Fiabilidad del instrumento

The grand mean average waveform at analysed sites for responses to each Valence category for women and men during the single and dual

Table 2

The Sex-specific Mean Valence and Arousal Ratings of the Presented Image Categories as provided by the IAPS Collection and as Rated by Study Participants

Variable Condition IAPS Participants

Women Men Women Men F p ηp²

Valence Neutral 5.69 (.90) 5.55 (.75) 5.30 (.50) 5.23 (.48) .04 .84 .001 Pleasant 5.87 (1.19) 6.47 (1.30) 6.22 (.66) 6.15 (1.54) 2.28 .14 .057 Unpleasant 2.19 (.90) 3.03 (1.06) 2.30 (.93) 2.31 (.91) .01 .95 <.001 Arousal Neutral 3.50 (.86) 3.40 (.87) 2.86 (1.55) 1.98 (.89) .04 .84 .001 Pleasant 5.53 (.97) 5.74 (1.56) 5.24 (.86) 5.29 (1.77) 1.54 .22 .039 Unpleasant 6.65 (.60) 6.01 (.62) 5.05 (.88) 3.79 (.41) 4.08 .050 .097

Note. Standard Deviations in parentheses; Univariate ANOVA results reported for ‘participant’ data; IAPS = International Affective Picture System (Lang, Bradley, & Cuthbert, 2008)

Figure 2. Grand mean average waveform of valence categories for women and men during the a) single and b) dual conditions.

7.4.3.1. Early Processing: P1

A significant main effect of Valence was revealed for the P1 peak amplitude data, F(1.41, 53.50)=7.35, MSE=10.62, p=.004, ηp²=.162, which

demonstrated that P1 amplitude was significantly greater to the neutral stimuli relative to the pleasant (p=.008) and unpleasant (p=.002) stimuli, with no significant difference in P1 amplitude found between pleasant and unpleasant stimuli. No other significant main effects or interactions were observed for the P1 component.

7.4.3.2. Early Processing: N1

The N1 peak amplitude data revealed a trend towards a significant Sex × Valence interaction, F(1.98,38)=2.91, MSE=99.20, p=.06, ηp²=.071,

however, Sidak post-hoc tests showed no significant differences between women and men at any valence, or between any valence for women or men. No other significant main effects or interactions were found for N1 amplitude.

7.4.3.3. Mid-latency Processing: N2

The N2 peak amplitude data revealed a significant main effect of Valence, F(1.54, 58.34 )=40.47, MSE=19.28, p<.001, ηp²=.516, which showed

that N2 amplitude was significantly higher to neutral relative to pleasant and unpleasant stimuli, with unpleasant stimuli higher than pleasant stimuli (ps<.001). This Valence main effect was superseded by a significant higher order Sex × Valence interaction, F(1.54, 38)=4.56, MSE=321.85, p=.02, ηp²=.107 (see Figure 3). Sidak post-hoc tests by Sex showed no significant differences. However, sidak post-hoc tests by Valence demonstrated that N2 amplitude for women was significantly higher to neutral (p=.002) and

unpleasant (p=.001) compared with pleasant stimuli, with no significant difference between neutral and unpleasant stimuli observed. For men, N2 amplitude for neutral was significantly higher than both pleasant (p<.001) and unpleasant (p=.001), with N2 amplitude also shown to be significantly higher to unpleasant compared to pleasant stimuli (p=.002).

A significant Condition × Valence interaction, F(1.93, 73.45)=4.34,

MSE=6.81, p=.02, ηp²=.10, was also found. Sidak post-hoc tests by Condition

showed that N2 amplitude was significantly higher during the single emotion processing relative to dual-oddball condition for pleasant stimuli, with no significant differences across conditions revealed for neutral or unpleasant stimuli. Sidak post-hoc tests by Valence demonstrated that N2 amplitude was significantly higher to neutral (p<.001) and unpleasant (p=.001) compared with pleasant stimuli, with no significant difference between neutral and unpleasant stimuli during the single emotion processing condition. During the dual- oddball condition, N2 amplitude for neutral stimuli was significantly higher than both pleasant (p<.001) and unpleasant (p=.001) stimuli, with N2 amplitude also shown to be significantly higher to unpleasant compared to pleasant stimuli (p=.001). No other significant main effects or interactions were found for the N2 component, including no significant Sex × Condition × Valence interaction, and the results did not suggest an impact of sex

7.4.3.4. Late Processing: P3

A significant main effect of Sex, F(1, 38)=24.84, MSE=231.94,

p<.001, ηp²=.395, was found for P3 amplitude which showed women to have

significantly higher P3 amplitude relative to men. A significant Valence main effect was also found, F(1.98, 75.07)=115.38, MSE=11.96, p<.001, ηp²=.752,

demonstrating that P3 amplitude was significantly higher to the pleasant relative to unpleasant and neutral stimuli, with unpleasant stimuli shown to elicit greater P3 amplitude that neutral stimuli (ps<.001). This Valence main effect was modified by a significant Condition × Valence × Site interaction,

F(2.81, 38)=2.68, MSE=231.94, p=.05, ηp²=.066 (see Figure 4). Breakdown

analyses were conducted to investigate this three-way interaction.

A Condition × Valence repeated-measures ANOVA at each Site was conducted and a main effect of Valence was found at P3, F(1.98,

77.89)=104.14, MSE=4.10, p<.001, ηp²=.728, PZ, F(1.83, 71.47)=117.73,

MSE=6.16, p<.001, ηp²=.751, and P4, F(1.95, 76.12)=71.47, MSE=4.40,

p<.001, ηp²=.647, sites. Sidak post-hoc tests revealed that irrespective of task condition, P3 amplitude at P3, PZ, and P4 sites was significantly greater to pleasant compared with neutral and unpleasant stimuli, with unpleasant stimuli also shown to be significantly greater than neutral stimuli (ps<.01).

