the way in which individuals respond to daily stressors is a determinant of reactivity of the sympathetic - adrenal - medullary ( sam ) and hypothalamic - pituitary - adrenal ( hpa ) axes and contributes to allostatic load . in order to fully understand the reactivity of these axes it is necessary to observe individuals while they are experiencing stress .
naturalistic stressors provide ecologically valid measurement opportunities ; however they can be expensive and lack control and standardisation . alternatively
, laboratory stressors allow for the controlled manipulation of stimuli and more specific assessment of the causal factors involved in psychobiological stress responding . a variety of laboratory stressors comprising cognitive challenge , public speaking
, emotion induction and interpersonal stress are used for this purpose ; however , these tasks typically serve no function outside of the laboratory ( chida and hamer , 2008 ) . to obtain a comprehensive snapshot of how an individual would respond to a stressor encountered in a real - life setting , laboratory stressors should have ecological validity and be representative of experiences in natural settings . such settings rarely involve exposure to a single stressor as modelled in the laboratory , but instead individuals typically deal with multiple sources of stress ( chida and hamer , 2008 ) .
ecologically valid stressors should therefore comprise multiple stimuli and be representative of the types of situations encountered in everyday life .
the multitasking framework ( wetherell and sidgreaves , 2005 ) comprises eight individual cognitive tasks and elicits stress via the manipulation of workload intensity by increasing the difficulty and number of tasks ( up to a maximum of four during one presentation ) that a user must attend and respond to .
although the multitasking framework does not simulate a specific environment , it comprises tasks that are required in many working environments , such as calculations , continuous visual and auditory monitoring , and relevant stimuli identification .
moreover , as successful performance requires sustained effort , repeated multitasking does not lead to habituation of responding ( wetherell et  al . ,
several studies have demonstrated the efficacy of the multitasking framework as an acute stressor as evidenced by increases in stress , anxiety and fatigue ( e.g. , haskell et  al .
, 2010 , johnson et  al . , 2011 , wetherell and carter , 2013 ) ; cardiovascular reactivity ( e.g. , kelly - hughes et  al . , 2014 ) ; and mucosal immunity ( e.g. , wetherell and sidgreaves , 2005 ) .
only one study ; however , has reported an increase in cortisol reactivity following multitasking ( scholey et  al . , 2009 ) .
compared with sam responding , the hpa axis has a particularly high threshold for activation and acute increases in cortisol are typically observed in conditions of perceived uncontrollability involving motivated performance tasks accompanied by social evaluative threat ( i.e. threats to a valued aspect of self - identity or where the self is at risk of being negatively judged by others ; dickerson and kemeny , 2004 ) .
the multitasking framework is a motivated performance task and involves elements of uncontrollability ; but , it does not involve social evaluative threat , and cortisol reactivity would therefore not necessarily be predicted .
all of the conditions necessary for reliably inducing a cortisol response are , however , present in other laboratory stressors notably , the trier social stress test ( tsst ) , which involves a preparation period followed by the presentation of free speech and mental arithmetic to a socially evaluative panel whilst being recorded .
this paradigm is associated with robust increases in cortisol and has become a standard protocol for stress induction in healthy ( e.g. , kirschbaum et  al . , 1993 , kirschbaum et  al . , 1995 ) and clinical ( e.g. , buske - kirschbaum and hellhammer , 2003 ) populations of all ages ( e.g. , kudielka et  al . , 2004 , jessop and turner - cobb , 2008 ) .
there is , however , a need to develop alternative stress protocols that involve other sources of stress and are appropriate for repeated testing ( kudielka and wust , 2010 ) . in natural settings ,
exposure to social evaluation is omnipresent ; for example , giving presentations and being monitored during the performance of tasks in the workplace are commonplace and involve perceived threats to ones abilities , competencies or traits ( gruenewald et  al . , 2004 ) . a laboratory paradigm that is additionally representative of these settings
, cognitive multitasking is analogous to a range of environments requiring attendance and response to multiple stimuli and is associated with cardiovascular and psychological stress reactivity . given that critical social evaluation typically elicits hpa activation , the combination of multitasking and critical evaluation could therefore provide an easily administered acute stressor paradigm representative of everyday stressful situations .
