human nature is uniquely characterized by the flexibility , complexity , and sophistication with which thought and behavior can be deployed in the service of a goal . this ability is thought to depend on cognitive control , a collection of mechanisms , including perceptual selection , response biasing , and online maintenance of contextual or goal information , by which the human cognitive system adaptively configures itself to optimally perform specific tasks ( miller and cohen , 2001 ; braver et al . , 2002 ) .
most of the goals pursued in daily life are emotionally or motivationally meaningful  i.e. , to obtain outcomes that are pleasurable or important for survival , and avoid outcomes that are not .
it has long been understood that such affective significance is central to determining the goals around which human behavior is organized ; indeed , impairments in affectively driven goal - pursuit may be a critical component of a number of psychiatric disorders , such as depression and schizophrenia ( pessoa , 2008 ) .
consequently , the psychological and neurobiological mechanisms by which affective influences modulate cognitive control have become of major interest in recent years and continue to be an important emerging topic of study .
much of the experimental research examining how affect modulates cognitive control has involved one of two types of manipulations : emotional manipulations , in which affectively valenced subjective experience is directly induced ( e.g. , through mood inductions or exposure to emotional stimuli ) , or motivational manipulations , where motivational state is altered through the introduction of rewarding or punishing incentives .
both types of manipulations are thought to carry affective significance , and both have been hypothesized to impact goal - pursuit and/or cognitive control . however , for the most part , these bodies of research have been carried out independently of one another . in a recent review , pessoa aimed to ameliorate this situation by considering examples of both an emotional manipulation ( threat ) and a motivational manipulation ( reward ) on cognition within a common conceptual framework ( pessoa , 2009 ) .
his review suggests that both threat and reward operate in highly similar ways , impacting cognitive performance at both perceptual and executive stages of information processing .
however , pessoa acknowledges that emotion and motivation are broad constructs , the impacts of which may not be comprehensively characterized by the phenomena of threat and reward alone .
in contrast , and as described further below , other theories of emotion and motivation suggest the possibility of dissociations between the two constructs ( e.g. ,  liking  versus  wanting  ; berridge , 1996 ) but this remains an understudied issue .
thus , the goal of the present paper is to discuss more explicitly existing theoretical accounts regarding the relationship of emotion and motivation to cognitive control , examine how they may relate to one another , and speculate on commonalities and differences in the mechanisms by which they operate .
we also suggest future research directions that could be pursued to clarify ambiguity regarding the emotion versus motivation distinction .
emotion and motivation are highly related constructs within the domain of affect ( rolls , 2000 ; lang and bradley , 2008 ) , but their influences on cognition generally have not been explicitly considered in relation to one another . when examining the literature regarding the impact of each on cognitive performance , it is important to provide working definitions of relevant terms , so as to begin more carefully examining how these constructs may relate to one another .
one review suggests that emotions are best functionally defined as  psychological or physiological states that index occurrences of value  ( dolan , 2002 ) .
as this description suggests , emotion is generally conceptualized as a construct that can be decomposed into multiple subcomponents defining the relation between individual and environment .
davidson et al . ( 1990 ) suggest that emotions are comprised of three elements : autonomic reactions , cognitions , and behaviors .
more recently , roseman ( 2008 ) asserts that emotion can be thought of as a syndrome of phenomenology ( thought and feeling qualities ) , physiology ( neural , chemical , and other physical responses in the brain and body ) , expressions ( signs of emotion state ) , behaviors ( action tendencies or readinesses ) , and emotivations ( characteristic goals that people want to attain when the emotion is experienced ) .
gendron and barrett ( 2009 ) similarly claim that emotions are comprised of subprocesses , including an affective and cognitive ( e.g. , situational construal ) component , and are highly contextualized in nature .
common to all of these definitions is the idea that emotions are an affective experience that can be characterized by physiological changes and defined by a cognitive construal of some kind . as states indexing occurrences of value
, emotions have been proposed to carry functional value in physiologically preparing the body for action , permitting flexibility of behavioral responses to reinforcing stimuli , facilitating communication and social bonding , and influencing cognitive processes including evaluation , memory encoding , and memory recall ( rolls , 2000 ) .