A Valence × Site repeated-measures ANOVA for each task condition showed a main effect of Valence for both the single, F(1.78, 69.34)=71.23,

MSE=11.21, p<.001, ηp²=.646, and dual, F(1.93, 75.28)=77.24, MSE=8.77,

p<.001, ηp²=.664, conditions which demonstrated that P3 amplitude was

with unpleasant stimuli significantly greater than neutral stimuli during both conditions (ps<.002).

Similarly, a Valence × Site interaction was revealed for both the single, F(3.55, 138.46)=16.78, MSE=.82, p<.001, ηp²=.301, and dual, F(2.53, 98.69)=5.74, MSE=2.0, p=.002, ηp²=.128, conditions. Sidak post-hoc tests by

Valence revealed that, irrespective of task condition, P3 amplitude at P3, PZ, and P4 sites was significantly greater to pleasant compared with neutral and unpleasant stimuli, with unpleasant stimuli also shown to be significantly greater than neutral stimuli at all sites except P4 during the dual condition (ps<.03). During both the single and dual conditions, sidak post-hoc tests by Site demonstrated that P3 amplitude to pleasant stimuli was significantly greater at PZ relative to P3 and P4 sites (ps<.03), whereas P3 amplitude to unpleasant stimuli was greater at PZ compared with P3 site during the single (p<.02) and dual (p<.05) conditions. No significant findings were

demonstrated by a Condition × Site repeated measures ANOVA at each Valence level. No further significant main effects or interactions were demonstrated for P3 amplitude.

7.4.3.5. Late Processing: LPP

The LPP mean amplitude data revealed a significant main effect of Sex, F(1, 38)=14.86, MSE=183.79, p<.001, ηp²=.281, indicating that women

had significantly LPP amplitude overall than men (p<.001). A significant Condition main effect, F(1, 38)=5.28, MSE=40.65, p=.03, ηp²=.122,

demonstrated showed LPP amplitude to be significantly greater during the dual as compared with single condition (p=.03). Further, a significant main effect of Valence, F(1.96, 74.35)=155.12, MSE=8.76, p<.001, ηp²=.803, showed that

LPP amplitude was significantly greater to both pleasant and unpleasant relative to neutral stimuli (ps<.001), with no significant difference between pleasant and unpleasant stimuli observed. However, these findings were qualified by a trend towards a significant Sex × Condition × Valence interaction, F(2, 38)=2.85, MSE=183.79, p=.06, ηp²=.07 (see Figure 5). To

investigate this three-way interaction, a series of breakdown analyses were conducted.

A Sex × Valence interaction at each level of Condition produced significant main effects of Sex showing LPP to be significantly higher for women compared to men during the single, F(1, 38)=7.64, MSE=44.32,

p=.009, ηp²=.17, and dual, F(1, 38)=19.33, MSE=30.49, p<.001, ηp²=.34,

conditions. Significant main effects of Valence were also found and showed that LPP amplitude was significantly higher to the pleasant and unpleasant relative to neutral stimuli during the single, F(1.78, 67.66)=94.46, MSE=2.97,

p<.001, ηp²=.71, and dual, F(1.85, 70.16)=101.27, MSE=2.11, p<.001, ηp²=.73, conditions. A significant Sex × Valence interaction, F(1.85, 1)=3.84,

Breakdown of this two-way interaction by Sex showed that women displayed significantly greater LPP amplitude than men to the pleasant (p=.001),

unpleasant (p=.001), and neutral (p<.001) stimuli whereas sidak post-hoc tests by Valence showed that LPP amplitude was significantly greater to pleasant and unpleasant compared to neutral stimuli for both women and men

(ps<.001).

A Condition × Valence interaction at each level of Sex revealed main effects of Valence for both women, F(1.87, 35.46)=60.69, MSE=3.4, p<.001, ηp²=.76, and men, F(1.98, 37.59)=99.70, MSE=2.57, p<.001, ηp²=.84, with

each showing LPP amplitude to be significantly higher to the pleasant and unpleasant compared with neutral stimuli (ps<.001). A main effect of Condition, F(1, 19)=4.85, MSE=16.42, p=.04, ηp²=.20, showing LPP

amplitude to be greater during the dual relative to single condition was also found for women (p=.04).

A Sex × Condition interaction at each level of Valence revealed significant main effects of Sex showing that LPP amplitude was significantly greater for women relative to men for the pleasant, F(1, 38)=10.98,

MSE=22.70, p=.02, ηp²=.22, neutral, F(1, 38)=19.91, MSE=18.29, p<.001, ηp²=.34, and unpleasant, F(1, 38)=11.64, MSE=25.99, p=.02, ηp²=.24, stimuli.

Significant main effects of Condition were demonstrated for the pleasant, F(1, 38)=5.64, MSE=6.12, p=.02, ηp²=.13, and neutral, F(1, 38)=6.99, MSE=5.71,

p=.01, ηp²=.16, stimuli with each indicating that LPP amplitude was

significantly higher during the dual relative to single conditions. A trend towards a significant Sex × Condition interaction was also found for neutral stimuli, F(1, 38)=3.92, MSE=5.71, p=.055, ηp²=.093. Sidak post-hoc tests by

Sex showed that women had significantly higher LPP amplitude than men during both the single (p=.009) and dual (p<.001) conditions, whereas post-hoc tests by Condition demonstrated that LPP amplitude was significantly greater during the dual relative to single condition for women (p=.002). No other main effects or interactions reached significance for the LPP component.

Figure 5. The Sex × Condition × Valence interaction for LPP amplitude at P3, PZ, and P4 sites during the a) single and b) dual conditions.