Factors affecting children’s performance

Fatigue or lapses in sustained attention can increase the number of incorrect perceptual decisions

made, which then results in inaccurate threshold estimation per se during a psychophysical task.

Wightman & Allen (1992) used simulated data to demonstrate that general inattention during a

proportion of trials of an adaptive psychophysical task led to higher thresholds and a flatter

psychometric function. The results were comparable to the actual results found in child data,

providing strong support for the theory that sustained attention, or lack of it, is a large contributing

factor in accurate psychophysics. In further support of this argument, Oh et al. (2001)measured

children’s pure tone signal detection with and without maskers. They found that children

experienced an increase in masked threshold masking effect when the masker and target were

spatially separated in frequency. As this effect is not seen in adults, it indicates that children are

more easily distracted by a distractor tone that is presented at a spatially separated frequency

(Werner & Bargones, 1991). Oh et al. (2001) argue that this is an effect of informational masking as

opposed to energetic masking, and that children utilise a wider range of auditory filters when

processing signals amongst distracting sounds. Informational masking refers to masking that occurs

when the masker is changing or uncertain, and may form part of a tone-in-noise masker effect in

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In opposition to the inattention argument, some studies have shown that lapses in attention will not

have an effect large enough to justify the masked threshold differences witnessed between children

and adults (e. g. Schneider & Trehub, 1992; Viemeister & Schlauch, 1992; Werner & Bargones, 1992).

Wightman & Allen (1992) showed that an inattention rate of 30% will shift the psychometric function

by only 2-3dB, therefore indicating that inattention alone is not the sole cause for the size of

difference in adult and child thresholds.

Children appear to have shallower psychometric slopes than adults, and the reason for this remains

largely unknown (Buss et al., 2006). Buss et al. (2006) proposed the possibility of an internal noise

hypothesis, stating that children may have certain characteristics which lead to their poorer

performance than adults in discrimination tasks. The hypothesis indicates that these characteristics

are likely to be neurally-based, however the authors concede that there may be other behavioural

factors such as lack of motivation or change of strategy which may also lead to poorer performance

than adults. A later study showed Buss et al. (2009) testing this internal noise hypothesis using

psychometric functions, with the premise that greater internal noise will lead to a shallower

psychometric function slope in children. Their findings supported this prediction, with children

yielding significantly shallower psychometric functions than adults. However, the actual nature of

internal noise remains unclear.

6.1.3.2 Neural immaturity

Development of cortical responses co-occurring with growing efficiency in psychophysical

performance might lead to the conclusion that it is immaturity of auditory neural responses that

make it difficult for children to complete an auditory task reliably. Olsho et al. (1987) conclude that

immaturity of the auditory system could be the cause of frequency threshold differences between

adults and infants. However, this is only one factor that might contribute to children’s poor

performance in the auditory discrimination tasks. Other influences may consist of cognitive aspects

of development such as poorer memory, which has been shown to be important in adult

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task here requires some memory capability, as there is a need to compare one trial with another

consecutively.

Some authors argue that children’s poorer performance than adults in auditory discrimination tasks

is not due to sensory or cognitive factors but instead due to behavioural differences. For example

Werner & Marean (1996) showed that some much younger observers are able to complete the

psychophysical tasks satisfactorily, leading to the hypothesis that very early development of sensory

factors gives children the potential to perform adequately. Despite this, Buss et al. (2009) conclude

that children’s poorer performance is not due to fluctuations in attention or listening strategy, as their

findings indicate that the psychometric function remains stable over blocks of trials when comparing

interleaved adaptive paradigms. If the children had lost attention for a block of trials this would be

reflected in variance in the staircase trial performance.

As has been described, there are a number of reasons why children may perform more poorly in an

auditory psychophysical task than adults. The effect of errors in behavioural tasks is so detrimental to

accurate BMLD estimation that it would seem advantageous to create a scenario where the BMLD

can be measured without the need for any behavioural task. The M100 provides a potentially

suitable measure for this kind of percept. Measurement of the M100 provides its own challenges in

children, as the response does not fully develop to an adult level of maturity until the age of 14-16

years (Goodin et al., 1978). However, the M100 first appears around the age of 9 (Tonnquist-Uhlen

et al., 2003), so it should be possible to measure the BMLD using this response in the same way as

has been described for adults in the previous chapter.

6.1.4 Stimulus effects on the auditory response