motivations are similar to emotions in that they also serve to define the relation between the individual and the environment ( roseman , 2008 ) , but differ from emotions in being more tightly linked to action and explicit goal associations ; motivated action can be thought of as behavior that is at least partly determined by a desired and hedonically laden end - state ( i.e. , it is goal - directed ) .
pessoa ( 2009 ) suggests that motivation can be commonly defined as what makes one work to obtain reward or to avoid punishment .
similarly , roseman ( 2008 ) proposes that a motivation is an internal state producing behavior which moves the individual toward desirable reference values or away from undesirable reference values .
carver suggests a useful distinction between the two constructs as they relate to goals : while motivation may be the drive toward goal fulfillment , emotion may be emergent from one s sensed rate of progress toward goals ; the difference between one s present status and one s goal state is experienced as affect and may lead to goal reprioritization in order to maximize goal fulfillment ( carver , 2006 ) .
similarly , rolls ( 2000 ) suggests that emotions are states elicited by rewarding and punishing reinforcers of behavior .
likewise , lang and bradley ( 2008 ) claim appetitive and defense - related brain circuits have evolved to cope with motivationally significant stimuli in the environment ; positive and negative emotion , respectively , are associated with the experience of these brain circuits being activated . thus , according to this general view , emotion can be considered an emergent property of motivationally driven neural activity .
however , the lang and bradley view also suggests that emotion is highly characterized by hedonic experience , which accordingly is also tied to the activation of motivational neural circuitry .
which motivational system is activated by a stimulus event ( i.e. , appetitive or defensive ) 
buck ( 2000 ) and laming ( 2000 ) , commenting on d : rolls:2000 ] review of emotion and motivation , argue that emotion and motivation can not be considered separately of one another : laming ( 2000 ) argues that emotion is the subjective experience of being motivated , thus there is no separation between the two ; buck argues that motivation and emotion can not be distinguished from one another if emotion is , as he describes , the  manifestation or 
( buck , 2000 ) . a contrasting perspective can be drawn from the work of kent berridge , which has highlighted the potential dissociation between activation of motivational circuitry and the neural systems that code for hedonic experience ( berridge , 1996 , 2003 ; berridge and robinson , 1998 , 2003 ; berridge et al . , 2009 ) .
he proposes that the hedonic ( i.e. , subjective experiences of pleasure / displeasure ) and motivational ( i.e. , attribution of incentive salience ) facets of reward , shorthanded as  liking  and  wanting  respectively , are neurobiologically dissociable : evidence from rodents indicates that hedonic activation may depend on opioid - related circuitry while attribution of incentive salience may depend on the mesolimbic and neostriatal dopamine ( da ) systems .
this work suggests that the constructs of emotion and motivation might involve separable neural mechanisms , and as such may have distinct influences on cognitive processing .
however , roseman ( 2008 ) has recently suggested key differences : while both may lead to goal - directed action , he proposes several differences between emotion and motivation .
roseman argues that motivations are specific , relatively deliberate , and associated with a specific goal .
in contrast , emotions are produced by multiple contingencies , are somewhat more impulsive , and are not tightly linked to a particular goal .
additionally , he suggests that emotions typically take precedence over motivations : specifically , by engendering emotivations , emotion - specific motivations , that take precedence over non - emotional motivations .
these emotivations could potentially be understood ( in terms of carver s conceptualization of emotion ) as a manifestation of goal reprioritization resulting from emotion as an indicator of motivational status . from these working definitions and theoretical accounts of the relationship between emotion and motivation ,
we suggest that an emotion may be presently considered a construct of multiple processes that together serve to provide an index of value associated with an internal or externally experienced state .
while a motivation may be similarly comprised of multiple components , a motivation should be considered a state that produces behavior specifically oriented to carry out a goal that has hedonic value .
thus , whereas an emotion may emerge from one s status relative to motivational goals , it may not necessarily be directly relevant to a particular goal .
examining the influences of emotion and motivation on cognitive performance may be fundamental to clarifying the relation between these constructs ; currently , however , these investigations have been conducted largely in parallel .