the aim of the current study is , therefore , to assess whether a critically evaluated multitasking paradigm elicits activation of psychological , cardiovascular and hpa reactivity .
all recruitment and study procedures were granted ethical approval from the faculty ethics committee in line with the regulations of the institution and relevant regulatory bodies .
a total of 50 healthy participants ( range 1838 , mage  =  19.6 , sd  =  2.83 ; females  =  34 , males  =  16 ) were recruited from an undergraduate population and randomly allocated to either multitasking only ( mage  =  19.89 , sd  =  3.93 ; female  =  17 , male  =  8) or multitasking with critical evaluation ( mage  =  19.32 , sd  =  0.85 ; female  =  17 , male  =  8) .
eligibility criteria included : aged 1840 ; resting blood pressure less than 140/90  mmhg ; not pregnant or breastfeeding ; no self - reported anxiety or stress - related disorder . in addition , data were recorded for a number of factors that can alter hpa function ; specifically , body mass index ( bmi ) ; use of the contraceptive pill ( n  =  21 ) ; menstrual cycle stage ( first half  =  8 ; second half  =  14 ) ; and smoking status ( n  =  6 ) were also recorded as appropriate . the multitasking framework ( purple research solutions , uk ) is a platform for the presentation of performance - driven , cognitively demanding tasks and is analogous to working environments that require attendance and response to simultaneous stimuli .
this study used four tasks : auditory monitoring , visual monitoring , number entry , and memory search .
all tasks are points drive with points awarded for correct responses and points deducted for missed or incorrect responses .
participants are instructed to be as fast and accurate on all of the tasks as possible in order to achieve as high a score as they can .
the running total score is displayed in the middles of the screen whilst the tasks are running .
a full description of the framework is provided in wetherell and carter ( 2013 ) .
the ( 10 item ) perceived stress scale ( pss-10 : cohen et  al . , 1983 ) measured how often in the last month participants felt that life was unpredictable , uncontrollable , and overwhelming .
the 16 item bond - lader visual analogue scales ( bond and lader , 1974 ) measured the mood states of alert , content , and calm .
the nasa - tlx ( hart and staveland ( 1988 ) assessed mental , physical and temporal demand , effort , performance and frustration .
participants were asked to refrain from eating or drinking ( other than water ) for 1  h preceding the study .
all samples were frozen ( 20  c ) and assayed using the enzyme - linked immunosorbant assay method ( salimetrics - europe , uk ; intra and inter - assay coefficients < 10% ) .
table  1verbal prompts during critically evaluated multitasking.table  1time pointevaluative commentstressorcommencementwhen you click start , all of the tasks start at the same time.it is up to you how you spend your time , but you must be as fast & accurateon all of the tasks as you can in order to achieve as high a score as you can+4  minremember , you must be as fast & accurate on all of the tasks as you can+8  minyour score is on the low side , you should speed up+10  mini am now going to take your blood pressure , please continue with the tasks+12  minyou should be working faster than this+16  minyour score is still below the average+18  minyou only have 2  min remaining and you must get as high a score as you can20  mini am now going to take your blood pressure verbal prompts during critically evaluated multitasking .
mood , cardiovascular parameters and cortisol were assessed using mixed anovas with group ( multitasking , critically evaluated multitasking ) , time ( mood : pre , post ; cardiovascular : pre , mid , post ; cortisol : pre , post , post+10 , post+20 ) , and sex ( male , female ) .
there were no significant between group differences in age , bmi , sex or levels of perceived stress and no significant effects of pill use , menstrual cycle stage or smoking status on cortisol reactivity in either condition .
there were no significant sex x group or time interactions for any of the study variables .
table  2mean ( s.d ) values for physiological indices.table  2multitaskingn  =  25critically evaluated multitaskingn  =  25cardiovascular  heart rate  ( bpm)premidend77.2 ( 13.7)77.3 ( 10.3)75.4 ( 8.9)79.3 ( 9.8)83.8 ( 8.3)79.9 ( 7.3 )  systolic blood pressure  ( mm hg)premidend119.5 ( 12.8)117.2 ( 13.5)116.5 ( 11.5)117.2 ( 12.2)119.2 ( 13.1)118.7 ( 13.5 )  diastolic blood pressure  ( mm hg)premidend74.1 ( 10.1)73.6 ( 8.1)71.0 ( 8.7)72.4 ( 10.3)74.3 ( 8.7)72.6 ( 9.3)cortisol(nmol / l)prepost+10min+20min11.5 ( 8.3)8.8 ( 5.4)6.7 ( 6.3)6.3 ( 4.0)10.8 ( 5.7)9.5 ( 7.1)7.1 ( 3.6)6.7 ( 3.5)bpm  =  beats per minute ; mm hg  =  millimetres of mercury ; nmol / l  =  nanomoles per litre
bpm  =  beats per minute ; mm hg  =  millimetres of mercury ; nmol / l  =  nanomoles per litre .
