confirmed by diagnostic testing. a ucapi total score is calculated by combining the totals from the six listening conditions and provides an overall value to categorize listening abilities. additionally, analysis of the scores from the six listening conditions provides an auditory profile for the subject. each listening condition can then be utilized by the professional in making recommendation for diagnosing problem of learning through listening and treatment decisions. the ucapi provides information on listening problems in various populations that can aid examiners in making recommendations for assessment and management. apd has been defined anatomically in terms of the integrity of the auditory areas of the nervous system. however, children with symptoms of apd typically have no evidence of neurological disease and the diagnosis is made on the basis of performance on behavioral auditory tests. auditory processing is "what we do with what we hear", and in apd there is a mismatch between peripheral hearing ability (which is typically normal) and ability to interpret or discriminate sounds. thus in those with no signs of neurological impairment, apd is diagnosed on the basis of auditory tests. there is, however, no consensus as to which tests should be used for diagnosis, as evidenced by the succession of task force reports that have appeared in recent years. the first of these occurred in 1996. this was followed by a conference organized by the american academy of audiology. experts attempting to define diagnostic criteria have to grapple with the problem that a child may do poorly on an auditory test for reasons other than poor auditory perception: for instance, failure could be due to inattention, difficulty in coping with task demands, or limited language ability. in an attempt to rule out at least some of these factors, the american academy of audiology conference explicitly advocated that for apd to be diagnosed, the child must have a modality-specific problem, i.e. affecting auditory but not visual processing. however, a committee of the american speech-language-hearing association subsequently rejected modality-specificity as a defining characteristic of auditory processing disorders. definitions in 2005 the american speech-language-hearing association (asha) published "central auditory processing disorders" as an update to the 1996 "central auditory processing: current status of research and implications for clinical practice". the american academy of audiology has released more current practice guidelines related to the disorder. asha formally defines apa as "a difficulty in the efficiency and effectiveness by which the central nervous system (cns) utilizes auditory information." in 2018, the british society of audiology published a "position statement and practice guidance" on auditory processing disorder (apd) updated its definition of apd. according to the society, apd refers to the inability to process speech and on-speech sounds. auditory processing disorder can be developmental or acquired. it may result from ear infections, head injuries or neurodevelopmental delays that affect processing of auditory information. this can include problems with: "...sound localization and lateralization (see also binaural fusion); auditory discrimination; auditory pattern recognition; temporal aspects of audition, including temporal integration, temporal discrimination (e.g., temporal gap detection), temporal ordering, and temporal masking; auditory performance in competing acoustic signals (including dichotic listening); and auditory performance with degraded acoustic signals". the committee of uk medical professionals steering the uk auditory processing disorder research program have developed the following working definition of auditory processing disorder: "apd results from impaired neural function and is characterized by poor recognition, discrimination, separation, grouping, localization, or ordering of speech sounds. it does not solely result from a deficit in general attention, language or other cognitive processes." types of testing the scan-c for children and scan-a for adolescents and adults are the most common tools for screening and diagnosing apd in the usa. both tests are standardized on a large number of subjects and include validation data on subjects with auditory processing disorders. the scan test batteries include screening tests: norm-based criterion-referenced scores; diagnostic tests: scaled scores, percentile ranks and ear advantage scores for all tests except the gap detection test. the four tests include four subsets on which the subject scores are derived include: discrimination of monaurally presented single words against background noise (speech in noise), acoustically degraded single words (filtered words), dichotically presented single words and sentences. random gap detection test (rgdt) is also a standardized test. it assesses an individual's gap detection threshold of tones and white noise. the exam includes stimuli at four different frequencies (500, 1000, 2000, and 4000 hz) and white noise clicks of 50 ms duration. it is a useful test because it provides an index of auditory temporal resolution. in children, an overall gap detection threshold greater than 20 ms means they have failed and may have an auditory processing disorder based on abnormal perception of sound in the time domain. gaps in noise test (gin) also measures temporal resolution by testing the patient's gap detection threshold in white noise. pitch patterns sequence test (ppt) and duration patterns sequence test (dpt) measure auditory pattern identification. the pps has s series of three tones presented at either of two pitches (high or low). meanwhile, the dps has a series of three tones that vary in duration rather than pitch (long or short). patients are then asked to describe the pattern of pitches presented. masking level difference (mld) at 500 hz measures overlapping temporal processing, binaural processing, and low-redundancy by measuring the difference in threshold of an auditory stimulus when a masking noise is presented in and out of phase. the staggered spondaic word test (ssw) is one of the oldest tests for apd developed by jack katz. although it has fallen into some disuse by audiologists as it is complicated to score, it is one of the quickest and most sensitive tests to determine apd. modality-specificity and controversies the issue of modality-specificity has led to considerable debate among experts in this field. cacace and mcfarland have argued that apd should be defined as a modality-specific perceptual dysfunction that is not due to peripheral hearing loss. they criticise more inclusive conceptualizations of apd as lacking diagnostic specificity. a requirement for modality-specificity could potentially avoid including children whose poor auditory performance is due to general factors such