the goal of this paper is to integrate these literatures by highlighting some key theoretical accounts of emotional and motivational influences on cognition , and illustrating where empirical evidence suggests these influences may diverge .
to facilitate comparison between the emotional and motivational literatures , we have chosen to restrict the focus to studies involving positive emotions and reward incentives .
it is , of course , also crucial to explore the relationship between negative emotions and punishment / avoidance - based motivational states , but as positive and negative emotion may be independent of one another ( watson et al . , 1988 ) , the extent to which they share the same mechanisms on cognition remains unclear .
gray and braver ( 2002 ) postulate that investigations of emotional influences on cognitive control should fulfill two global aims .
the first is to determine whether emotional influences can and do have a selective influence on cognitive control : this must be established first and independently of the nature of these influences .
the second aim is to elucidate the mechanisms by which such influences operate . in the present section ,
we discuss psychological theories regarding the adaptive value of positive emotion on cognition as well as theories regarding the specific mechanisms by which positive emotion takes its effect .
it has been suggested that positive emotion might be an adaptive signal indicating safety and security in the environment , giving the organism the freedom to explore and engage in new opportunities ( fredrickson , 2004 ) .
building on this postulation , several psychological theories have suggested that positive affect serves to broaden cognition , promote creative problem - solving , and improve cognitive flexibility .
foundational work in this area was conducted by isen and daubman ( 1984 ) , who observed that positive affect induction led to broader categorization and facilitated creative problem - solving ( isen et al . , 1987 ) .
relatedly , fredrickson ( 2004 ) proposed the broaden - and - build theory of positive emotions , which posits that positive emotions broaden one s repertoire of thought and action , promoting building of intellectual , social , and psychological resources . in the cognitive domain , empirical support for the broaden - and - build theory
has come from visual processing and semantic association tasks suggesting a broader scope of attention ( fredrickson and branigan , 2005 ) .
dovetailing nicely with this work is carver 's ( 2003 )  coasting hypothesis ,  which suggests that the security of positive affect might emerge from one s sensed rate of progress toward goals , and result from goal completion at a faster rate than anticipated . under such circumstances , one is free to 
coast  on the goal in question and consider new ideas and/or the pursuit of other goals ( leading to changes in goal prioritization ) .
one influential theory , the dopaminergic theory of positive affect ( ashby et al . , ( 1999 ) was developed to address findings that positive emotion is linked to broadened cognition .
ashby and colleagues extrapolated from the literature on the neural substrates of reward processing to propose that the psychological effects of positive emotion are specifically linked to increased dopamine ( da ) release ( via the substantia nigra and ventral tegmental area ) in these states .
the particular cognitive effects of increased da release during positive affect were postulated to occur through mesocorticolimbic system projections to the anterior cingulate cortex ( acc ) and substantia nigra projections to striatum , with increased da facilitating the ability of acc and striatum to initiate a switch among active task sets , rules , or goal representations maintained in lateral prefrontal cortex ( pfc ) .
this facilitation of switching among task - set representations under positive affect enables unusual or non - dominant sets to become active with a greater probability than under neutral affect conditions , which then facilitates creative problem - solving . in connectionist simulations ,
the account was tested and exhibited an ability to account for certain behavioral performance patterns observed by isen and colleagues under positive affect manipulations ( i.e. , improved performance on creative problem - solving and semantic association tasks ; ashby et al . , 1999 , 2002 ) .
dreisbach and goschke ( 2004 ) , dreisbach ( 2006 ) , and muller et al .