a post - stress increase was observed in anxiety ( f(1,48 )  =  9.85 , p  =  0.003 ,   =  0.17 ) and post - stress reductions were observed for calmness ( f(1 , 48 )  =  66.63 , p  =  <  0.001 ,   =  0.581 ) , contentment ( f(1,48 )  =  24.259 , p  = < 0.001 ,   =  0.336 ) , and happiness ( f(1,48 )  =  8.2 , p  =  0.006 ,   =  0.146 ) .
significant group x time interactions were observed for anxiety ( f(1,48 )  =  4.9 , p  =  0.032 ,   =  0.09 ) , calmness ( f(1,48 )  =  13.56 , p  < 
0.001 ,   =  0.22 ) , contentment ( f(1,48 )  =  4.9 , p  =  0.03 ,   =  0.09 ) , and happy ( f(1,48 )  =  9.14 , p  =  0.004 ,   =  0.16 ) . bonferroni corrected t - tests revealed significantly greater post - stress levels of anxiety ( p  =  0.026 ) and lower levels of contentment ( p  =  0.05 ) and calm ( p  =  0.01 ) following critically evaluated multitasking compared with multitasking alone .
critically evaluated multitasking led to significantly greater levels of mental ( t(48 )  =  2.742 , p  =  0.009 ) ; physical ( t(48 )  =  2.073 , p  =  0.044 ) ; and temporal demand ( t(48 )  =  2.137 , p  =  0.038 ) ; effort ( t(48 )  =  2.508 , p  =  0.016 ) ; frustration ( t(48 )  =  5.000 , p  = <
0.001 ) and reduced perceived performance ( t(48 )  =  2.597 , p 
table  3mean ( s.d ) values for psychological indices.table  3multitaskingn  =  25critically evaluated multitaskingn  =  25perceived stress16.8 ( 4.2)17.4 ( 3.7)mood ( mm )  alertpre60.6 ( 10.1)61.6 ( 16.4)post58.8 ( 14.6)55.1 ( 16.5 )  contentpre71.8 ( 9.3)71.6 ( 12.1)post66.5 ( 10.8)57.7 ( 16.0 )  calmpre64.1 ( 14.5)68.1 ( 15.3)post52.9 ( 17.8)38.6 ( 16.5 )  anxiouspre29.6 ( 20.8)31.8 ( 22.2)post32.1 ( 17.7)46.3 ( 21.2 )  happypre63.2 ( 16.6)70.6 ( 16.9)post63.7 ( 18.8)52.9 ( 19.6)perceived workload ( mm )  mental demand * * 55.0 ( 24.4)71.8 ( 18.6 )  physical demand*20.9 ( 17.3)32.9 ( 23.2 )  temporal demand * 56.2 ( 22.9)68.8 ( 18.4 )  effort * 55.4 ( 22.3)70.9 ( 21.5 )  perceived performance * 65.3 ( 20.9)51.2 ( 17.3 )  frustration * * 32.5 ( 16.0)60.8 ( 23.3)mm  =  millimetres.between group differences : * p  <  0.05 ; * * p  <  0.001 .
mean ( s.d ) values for psychological indices . between group differences : * p  <  0.05 ; * * p  <  0.001 .
significant main effects of time were observed for heart rate ( f(2,47 )  =  5.42 , p  =  0.009 ,   =  0.182 ) , and diastolic blood pressure ( f(2,47 ) 
=  4.27 , p  =  0.020 ,   =  0.154 ) .
a significant group x time interaction was observed for systolic blood pressure ( f(2,47 )  =  3.71 , p  =  0.032 ,   =  0.136 ) .
