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Objective: We examined the effects of several display characteristics of head-mounted displays (HMDs) on simulator sickness (SS). Background: Technological limitations, such as display delay and reduced field of view (FOV), affect perception when using an HMD and are often thought to be related to SS. Few studies have examined the relationship between FOV and geometric FOV (image scale factor) or how HMD characteristics may interact. Method: Participants made active head movements to locate objects when viewing a live video via an HMD. Results: Compared with no added delay, an additional 200 ms of display delay did not result in increased SS, as measured by the Simulator Sickness Questionnaire. Furthermore, an effect of image scale factor on SS was not revealed. However, SS was greater when peripheral vision was occluded than when it was not. Peripheral vision moderated the effects of image scale factor and delay on head movement velocity. Conclusion: Occluding peripheral vision may subject HMD users to the potential detrimental consequences of HMD characteristics more than when peripheral vision of the external environment is available, resulting in more SS. Future research should investigate to what extent peripheral vision can be occluded without increasing SS and without sacrificing realism and presence. Application: To reduce the occurrence of SS, a degree of peripheral vision of the external world should be provided. Furthermore, users and designers should be aware that head movement behavior may be affected by HMD characteristics.

In the Brown et al. study 'Increased food supply mitigates ocean acidification effects on calcification but exacerbates effects on growth' they show disagreement with the tested hypothesis and data analysis methodology used in our 2016 study. We acknowledge careful criticism and a constructive dialogue are necessary to progress science and address these issues in this reply. ; This work was funded by ASSEMBLE grant agreement No. 227799 from European Community and from the Spanish Ministry of Economy and Competitiveness (ESTRESX, number CTM2012-32603). L.R. acknowledges support from grant FONDECYT 3170156. L.R. and N.L. acknowledge support from grant NC 1200286 (Millennium Nucleus Project MUSELS) and PIA CONICYT ANILLOS ACT172037. I.E.H. was supported by Ramon y Cajal Fellowship RYC2014-14970, cofunded by the Conselleria d'Innovació, Recerca i Turisme of the Balearic Government (Pla de ciència, tecnologia, innovació i emprenedoria 2013-2017) and the Spanish Ministry of Economy, Industry and Competitiveness.

The impact of preceding questions on the reporting of legal blindness & other sight problems by those filling out surveys is examined, using data from the 1994 & 1995 National Health Interview Surveys & Disability Supplement (N = 1,590 respondents [Rs]). Rs who had been asked a preceding question about whether they had "serious difficulty seeing," a somewhat ambiguous phrase, were less likely to report sight difficulties than Ss asked this question later in the survey. How this phenomenon affects national estimates of serious difficulty seeing & legal blindness is considered, & further research confirming such context effects is presented. It is concluded that information on difficulty seeing & legal blindness may have been unintentionally biased by this & similar preceding questions. 29 References. D. Weibel