( 2007 ) developed a related theoretical framework , which emphasizes that the cognitive flexibility associated with positive affect may have systematic costs in addition to the benefits posited by broadening theories .
specifically , dreisbach proposed that changes in dopamine activity triggered by positive affect lead to a shift in the balance between cognitive stability and cognitive flexibility , by increasing the tendency to update to new task goal representations and decreasing the tendency to perseverate in maintaining old ones . empirical evidence from performance in set - shifting and context maintenance paradigms was consistent with this hypothesis ,
demonstrating positive affect induced facilitation of performance under conditions that depended on flexibility , but impairment under conditions stressing maintenance ( dreisbach and goschke , 2004 ; dreisbach , 2006 ) . a separate theoretical account , put forward by gray ( 2001 ) and gray and braver ( 2002 ) , argued for a hemispherically specialized basis of interactions between positive affect and cognitive control . in this account , an important congruence is noted between prior affective research associating positive emotions with increased activity in the left frontal cortex ( davidson et al . , 1990 ; davidson , 1992 ; davidson and irwin , 1999 ; canli et al . , 2001 ) , and cognitive research linking the left frontal cortex to the active maintenance of verbal information in working memory ( desposito et al . , 1998 ;
the primary theoretical claim of the account is that different affective states ( positive versus negative ) should trigger associated behavioral goals in working memory , and that it is adaptive for these goals to be hemispherically segregated such that they can be selectively prioritized by the appropriate affective state .
thus , the theory postulates that positive affect states should selectively facilitate verbal working memory  a hypothesis that was confirmed experimentally ( gray , 2001 ) . nevertheless , this account is agnostic about why positive and negative affect would be selectively linked with particular stimulus modalities in working memory . in summary ,
theoretical accounts of the effect of positive emotion on cognition have tended to emphasize influences on cognitive flexibility , potentially by enhancing updating of goal information in working memory . although most work has emphasized the adaptive value of such influences , it has also been suggested to come at a cost to goal maintenance . at the level of neural mechanisms
, the focus has been on the dopamine system and pfc , which , as is discussed next , has strong parallels to theoretical accounts regarding how motivation might modulate cognitive control .
theoretical accounts of motivation suggest a strong linkage to cognitive control ( simon , 1967 ; carver and scheier , 1998 ; kruglanski et al . , 2002 ) .
although early motivational theories suggested a general drive or energization function for motivation ( miller , 1951 ; hull , 1952 ; duffy , 1962 ) , information processing accounts of higher - level cognition have instead emphasized that motivational signals may play a more focused role in the prioritization , updating , and termination of goal representations that provide hierarchical control of behavior ( simon , 1967 ) . over the last 20  years , the intrinsic relationship between motivation and goals has been a central focus of researchers primarily working within the social and individual differences tradition , based on the central claim that motivations are expressed primarily as the activation and representation of specific cognitive and behavioral goals over others ( kruglanski et al . ,
more recent work has been geared toward demonstrating that goal - directed behavior can be primed and biased by implicit and/or subliminal motivational cues , suggesting a relatively direct route for motivation  cognition interactions ( bargh et al . , 2001 ; custers and aarts , 2010 ) .
( 2008b ) have suggested an affective / motivational account of goal - pursuit in which positive motivational signals strengthen goal activation and maintenance , even when this occurs outside of conscious awareness .
more recently , psychological theories postulating the role of motivation in activating goals and guiding behavior have begun to be bridged with neuroscience - based studies to more clearly specify the mechanisms by which motivation might influence cognitive control .
a primary focus of neuroscience studies on motivation and cognitive control has been to demonstrate that these two processes are integrated within specific brain regions , such as the lateral pfc .
early work involving single - unit recording in primates demonstrated that task - related neuronal activity in pfc was modulated by the expected reward value associated with performance ( watanabe , 1996 ; leon and shadlen , 1999 ; watanabe et al . , 2002 ) .
in one compelling demonstration , it was found that reward value directly enhanced the fidelity of active maintenance in working memory ( leon and shadlen , 1999 ) .
more recent fmri studies carried out in humans have used designs that orthogonally manipulate cognitive control demand and motivational value across a range of task domains , including working memory ( pochon et al . , 2002 ;
2004 ) , context processing ( locke and braver , 2008 ; kouneiher et al . , 2009 ) , task - switching ( savine and braver , 2010 ) , and selective attention ( padmala and pessoa , 2011 ) .
these studies have confirmed the presence of specific regions within lateral pfc ( along with effects in other associated regions , such as the acc ) that are sensitive to the interaction of the two factors , consistent with a specific role in integrating motivational and cognitive control functions .
the da system also plays a central role in accounts of both motivation and cognitive control .