a significant reduction in cortisol was observed across the stressor period ( f(3,46 )  =  37.6 , p  <  0.001 ,   =  0.71 ) .
there were no between group differences or time x group interaction ( p  >  0.05 ) .
the current study assessed psychological , cardiovascular and hpa reactivity in response to critically evaluated multitasking and multitasking alone . multitasking led to increased psychobiological reactivity ; specifically increases in heart rate , diastolic blood pressure , and anxiety and reductions in positive mood states of calmness , contentment and happiness .
critically evaluated multitasking increased systolic blood pressure and anxiety , reduced contentment and calmness and led to greater perceived workload on all domains , over and above that observed following multitasking alone .
numerous studies ( cf dickerson and kemeny , 2004 ) have demonstrated that critical social evaluation elicits robust increases in cortisol , and alongside the other key stressor components of cognitive challenge and uncontrollability , forms an integral part of laboratory stressors such as the tsst . in this study , however , critically evaluated multitasking did not elicit a cortisol response .
the reduction in cortisol observed during the stressor period is likely indicative of the decline associated with the typical diurnal decline of cortisol .
physiological processes respond to meet the demands of the environment and terminate that response once the demands are met ( gunnar et  al . , 2000 ) . furthermore , unlike the sam axis , the hpa axis has a particularly high threshold for activation , and subsequently has longer - lasting effects ( shirtcliff et  al . , 2012 ) .
if the threat associated with a situation is perceived to be low , this will be reflected in the subsequent physiological responses .
a situation of low perceived threat may , therefore , involve only brief withdrawal of parasympathetic inhibition or a brief rise in cardiovascular activity to activate the sam - mediated fight - or - flight response .
this may account for the observed profile of responding in the current paradigm , that is , cardiovascular responding indicative of activation of the fight - or - flight response , but insufficient perceived threat to activate the hpa axis , despite increased reports of anxiety and demand .
an absence of cortisol responding has also been observed in other paradigms involving challenging situations in the presence of others .
paradigms that incorporate friendly or inattentive rather than socially evaluative panels do not elicit cortisol reactivity ( wiemers et  al .
, 2013 , dickerson et  al . , 2008 ) , suggesting that the provision of critical social evaluation , rather than just the presence of others is necessary for hpa activation .
the current paradigm incorporated a record of participation ( video recording of participant ) and critical evaluation of performance , and was perceived as demanding and anxiety provoking ; however , it may not have been perceived as a threat to self .
perception of social evaluation was not explicitly measured in this study ; however , the absence of cortisol responding , in an otherwise stressful and demanding paradigm , does suggest a missing stress eliciting component .
that is , whilst the current manipulation comprises challenge and critique , it may lack the socially evaluative element that has been previously associated with hpa activation in other paradigms .
this may be evidenced by notable differences between the current paradigm and the tsst , which is associated with robust cortisol responding .
both paradigms incorporate a motivated performance task and the presence of critical evaluation ; however , they differ in terms of the required response format of the performance task ; and the position of the participant in relation to the evaluator .
the tsst requires the participant to verbally perform a free speech task followed by a verbal mental arithmetic task ; in contrast the multitasking framework requires responses via a computer with no verbal component .
public speaking is a significant stressor involving the risk of embarrassment and humiliation ( garcia - leal et  al . , 2014 ) ,
and as such , the requirement to verbalise responses may represent the salient challenge to self that is necessary for hpa activation .
cold pressor , a passive coping task typically associated with minimal hpa activity , leads to significant increases in cortisol when accompanied with social evaluation .
specifically , a standard cold pressor procedure whilst being video recorded and evaluated by an experimenter leads to significant increases in cortisol in participants tested alone ( schwabe et  al . ,
2008 ) and in groups ( minkley et  al . , 2014 ) , suggesting that social evaluation may represent a salient threat even in the absence of a critique of a motivated performance task or a verbal component .
the remaining notable distinction between this paradigm and the tsst relates to the nature of social evaluation .
evaluation in the tsst and socially evaluated cold pressor involves being directly observed by an evaluator , and in the case of the tsst involves standing directly in front of a panel .
direct social evaluation , even in the absence of critique leads to increased perceived vulnerability and cortisol increases are therefore likely in situations where there is a threat to self - presentation and a greater risk of negative evaluation ( schwabe et  al . , 2008 ) .
