The recognition of co-occurrence of AD/HD with ASD is aptly captured in DSM-5 which permits comorbid diagnoses of both conditions. Indeed, studies have found similar structural brain abnormalities in those with ASD and AD/HD when compared to controls (Matson, Rieske, & Williams, 2013). In contrast to this literature, diagnostic criteria in the DSM-IV reflected the historical view that a diagnosis of ASD preempts and therefore precludes an additional diagnosis of AD/HD. This historical assumption is no longer considered valid as it was revisited and changed in the DSM-5 which permits comorbid diagnosis (Matson et al., 2013). Research indicates that AD/HD and ASDs are co-occurring 14–78 % (Gargaro et al., 2011). This is a wide range but indicates that many individuals with ASD struggle with attention problems. For this reason, it is very important to thoroughly assess attention skills when evaluating for an ASD.

As will be comprehensively reviewed in the Chap. 13, differential diagnosis of AD/HD requires an assessment of disinhibition and social reciprocity. If the child is disinhibited and lacks social reciprocity, he or she likely has both AD/HD and ASD. Mayes et al. (2012) state that ASD and AD/HD are “neurobiological disorders with similar underlying neuropsychological deficits.” (p. 283) Children with comorbid symptoms have more difficulty inhibiting inappropriate responses when compared with children who have ASD alone (Mannion & Leader, 2013). Those with ASD alone demonstrate better inhibition, flexibility, working memory, and planning skills than those with comorbid diagnosis (Sinzig, Bruning, Morsch, & Lehmkuhl, 2008) although these skills are still often challenging. Deprey and Ozonoff & Corbett et al. (2009) found that hyper vigilant attention and internal distractibility are more common in ASD while lack of focus and distractibility by external stimuli is characteristic of AD/HD.

The authors of this text observe that many children with ASD exhibit intermittent challenges with attention and executive functioning skills while those with comorbid diagnoses have significant deficits in sustained attention, inhibition, and focus. Individuals with AD/HD who do not have ASD may have some social challenges influenced by impulsivity, inattention, and hyperactivity. However, when focused, individuals with only AD/HD should be able to engage in pretend play and creative activities like telling a story or acting out a cartoon. Children with ASD alone tend to have less pervasive problems with attention. They can attend when given appropriate reinforcement. Sustained attention can be assessed via continuous performance testing and with rating scales completed by parents, teachers, and individuals. These may include the TOVA, BASC-2, BRIEF, or Conners AD/HD scales.

Attention can be broadly defined as information processing mechanisms that mediate perceptual selectivity (Keehn, Shih, Brenner, Townsend, & Müller, 2013). Problems with attention have historically been considered as an associated or secondary deficit when present with ASD. Research reveals, however, that impairments represent early and lifelong abnormalities in efficiently modulating attention networks for individuals with ASD (Keehn, Müller & Townsend, 2013).

Attention mechanisms represent the confluence of external stimuli processed through bottom-up, sensory afferent nerve signals received in the posterior brain regions as well as internal, goal-directed processes originating in the anterior/frontal brain regions and executed through efferent, top-down signals (Kandel, Schwartz, & Jessell, 1991). Sensory processing assessment and therapies (Ayres, 2005) focus on the former bottom-up processes while behavior analytic assessments (Iwata et al., 1990) and therapies focus on both processes through classical and operant conditioning paradigms (Barlow, 2002; Cooper, Heron, & Hewerd, 2013).

In light of the fact that millions of brain fibers are sensory processing assessment and therapies (Ayres, 2005) focus on the former bottom-up processes while behavior analytic assessments (Iwata et al., 1990) and therapies focus on both processes through classical and operant conditioning paradigms. In light of the fact that millions of brain fibers are connecting the posterior and anterior cortical regions, perceptual selectivity or attention rarely consists exclusively of top-down or bottom-up processes but rather successful and adaptive information processing requires the integration of both processes (Keehn et al., 2013).

As previously mentioned, AD/HD and ASDs co-occur in a wide range of 14–78 % of the population diagnosed with ASD (Gargaro et al., 2011). Such a range in findings likely reflects that, in addition to the wide ASD span of various symptoms and severities, attention problems are multifaceted and responsible for a distinct set of cognitive processes. These processes include alerting, orienting, and executive control networks (Petersen & Posner, 2012; Posner & Petersen, 1989). Furthermore, research on attention indicates that attention networks each have their own developmental trajectories resulting in the emergence and strengthening of various attention skills into adulthood. Often these trajectories are delayed or attention skills may be present but significantly less efficient for individuals with ASD. All these complexities emphasize the importance of individually assessing for the occurrence and nature of attention deficits when evaluating for an ASD.