dopamine has long been thought to be a critical component of motivation and reward processing ( wise and rompre , 1989 ; mirenowicz and schultz , 1996 ; robbins and everitt , 1996 ; schultz , 1998 ) .
more recent accounts have suggested that da shows phasic , cue - triggered responses to specific events that indicate reward availability ( montague et al . , 1996 ; schultz et al . , 1997 ) and/or high motivational salience ( berridge , 2007 ) .
this signal , particularly when a reward is different from anticipated ( i.e. , prediction error ) , may serve as a mechanism for reward - based associative learning ( schultz et al . , 1997 ; schultz , 2002 ; arias - carrion and poppel , 2007 ) .
while the role of dopamine as a learning versus salience signal in reward has been debated ( berridge , 2007 ) , both kinds of accounts are compatible with the idea of phasic da involvement in processing motivational incentives and thus consistent with our account .
additionally , a separate theoretical account has emphasized that the motivational utility of the current environmental context might be reflected in tonic , rather than phasic , da activation ( niv et al . , 2007 ) .
together , these accounts suggest da activity will be increased both by transient cues and sustained contexts that indicate high reward or motivational value . it is worth noting a completely separate literature focused on the influence of da release within pfc , which suggests that the da system provides modulatory role on cognitive control functions .
neurophysiological studies in primates show that application of da into pfc sharpens actively maintained stimulus representations ( sawaguchi et al . , 1988 ; sawaguchi and goldman - rakic , 1991 ; arnsten et al . , 1994 ) .
in contrast , da antagonists reduce both active maintenance related pfc activity , and also cause behavioral impairments in working memory and cognitive control tasks ( sawaguchi et al . , 1990 ; sawaguchi and goldman - rakic , 1994 ; williams and goldman - rakic , 1995 ) .
similar effects have been observed in human pharmacological and fmri studies , with da agonists ( administered systemically ) being associated with improvements in working memory and cognitive control , and leading to associated modulations of pfc activity ( kimberg et al . , 1997 ; gibbs and desposito , 2006 ) .
it is striking that the effects of pharmacological manipulations of da in pfc are so similar to the effects that have been observed from motivational manipulations ( leon and shadlen , 1999 ; watanabe et al . , 2002 ) .
these linkages between the role of da and pfc in motivation , and the effects of da modulation on pfc - mediated cognitive control functions have prompted the development of theories that explicitly link these two mechanisms .
the gating model account , put forward by braver and cohen ( 2000 ) , emphasized the importance of phasic da activity within pfc for the updating and active maintenance of goal representations .
specifically , this account suggests that the phasic da responses to cues signaling reward prediction could also be exploited as a means of learning which task - related information should be actively maintained in pfc , and when to update such information .
simulation studies demonstrated that a system could in fact learn appropriate updating and maintenance of task context or goal information based on reward prediction cues .
thus , this account suggests the possibility of a linkage between the reward / motivational and cognitive control functions mediated by da 
this point was made even more explicitly in the recent dual mechanisms of control framework ( braver et al . , 2007 ) , which specifically suggests that signals of reward motivation will bias cognitive control toward a  proactive  mode , in which task cues trigger sustained goal activation and maintenance in the service of preparation for anticipated control demands , via the aforementioned da  pfc interaction .
proactive control is distinguished from reactive control , in which the same task cues only trigger transient control related processes , rather than sustained active maintenance , under conditions of low da activity , such as when the environmental context is perceived to have reduced motivational value .
this account has been supported by recent experimental evidence from an fmri study of motivational influences on task - switching ( savine and braver , 2010 ) .
task trials that had high reward value were associated within increased activity in both lateral pfc and the midbrain da system .
moreover , the increased cue - related pfc activation on high reward trials was associated with behavioral measures of improved task preparation , supporting the idea of a reward - related shift toward proactive control . in summary ,
investigations of motivation and cognitive control have primarily focused on the role of goal representations in psychological models , and on interactions of the da system in pfc in neuroscience studies .
one mechanistic account suggests that da activity triggered by reward cues can serve as an updating and prioritization signal , that modulates active maintenance of goal information within pfc .
