This video provides a brief overview of the fundamental principles and concepts involved in performing visual reinforcement audiometry. You can find the full transcript below.
Visual reinforcement audiometry (VRA) is – as the word audiometry suggests – a method of performing a hearing test. VRA is typically used to test the hearing of infants and young children and can be effective in those as young as six months of age as this is the approximate age when an infant develops the neck strength and control required for the test.
VRA is generally used in children up to the age of approximately two and a half years but can also be useful in older children with complex needs and developmental delay. VRA involves the child looking towards a visual target such as a toy or an image on a screen in response to a sound stimulus. If using a toy, it should be screened from view of the child by smoked Perspex with the option to illuminate it when required to become visible.
An important aspect of VRA is the reinforcement element as the child sees the visual target each time they look towards it. But what exactly is being reinforced?
There are two main principles of VRA testing and it is these that are reinforced by the presentation of the visual target.
The VRA response is what is known as a conditioned response. This means that the child associates the presentation of the sound stimulus with a reward. In this case, the visual target, which they receive upon performing a head turn towards that target. This concept of conditioning is the first principle.
The second principle of VRA is that we must see that head turn towards the visual target. In some cases, you will hear this visual target described as a visual reward. But in fact, it is a visual reinforcer because it serves the purpose of reinforcing the conditioned head‑turn response throughout testing.
Successful conditioning of the child is essential for VRA testing to be effective and is the starting point for testing. The conditioning phase involves presenting both the sound stimulus at a suitably audible level and the visual reinforcer at the same time to condition the child that there is an association between the two.
During conditioning, the second tester should assist in encouraging the child to look towards the visual reinforcer and this should involve an appropriate level of social reinforcement such as:
It is often useful for the second tester to move towards the visual reinforcer to guide the child's attention towards it.
To check that conditioning has been successful, the sound stimulus should be presented on its own. If the child performs an independent head turn towards the visual reinforcer, the reinforcer should then be displayed. If the child doesn't turn after a second or two, the reinforcer should be displayed as part of ongoing conditioning with appropriate involvement from the second tester.
Successful conditioning is determined by at least two independent head turns towards the visual reinforcer in response to the sound stimulus alone. Once successful conditioning has been established, the testing phase can begin.
It may be necessary to recondition the child during testing if it appears that they have lost the association between the sound stimulus and the visual reinforcer. But care and skill are required in assessing whether this is due to loss of conditioning or whether it may be due to the sound being below the child's threshold and therefore inaudible.
In some cases, the conditioning phase may not be required. Presenting the first sound stimulus for a second or two without the visual reinforcer can sometimes elicit a spontaneous head turn. In this case, it is still important to establish those two independent head‑turn responses before proceeding with the testing phase.
There are four main considerations for VRA testing.
To maximize the time available – which is often limited due to the short attention span of infants – a 20 dB down, 10 dB up testing method is typically adopted. Smaller steps are recommended around the minimum response level. However, it is important to weigh up the benefits of measuring in smaller steps against time limitations and the need for testing at further frequencies or using other transducers.
A clear, time‑locked head turn should be used as the response. Responses or lack of responses should all be recorded using ticks and crosses on a VRA tick sheet.
Visual reinforcers should be displayed as soon as the child has produced a head turn. It is advisable to maintain the sound stimulus presentation for the same duration as the reinforcer is displayed to help maintain conditioning.
The second tester should have a varied selection of age-appropriate toys to engage the child's attention forwards throughout testing.
See also: Preparation and Setup for VRA Testing
The criterion for a minimum response level is defined by the British Society of Audiology as the lowest level at which a response occurs in at least two out of three ascending trials. That is: greater than fifty percent of the time.
In determining whether a response has been given, it is important to be aware of false positives or checking. A false positive response occurs when the child checks to look for the visual reinforcer regardless of sound stimulus presentation.
If a checking response coincides with the presentation of the stimulus, it can be mistaken for a true positive response. ‘No‑sound’ trials can be used to help ascertain to what extent the child is checking and an increase in the level of engagement with the second tester can help to reduce the amount of checking.
To summarize briefly, VRA is a behavioral test of hearing best suited for infants from six months to around two and a half years of age. VRA relies on the principles of conditioning and the child's head turn in response to the presentation of a sound stimulus.
Visual reinforcers are used as part of the conditioning phase and as a reward and ongoing reinforcement throughout testing. The aim of VRA is to identify minimum response levels at different frequencies to obtain information regarding the child's hearing.