Implicit expectations influence target detection in children and adults

Abstract

When a sound occurs at a predictable time, it gets processed more efficiently. Predictability of the temporal structure of acoustic inflow has been found to influence the P3b of event-related potentials in young adults, such that highly predictable compared to less predictable input leads to earlier P3b peak latencies. In our study, we wanted to investigate the influence of predictability on target processing indexed by the P3b in children (10-12 years old) and young adults. To do that, we used an oddball paradigm with two conditions of predictability (high and low). In the High-predictability condition, a high-pitched target tone occurred most of the time in the fifth position of a five-tone pattern (after four low-pitched non-target sounds), whereas in the Low-predictability condition, no such rule was implemented. The target tone occurred randomly following 2, 3, 4, 5, or 6 non-target tones. In both age groups, reaction time to predictable targets was faster than to non-predictable targets. Remarkably, this effect was largest in children. Consistent with the behavioral responses, the onset latency of the P3b response elicited by targets in both groups was earlier in the predictable than the unpredictable conditions. However, only the children had significantly earlier peak latency responses for predictable targets. Our results demonstrate that target stimulus predictability increases processing speed in children and adults even when predictability was only implicitly derived by the stimulus statistics. Children did have larger effects of predictability, seeming to benefit more from predictability for target detection.

Figure 1

Schematic of the Stimulus Paradigm: In the High-predictability condition (A) a five-tone pattern was presented in 80% of the trials (green colored boxes), patterns containing a different amount of standards occurred in only 20% of the trials (orange colored boxes). In the Low-predictability condition (B) all patterns had equal probability. The target stimulus was the higher frequency (988 Hz) tone (dark grey).

Figure 2

Behavioral data: Mean reaction times (RT), hit rates (HR), and false alarm rates (FAR) for children and adults in both predictability conditions. Error bars represent the standard error of the mean. Direct comparisons are shown for descriptive purposes: n.s. – not significant, ${}^{\mathrm{*}\mathrm{*}}-{\mathrm{p}}_{\mathrm{F}\mathrm{D}\mathrm{R}}<.01,{}^{\mathrm{*}\mathrm{*}\mathrm{*}}<{\mathrm{p}}_{\mathrm{F}\mathrm{D}\mathrm{R}}<.001$.

Figure 3

ERP data: Mean grand-averaged ERPs for targets (red) and standards (blue) at frontal (F3, Fz, F4), central (C3,Cz,C4), and parietal (P3, Pz, P4) electrode clusters for children and adults.

Figure 4

Difference waveforms and P3b latency analysis. (A) Difference waveforms at frontal (F3, Fz, F4) and parietal (P3, Pz, P4) electrode clusters that were used for the latency analysis. Highlighted in gray are the analysis time-windows for the MMN and P3b amplitude. Horizontal black lines on the bottom of each line plot indicate the latency analysis time-windows for MMN and P3b. Vertical lines show the RTs from the two predictability conditions. (B) Results of the P3b onset and peak latency analysis in both age groups and predictability conditions. Adults show a P3b onset difference and children show both an onset and a peak latency difference. The MMN showed no significant peak latency difference (data not shown). n.s. – not significant, ${}^{\mathrm{*}\mathrm{*}}-{\mathrm{p}}_{\mathrm{F}\mathrm{D}\mathrm{R}}<.01,{}^{\mathrm{*}\mathrm{*}\mathrm{*}}<{\mathrm{p}}_{\mathrm{F}\mathrm{D}\mathrm{R}}<.001$.

Figure 5

ERP component distributions: Scalp voltage potentials (SP) and scalp current densities (SCD) in both predictability conditions and age groups for the MMN and P3b. Isolines are drawn at 1 μV and 0.1 mA/m³ steps, respectively.