The authors of this text observe that most individuals with ASD exhibit challenges with attention and executive functioning skills evidenced in selective attention to highly preferred interests or activities and/or problems with flexibility, ideational fluency, planning, or central coherence. Nonetheless, those with ASD and not AD/HD demonstrate better inhibition, flexibility, working memory, and planning skills than those with both ASD and AD/HD (Sinzig et al., 2008). Individuals with comorbid diagnoses of ASD and AD/HD have additional deficits in sustaining attention in the absence of immediate reinforcement. Individuals with AD/HD but not ASD may exhibit some social challenges as a result of being impulsive, inattentive, or hyperactive. Such social difficulties look different and may appear like obnoxiousness, impulsive aggressive acts toward peers, and a lack of body awareness that could interfere with social functioning. Some children with AD/HD may have some difficulty understanding emotions, challenges with rejection or academic punishment for over-active behavior, or even failed friendships from impulsive aggression. When focused, however, individuals with only AD/HD should be able to engage in reciprocal activities such as pretend play or conversation and they should exhibit synchronized verbal and gestural communication in creative activities such as telling a story or acting out a cartoon. The following discussion provides further details on attentional networks, skills, developmental trajectories, and comorbid deficits found with ASD. In addition, assessment measures appropriate for each attention process as well as recommendations for associated weaknesses or deficits are included.

The alerting network is responsible for achieving and maintaining a state of sensitivity to incoming information (Keehn et al., 2013). Parents can attest to the fact that newborn infants respond only to internal information such as hunger or pain and often actually sleep best when there is a high level of external noise or activity. Such endogenous wakefulness is referred to as tonic alertness and describes general arousal. Tonic alertness in infants develops rapidly between 2 and 24 weeks. Subsequently, the autonomic nervous system continues to develop across the life span. Research on persons with ASD indicates the possibility of separate subgroups representing individuals with either hyper- or hypo-arousal . These two disparate subgroups are captured in the ADOS assessment where the examiner may observe and record the participant’s overall level of engagement, attention, excitability, and alertness ranging from over-responsive to lethargic. Clinically, individuals with ASD and hyperarousal are subject to being easily distracted by any form of internal or external stimuli and likely also meet criteria for AD/HD. Deprey and Ozonoff & Corbett et al. (2009) found that lack of focused attention skills and distractibility by external stimuli is characteristic of AD/HD. Furthermore, Mayes et al. (2012) found that children with comorbid symptoms of both ASD and AD/HD have more difficulty with inhibitory performance when compared with children who have ASD alone (Mannion & Leader, 2013) which may again reflect the hyperarousal subgroup. Alternately, some have hypothesized that chronic hyperarousal may actually result in increased overselective attention (Liss, Saulnier, Fein, & Kinsbourne, 2006); a tendency to perseveratively regard, review or rehearse high preference internal or external stimuli.

The second component of the alerting network is phasic alertness which refers to a transient response to a behavioral or experimental cue (Keehn et al., 2013). This is a reflexive physiological response to a change in the environment rather than a volitional reaction. Phasic alertness is modulated by the level of tonic alertness and tonic alertness or overall arousal influences task performance. Phasic orienting responses develop rapidly during the first year of life, efficiency, and speed of phasic alerting appear to develop into early school-age years, and may reach adult levels by age 7–8 years of age (Cycowicz, Friedman, & Rothstein, 1996). Electrophysiological measures have demonstrated atypical phasic alerting in individuals with ASD and findings suggest modulation of phasic alerting mechanisms may be dysfunctional in ASD (Keehn et al., 2013). This in turn is likely related to marked insensitivity to novel stimuli often seen in individuals with ASD.

Assessment of response to novel stimuli can be gleaned from the Wechsler Cancellation and Symbol Search tasks . Like most assessment tasks or protocols, these measures assess multiple constructs; the Symbol Search also being a measure of processing speed. Nonetheless, observation and review of the quality of performance, specifically, any errors, and the type of errors, can shed light on whether they are insensitive to novel stimuli. Parents or family members may also express concern that the individual with ASD ignores presents under the Christmas tree or fails to notice a new student in the classroom. A partner may complain their mate with ASD does not notice droopy plants that need watering or a special outfit they wear. These challenges may reflect problems with phasic orienting.

Conversation activities from the ADOS as well as clinical observations to the examiner’s verbal efforts to build rapport can shed light on the participant’s response to novel auditory stimuli. If a verbally fluent participant fails to comment appropriately or at all when the topic of conversation changes, even in the absence of emotional content, it may be indicative of a fundamental impairment in phasic orienting. The Cancellation and Symbol Search subtests combine with other measures to assist in assessing focused attention skills more generally. The Comprehensive Trail Making Test may yield valuable information on the participant’s distractibility to various visual stimuli.

The voluntary maintenance of alertness in the absence of immediate reinforcement is called sustained attention. Sustained attention increases rapidly from 2 to 6 months of age (Richards, 1997); and then increases significantly again from 3 to 6 years of age; continuing to develop into late childhood and adolescence, and reaching adult-like levels around 12 years of age (Lin, Hsiao, & Chen, 1999). Deficits in sustaining attention are often present within the population of individuals with ASD and, when present, warrant the added diagnosis of AD/HD either Inattentive or Combined Type. Sustained attention can be assessed directly via continuous performance testing (CPT) using the TOVA or Gordon. Subjective rating scales can be helpful; completed by parents, teachers, and individuals, including: BASC-2 or Conners’ AD/HD scales or the CBCL. Continuous performance testing measures are advantageous for providing computer captured reaction time, variations in reaction time as well as errors of omission and commission. While rating scales are clearly influenced by the perceptions of the rater, they do afford the possibility of obtaining information about the participant in other environments beyond the testing room.

Posner and Petersen (1989) included the executive control networks in their conceptualization of attention. Clearly, many elements of executive control including set-shifting, inhibition, and working memory are relevant in any discussion on attention. These constructs are included in the discussion on Executive Functioning.