the potential similarity of the proposed mechanisms underlying both positive affect and reward motivation influences on cognitive control , according to the ashby model ( i.e. , cognitive changes due to increased dopamine release to cortical areas such as the pfc and acc ) , is striking , but has not yet been directly confirmed by experimental studies .
emotion and motivation are closely related constructs , but it is still not clear how to relate their influences on cognitive control . some theories do not clearly distinguish between the two , while others more explicitly state that emotion and motivation , while highly related , remain distinct constructs . given the state of current evidence , this is still a question calling for clarification .
most proposals regarding affective influences on cognitive control have not drawn a clean distinction between emotion and motivation .
this includes gray 's ( 2001 ) hemispheric specialization hypothesis , which explicitly does not distinguish between positive / negative emotion and approach / avoidance motivation , and ashby et al . 's ( 1999 ) dopaminergic theory of positive affect , which posits a relation between da and positive emotion because of da s involvement in reward processing . aarts et al .
( 2008b ) go even further , by explicitly suggesting an equivalence between positive emotion and reward motivation in terms of their effects on goal - pursuit and executive control . in their model ,
positive affective signals occurring in temporal proximity to activation of a cognitive goal should strengthen the maintenance , accessibility , and pursuit of that goal , regardless of whether those affective signals relate to goal attainment ( i.e. , whether or not they serve as direct reward motivation cues ) . despite these claims , the relationship between positive affect , approach motivation , and da system activity is somewhat tenuous .
experimental studies have shown that affective valence ( positive / negative ) and motivational direction ( approach / avoidance ) can be dissociated ( harmon - jones , 2003 ; harmon - jones and gable , 2009 ) .
likewise , in carver 's ( 2006 ) theoretical model , positive and negative affect emerge from detection of the rate of progress toward fulfilling either approach or avoidance - related goals : positive emotions result from above - anticipated goal progress ; negative emotions result from below - anticipated goal progress .
finally , in berridge s neuroscience - based account , dopamine is only critical for the transfer of motivational salience , or stimulus - triggered  wanting  to new cues or events , and does not generate hedonic experience , or  liking  ( which is thought to be represented in the ventral pallidum via neurochemicals such as opiates and endocannabinoids ; berridge , 2007 ; berridge et al . , 2009 ) .
thus , without supportive direct evidence , links between positive affect , approach motivation , and da system activity should not be assumed .
deconfounding emotional and motivational influences from one another is a challenge for exploring and clarifying these relationships .
we argue that , as a starting point , emotional and motivational manipulations need to be operationalized ( i.e. , with exposure to emotional stimuli during or just prior to the task , or motivational performance - contingent incentives , respectively ) and examined with performance - independent measures . examining psychophysiological signatures of these influences [ e.g. , startle reflex , facial electromyography ( emg ) ] that have been linked to valence but not motivational orientation of affective experiences ( cacioppo et al . , 1986 ; lang et al . , 1990 ) may be useful in dissociating these influences from one another .
although these influences have yet to be directly disentangled , independent empirical work from the emotion and motivation literatures indirectly hints that these are dissociable influences . while several theories have proposed that positive emotion can lead to cognitive broadening and flexibility ( isen et al . , 1987 ; ashby et al . , 1999
; fredrickson , 2004 ; rowe et al . , 2007 ) and exploration of alternate goals ( carver , 2003 ) , growing evidence suggests that reward incentives enhance goal maintenance / representation and influence proactive cognitive control ( savine and braver , 2010 ; padmala and pessoa , 2011 ) .
empirical evidence is mixed , suggesting that positive emotion and reward may have similar effects on some cognitive processes , such as task - switching ( reducing switch costs ; yan - mei and de - jun , 2008 ; savine et al . , 2010 ) , opposite effects on other processes , such as selective attention ( rowe et al .
, 2007 ; padmala and pessoa , 2011 ) and mixed results on yet other processes such as goal maintenance ( dreisbach and goschke , 2004 ; dreisbach , 2006 ; aarts et al .
how these diverging effects relate has yet to be systematically clarified , since positive affect and reward motivation have not yet been directly examined and compared .
nevertheless , there is at least one example from the literature in which the same experimental paradigm  the ax continuous performance task ( ax - cpt ; cohen and servan - schreiber , 1992 ; servan - schreiber et al .