as poor attention or memory. others, however, have argued that a modality-specific approach is too narrow, and that it would miss children who had genuine perceptual problems affecting both visual and auditory processing. it is also impractical, as audiologists do not have access to standardized tests that are visual analogs of auditory tests. the debate over this issue remains unresolved between modality-specific researchers such as cacace, and associations such as the american speech-language-hearing association (among others). it is clear, however, that a modality-specific approach will diagnose fewer children with apd than a modality-general one, and that the latter approach runs a risk of including children who fail auditory tests for reasons other than poor auditory processing. although modality-specific testing has been advocated for well over a decade, the visual analog of apd testing has met with sustained resistance from the fields of optometry and ophthalmology. another controversy concerns the fact that most traditional tests of apd use verbal materials. the british society of audiology has embraced moore's (2006) recommendation that tests for apd should assess processing of non-speech sounds. the concern is that if verbal materials are used to test for apd, then children may fail because of limited language ability. an analogy may be drawn with trying to listen to sounds in a foreign language. it is much harder to distinguish between sounds or to remember a sequence of words in a language you do not know well: the problem is not an auditory one, but rather due to lack of expertise in the language. in recent years there have been additional criticisms of some popular tests for diagnosis of apd. tests that use tape-recorded american english have been shown to over-identify apd in speakers of other forms of english. performance on a battery of non-verbal auditory tests devised by the medical research council's institute of hearing research was found to be heavily influenced by non-sensory task demands, and indices of apd had low reliability when this was controlled for. this research undermines the validity of apd as a distinct entity in its own right and suggests that the use of the term "disorder" itself is unwarranted. in a recent review of such diagnostic issues, it was recommended that children with suspected auditory processing impairments receive a holistic psychometric assessment including general intellectual ability, auditory memory, and attention, phonological processing, language, and literacy. the authors state that "a clearer understanding of the relative contributions of perceptual and non-sensory, unimodal and supramodal factors to performance on psychoacoustic tests may well be the key to unravelling the clinical presentation of these individuals." depending on how it is defined, apd may share common symptoms with add/adhd, specific language impairment, and autism spectrum disorders. a review showed substantial evidence for atypical processing of auditory information in children with autism. dawes and bishop noted how specialists in audiology and speech-language pathology often adopted different approaches to child assessment, and they concluded their review as follows: "we regard it as crucial that these different professional groups work together in carrying out assessment, treatment and management of children and undertaking cross-disciplinary research." in practice, this seems rare. to ensure that apd is correctly diagnosed, the examiners must differentiate apd from other disorders with similar symptoms. factors that should be taken into account during the diagnosis are: attention, auditory neuropathy, fatigue, hearing and sensitivity, intellectual and developmental age, medications, motivation, motor skills, native language and language experience, response strategies and decision-making style, and visual acuity. it should also be noted that children under the age of seven cannot be evaluated correctly because their language and auditory processes are still developing. in addition, the presence of apd cannot be evaluated when a child's primary language is not english. characteristics the american speech-language-hearing association state that children with (central) auditory processing disorder often: have trouble paying attention to and remembering information presented orally, and may cope better with visually acquired information have problems carrying out multi-step directions given orally; need to hear only one direction at a time have poor listening skills need more time to process information have difficulty learning a new language have difficulty understanding jokes, sarcasm, and learning songs or nursery rhymes have language difficulties (e.g., they confuse syllable sequences and have problems developing vocabulary and understanding language) have difficulty with reading, comprehension, spelling, and vocabulary apd can manifest as problems determining the direction of sounds, difficulty perceiving differences between speech sounds and the sequencing of these sounds into meaningful words, confusing similar sounds such as "hat" with "bat", "there" with "where", etc. fewer words may be perceived than were actually said, as there can be problems detecting the gaps between words, creating the sense that someone is speaking unfamiliar or nonsense words. in addition, it is common for apd to cause speech errors involving the distortion and substitution of consonant sounds. those with apd may have problems relating what has been said with its meaning, despite obvious recognition that a word has been said, as well as repetition of the word. background noise, such as the sound of a radio, television or a noisy bar can make it difficult to impossible to understand speech, since spoken words may sound distorted either into irrelevant words or words that do not exist, depending on the severity of the auditory processing disorder. using a telephone can be problematic for someone with auditory processing disorder, in comparison with someone with normal auditory processing, due to low quality audio, poor signal, intermittent sounds and the chopping of words. many who have auditory processing disorder subconsciously develop visual coping strategies, such as lip reading, reading body language, and eye contact, to compensate for their auditory deficit, and these coping strategies are not available when using a telephone. as noted above, the status of apd as a distinct disorder has been queried, especially by speech-language pathologists and psychologists, who note the overlap between clinical profiles of children diagnosed with apd and those with other forms of specific learning disability. many audiologists, however, would dispute that apd is just an alternative label for dyslexia, sli, or adhd, noting that although it often co-occurs with these conditions, it can be found in isolation.