Sex differences in orienting to pictures with and without humans: evidence from the cardiac evoked response (ECR) and the cortical long latency parietal positivity (LPP)

Abstract

Objective: This study investigated the effect of social relevance in affective pictures on two orienting responses, i.e. the evoked cardiac response (ECR), and a long latency cortical evoked potential (LPP) and whether this effect would differ between males and females. Assuming that orienting to affective social information is fundamental to experiencing affective empathy, associations between self-report measures of empathy and the two orienting responses were investigated.

Method: ECRs were obtained from 34 female and 30 male students, and LPPs from 25 female and 27 male students viewing 414 pictures from the International Affective Picture System. Pictures portrayed pleasant, unpleasant and neutral scenes with and without humans.

Results: Both the ECR and LPP showed the largest response to pictures with humans in unpleasant situations. For both measures, the responses to pictures with humans correlated with self-report measures of empathy. While we found a greater male than female responsiveness to the pictures without humans in the ECR, a greater female than male responsiveness was observed in the LPP response to pictures with humans.

Conclusion and significance: The sensitivity of these orienting responses to social relevance and their differential contribution to the prediction of individual differences underline the validity of their combined use in clinical studies investigating individuals with social disabilities.

Figure 1. Topographical maps of the difference waves of ERPs in response to pictures with and without humans independent of valence (most left), neutral pictures with humans minus neutral pictures without humans, positive pictures with humans minus positive pictures without humans, and negative pictures with humans minus negative pictures without humans (most right).

Figure 2. Baseline-adjusted IBIs (in milliseconds) in response to the IAPS pictures (t = 0 s).

Left panel: pictures with humans present; right panel: pictures without humans.

Figure 3. Means and SEMs of the baseline-adjusted maximal IBIs (in milliseconds) illustrating the Human by Valence effect.

Note that these maxima are not completely equal to those of the deceleration curves as IBI_max is based on the individuals’ maxima, which may differ in delay.

Figure 4. Baseline-adjusted IBIs in response to the IAPS pictures (t = 0 s) separated per sex.

Upper panel: humans present in the pictures; lower panel humans absent.

Figure 5. Means and SEMs of the baseline-adjusted maximal IBIs illustrating the sex differential Human effect.

Figure 6. ERPs in response to pictures with and without humans illustrating the Human (P3) and Human*Valence interaction (P7) effects of the LPP in the time window of 550 to 700 ms.

Figure 7. ERPs of parietal electrodes (P3 and P7) depicting the Human*Sex and the Valence*Sex interaction.

Below the ERPs showing the grand averages for pictures with and without humans collapsed for valence (A) and for pictures with the different valences collapsed for human presence (B). The corresponding line graphs with mean amplitudes (and SEMs) of the 550 to 700 ms interval illustrate the interactions found.

Figure 8. Means and SEMs of the LPP values (average amplitudesof the 550 to 700 ms interval) at P7 (a) and the baseline-adjusted maximal IBIs (b) illustrating the sex differential Human effects.

Figure 9. Scatter plots for the correlations between (A) the Human effect on the LPP at P3 and the Personal Distress scale of the IRI for the males only, (B) the Human effect on the baseline-adjusted maximal IBI’s and the discrepancy between systemizing and empathizing behavior (D_SQ-EQ) for all participants, and (C) the Human effect on the LPP at P3 and the D_SQ-EQ for the females only.