, 1996 ; braver et al . , 2001 )  has been utilized ( in separate studies ) to explore the effects of positive affect and reward motivation on cognitive control .
the ax - cpt is a potentially advantageous paradigm for this purpose , because it permits selective examination of goal maintenance capability and proactive control .
however , surprisingly , the results of the positive affect and reward motivation studies appear to be somewhat different . under positive affect induction via valenced pictures displayed prior to each trial , participants showed evidence of reduced maintenance capability relative to neutral affect ( dreisbach , 2006 ) .
conversely , under manipulations of reward motivation , participants showed evidence of enhanced maintenance capability relative to baseline ( locke and braver , 2008 ) . in both studies ,
the results were interpreted as arising from modulation of da activity in pfc , but it is not clear if the two different manipulations actually led to similar or distinct effects within these brain systems .
thus , direct comparisons are clearly needed , with monitoring of neural activity , to determine whether there is a potential dissociation between positive affect and reward motivation effects on goal maintenance .
one possibility that is worth considering is that da activity in pfc underlies both positive affect - related reduction in maintenance capability and reward - related increases in maintenance capability , but that the two effects reflect dissociable temporal dynamics of da influence . in particular , it is well - accepted that da activity should be considered in terms of both tonic and phasic components , which can interact with each other ( grace , 1991 ) .
further , prior research has more strongly linked facilitation of goal maintenance with tonic da activation in pfc , primarily via d1 receptors ; in contrast , phasic da activity in pfc may promote updating and cognitive flexibility , potentially via d2 receptors ( cohen et al .
, 2002 ; oreilly and frank , 2006 ; durstewitz and seamans , 2008 ) .
thus , distinctions between reward motivation and positive affect may reflect a distinction in the balance between tonic versus phasic da activation and/or a d1 versus d2 dominated state .
however , the relationship between emotional and motivational processes and differential temporal dynamics of da activity has not been directly shown and has yet to be investigated .
the constructs of emotion and motivation are closely interrelated , and typically their influences on cognition have not been explicitly separated from one another ( e.g. , pessoa , 2009 ) . however , in the light of accumulating evidence suggesting they may be dissociable , their influences on cognition must be clarified .
as alluded to above , there are unresolved questions in this domain that provide promising routes for future investigation . here
a first , straightforward suggestion is for studies to be conducted that directly test and compare the effects of positive affect manipulations with those involving reward motivation within a single sample , and using closely matched experimental designs .
of course , this suggestion does beg the question of what exactly differentiates a positive affect manipulation from one involving reward motivation , especially since some studies advertised as examining positive affect have actually used manipulations involving delivery of rewards ( isen et al .
although this question is one that may involve a deeper discussion that is outside of the scope of this article , we want to highlight that this issue has not really been adequately considered by researchers working in this area . nevertheless , it is at least possible to operationalize a distinction in which positive affect is manipulated by influences such as mood inductions or strongly valenced stimuli , whereas reward motivation is manipulated by varying the incentives provided for task - performance .
with such an approach , it would be possible to directly test the hypothesis that positive emotion promotes cognitive flexibility while reward incentives promote greater goal maintenance . as mentioned previously , cognitive paradigms that specifically probe active maintenance and proactive control , such as the ax - cpt ,
could be used with emotional and motivational experimental manipulations to probe the possibility of dissociable versus common behavioral effects and/or their associated physiological bases .
other paradigms should also be examined , such as the remote associates and global / local paradigms , that have been frequently and fruitfully examined to demonstrate increased cognitive flexibility under positive affect ( isen and daubman , 1984 ; fredrickson and branigan , 2005 ; rowe et al . , 2007 ) , but have not previously been studied with respect to reward motivation .
finally , the use of a common paradigm would be useful for exploring other hypotheses relating to positive affect and/or reward motivation such as carver s coasting model .