although the current paradigm involved the observation and critique of performance , and therefore a potential challenge to one 's self , this challenge was indirect .
the participant was therefore able to avoid direct evaluation and focus on the tasks , as evidenced by increases in psychological and cardiovascular responding typical of motivated performance tasks .
first , although the sample is small , it was sufficient to observe meaningful differences in variables of interest in line with previous studies that have used the framework ( e.g. , wetherell and carter , 2013 ) .
second , sex differences can impact upon acute stress responding , in particular reactivity of the hpa axis with males typically demonstrating greater reactivity than females ( kudielka et  al .
although attempts were made to ensure balanced numbers of males and females across conditions , the current sample comprised a greater number of females than males .
there were no observed sex differences for any of the psychological or physiological variables ; however , future studies should use this paradigm in larger , more balanced samples . notwithstanding these limitations
, the current paradigm affords several advantages and opportunities for stress testing . from a methodological perspective , in response to the call for the development of alternative stress testing protocols ( kudielka and wust , 2010 ) ; the multitasking framework provides an ecologically valid technique for eliciting psychobiological reactivity ; it is appropriate for repeated testing ; and it comprises inherent measures of performance ( scholey et  al . , 2009 ) .
in addition , critically evaluated multitasking offers a paradigm representative of everyday situations requiring attention to multiple stimuli whilst being monitored and evaluated . as the paradigm requires minimal physical and human resource it therefore offers an alternative , economical laboratory stressor .
the paradigm can also be used to address a number of research questions relating to the role of social evaluation .
the current study reported the effects of additional critical evaluation on psychobiological indices and perceptions of stress and demand ; however , future studies could utilise the inherent performance measures to ascertain the impact of critical evaluation on actual task performance , thus providing a useful tool for modelling work - based performance during evaluation .
the absence of cortisol reactivity following critically evaluated multitasking also presents a number of opportunities for assessing the salient social components that are associated with hpa activation in other paradigms .
that is , it appears that the levels of interpersonal threat experienced in the tsst are not present in the current paradigm .
further manipulations regarding the nature of the critical evaluation received in addition to multitasking , for example , face - to face , rather than over - the - shoulder critical evaluation , or the requirement for verbal responding , would allow for a greater understanding of the role of interpersonal threat in relation to hpa activation . in conclusion ,
the increases in perceived workload , anxiety and cardiovascular responding following multitasking with critical evaluation demonstrate the stress - inducing effects of this protocol .
the current paradigm is an easily administered laboratory analogue of everyday situations involving the performance of multiple tasks whilst being critically evaluated , and therefore provides an ecologically valid paradigm for the assessment of psychological and cardiovascular stress responding .
the absence of cortisol reactivity , however , suggests some added subtlety in the factors that elicit hpa responding , that is , not all critically evaluated situations are perceived as a significant threat to self , and direct observation is likely to provide the additional social evaluation that is associated with hpa activation .
future developments of this paradigm could therefore assess the importance of in person , face - to - face contact to an evaluative other whilst maintaining the ecologically valid components of the paradigm .
 in order to understand psychobiological responses to stress it is necessary to observe how people react to controlled stressors . a range of stressors exist for this purpose ; however , laboratory stressors that are representative of real life situations provide more ecologically valid opportunities for assessing stress responding . 
 the current study assessed psychobiological responses to an ecologically valid laboratory stressor involving multitasking and critical evaluation . 
 the stressor elicited significant increases in psychological and cardiovascular stress reactivity ; however , no cortisol reactivity was observed . 
 other socially evaluative laboratory stressors that lead to cortisol reactivity typically require a participant to perform tasks that involve verbal responses , whilst standing in front of evaluative others . 
 the current protocol contained critical evaluation of cognitive performance ; however , this was delivered from behind a seated participant . 
 the salience of social evaluation may therefore be related to the response format of the task and the method of evaluation . 
 that is , the current protocol did not involve the additional vulnerability associated with in person , face - to - face contact , and verbal delivery . critical evaluation of multitasking provides an ecologically valid technique for inducing laboratory stress and provides an alternative tool for assessing psychological and cardiovascular reactivity . 
 future studies could additionally use this paradigm to investigate those components of social evaluation necessary for eliciting a cortisol response . 
Introduction
Method
Results
Discussion
Funding source