devices that can be used to assess EFs, without most of them being necessarily designed for the deaf population, but rather have been adapted from traditional use in research in other populations and where the paradigms have been adapted by interpreting the instructions into some sign language, for example. That is the reason why the studies shown in this review include technological developments that can be classified as biometric devices, physical and digital interfaces, and video games. This review is an attempt to link the use of technological devices to assess these functions and to give a prospective scenario for future developments and applications. The papers reviewed are in Table 1.

3. Discussion

Interest in research on cognition in deaf people has been increasing in recent years, not only from the perspective of assistive, recognition, or educational devices but also for research and educational purposes. The evaluation of cognitive processes in deaf people allows inferences to be made from different perspectives:

From cognition. From the evaluation of different domains, it is possible to have deep knowledge about the differences in cognitive processes derived from hearing, which would be framed within the Cognitive Hearing Science proposed by Arlinger et al., (2009) that is aligned with an interdisciplinary approach between cognition and hearing. Maybe, although it may seem contradictory, from this field it is possible to rethink and rephrase approaches and research aimed at deaf people.

One of the limitations present in the reviewed articles is the heterogeneity of the population even between children and adults. The different etiologies and thresholds of hearing loss do not allow generalizations of the results to establish precise approximations about the development of executive functions. Although deafness is a risk factor for the development and consolidation of these functions, there is no consensus on whether deafness per se affects cognitive functioning or whether it is derived from the socio-cultural context, influenced by a lower interaction with the environment due to communication barriers; it has even been reported that deaf people have lower prosocial behaviors compared to their hearing peers.

This is also mentioned by Hauser, Lukomski & Hillman (2008), who argue that in most studies with deaf people, there is no care to select participants and that they are truly representative of the deaf community, so variables such as the age of acquisition of a sign language, socio-cultural context or etiology of deafness should be considered.

The evidence shows that there are differences between deaf and hearing people and that these differences do not imply disadvantages or negative issues for cognition in deaf people but seem to exhibit other types of strategies for the appropriation of the world, such as attentional or visual resources, like Daza González et al., (2021) proposed in their research. In this sense, we agree with the reflection of Marschark & Hauser (2008) that there is a misconception about the cognition of deaf people and what it is to be Deaf, which leads to a series of barriers in different areas such as work, school, social and even family.

One of the EFs that seems to have the greatest difficulty in consolidation is working memory, especially in deaf children. Understanding that differences in this function may underlie learning in mathematics, reading, coordination in motor skills, abstract concept formation, and categorization should be basic to better academic achievement, for example. Auditory experience provides temporal patterns that help develop the above skills, so it would be expected that Deaf children would show difficulties in consolidating areas related to sequential processing, but this is not general for all people. On the other hand, several authors describe advantages in visual processes, particularly those referred to as peripheral visual attention, with emphasis on people who have already acquired sign language, perhaps because visuospatial languages develop in space. However, this visual advantage may entail difficulty in deaf children, because, not having developed inhibitory control, it is common for them to be labeled as distractible or inattentive, although the cognitive basis indicates otherwise. It is imperative to note that one of the variables that stands out as a differentiator in the development of EFs is the early acquisition of sign language. In different contexts, it is known that children are the first generation of deaf people in their hearing family, which hinders the acquisition of a mother tongue in the first years of life, and it is not until a later age that children can have access to sign language. It is worth noting that at this point we would no longer speak strictly of language acquisition, which would occur spontaneously in a natural context (Krashen, 1982), but of language learning, where there is an express search for the linguistic forms to be used and which will allow access to communication resources (Muntzel, 1995).

Understanding the basis of the cognitive dimensions in the deaf population allows them to rethink conceptions about their abilities, to design educational strategies that enhance the advantages and help those domains with greater difficulty, and although it is emphasized that neither the results nor the inferences are generalizable to the entire deaf population, it can be a starting point for lines of research and action.

From technology. The use of digital devices seems to be increasing for the evaluation of different cognitive processes. In this sense, and within the biometric data devices, the use of eye trackers seems to be the most usual, based on the premise that deaf people have different visual strategies than hearing people, due to the expanded use of space by the form of visuospatial communication. This, however, seems to be mediated by the consolidation of a communicative system, so in people who have not consolidated one, there seem to be differences in the results. This should be considered in the methodological conception to obtain the greatest homogeneity even when there is variability in the participants. One of the advantages of using technological devices to assess EFs is that they can provide more precise information about domains that may not be so evident in a traditional observation. This does not imply that assessment methods such as neuropsychological batteries should be replaced, but perhaps they can be complemented with other types of data that provide additional information for a better understanding of cognition. On the other hand, several authors refer to the use of a single sensory modality for the design of paradigms, so that integrating other sensory resources can provide more information about the processing of different cognitive functions. The current use of gamification seems to open possibilities of conjunction between learning and evaluation through a sense of playfulness, which brings other challenges in usability. As a future scope, the next revision could integrate virtual reality applications.

The development of technologies has been increasing and has diversified towards different needs of the deaf population. On the one hand, as teaching tools, to eliminate communication barriers by designing recognition devices or interfaces; others as assistive technologies based on electronic devices such as hearing aids or amplifiers, and the ones we focus on in this review, designs focused on the assessment of cognitive skills.

Conclusion

The diversity of the use and adaptations of technologies shows the need to implement this type of device as a means, either complementary or primary, for the evaluation of skills and functions related to cognition and that move away from traditional methodologies. Perhaps a line of research that can provide accurate approximations of the development of executive functions is focused on the study and evaluation of different cognitive strategies and tools that would be mediated by the absence of auditory input. In this sense, assessment through technology offers the opportunity to observe and make estimates about cognitive domains and subdomains in deaf people. Although there is ample evidence of the use of standardized systems, such as the eye tracker, or some interfaces, such as the Gordon System Diagnostic, we identified that there are other devices that have not been validated in large populations, which is a limitation mentioned by the authors themselves. Another observation is that there is evidence that combining devices with other types of technologies, can yield more information on how and in what intensity the functions being evaluated occur (Pop-Jordanova & Pop-Jordanov, 2020). Approaches that integrate these parameters can be used to obtain more accurate, sensitive, and specific cognitive level indices. The development of technologies must then consider the interindividual, etiologies, heterogeneity, and sociocultural contexts in which Deaf people develop, and as a prospective scenario based on the above, consider interdisciplinary and collaborative work with the Deaf community itself to provide real and functional results that converge technological innovation and Cognitive Hearing Science.