unfortunately , this model has not previously been studied within cognitive experimental paradigms , so further work in how to operationalize maintained goal - pursuit versus goal - switching would need to occur ( e.g. , via exploration of potentially approach paradigms such as volitional task - switching ) .
a second promising direction for future research is a more direct examination of the role of neurotransmitter systems in mediating affective and motivational influences on cognitive control .
this is especially important with regards to the effects of positive emotion on cognition , since theories such as ashby s posit a neurotransmitter mechanism without direct evidence for its involvement .
study of the role of neurotransmitter systems in positive affect is somewhat challenging , since detecting positive affect in animal models is difficult ( although potentially not impossible , e.g. , berridge , 2000 ) , as is direct monitoring of neurotransmitter activity in humans .
however , studies that examine state - related changes in neurotransmitter receptor binding ( e.g. , using pet radioligand - labeling methods and dynamic imaging approaches ) do provide a promising avenue for this research , especially for the monitoring of da system activation ( egerton et al . , 2009 ) .
in particular , receptor binding studies may provide a powerful means of directly testing whether increases in positive affect are associated with increases in da system activity .
pharmacological manipulations provide another method by which to examine the link between neurotransmitter activity and cognitive change .
pharmacological challenge studies involving agents that influence da activity have been used fruitfully in a range of domains to understand the role of this system in cognitive functions such as working memory ( e.g. , cools et al . , 2007 ) , as well as in mediating basic aspects of reward processing ( e.g. , pessiglione et al . , 2006 ) .
thus , targeted studies are needed that directly investigate how pharmacological manipulation of this system impacts motivational versus affective effects on cognitive control .
although dopamine has received much attention for its involvement in reward and cognitive control processes , other neurotransmitters such as norepinephrine ( ne ) may also play crucial roles .
ne activity , historically linked to physiological arousal ( foote et al . , 1980 ) , is becoming increasingly appreciated as a complex and specific mediator in the control of behavior as well ( aston - jones and cohen , 2005 ) .
the locus coeruleus ( lc)-ne system may play a critical role in the regulation of exploitation ( i.e. , optimizing current task - performance ) and exploration ( i.e. , disengagement in search of alternative behaviors ) tendencies during task - oriented behavior  phasic and tonic ne activity may respectively reflect these control tendencies ; aston - jones and cohen , 2005 ) .
it may be that exploration is highly analogous to carver 's ( 2003 ) idea of  coasting  or that the exploitation  exploration balance is analogous to the maintenance - flexibility balance discussed with regard to dopamine and control ( dreisbach and goschke , 2004 ; muller et al . , 2007 ) , but connections between these bodies of work have yet to be made . in particular , it is still not well understood what the relative roles of dopamine and norepinephrine are in emotional and motivational interactions with cognition .
exciting new evidence suggests that pupil dilation can be used as a non - invasive marker of lc - ne activity in humans , with pupil dilation changes indexing shifts in the exploitation  exploration balance during performance of cognitive control tasks ( gilzenrat et al . , 2010 ) .
thus , pupillometric methods might be one promising avenue for exploring the role of the lc - ne system in affective versus motivational influences in cognitive control , along with the psychopharmacological and neurotransmitter imaging methods described above .
more generally , the use of psychophysiological measures may provide another approach by which possible dissociations between emotional and motivational influences on cognition can be investigated .
pupil dilation has been well - established to index fairly specific changes in cognitive demand and effort ( beatty , 1982 ; granholm et al . , 1996 ; beatty and lucero - wagoner , 2000 ) and thus may provide a measure of cognitive control , independent from behavior , that can finely index changes in temporal control dynamics .
for example , pupil dilation has been successfully utilized to examine the temporal dynamics of goal maintenance and proactive versus reactive control within the ax - cpt paradigm ( related to developmental changes ; e.g. , chatham et al . , 2009 ) .
additionally , pupil dilation is sensitive to emotional variables as well , and may reflect emotional arousal ( bradley et al . , 2008 ) .
thus , pupillometric methods might be exceptionally well - suited for examining interactions of affective / motivational systems and cognitive control , although such interactions have almost never been explored ( e.g. , satterthwaite et al . , 2007 ) .
skin conductance ( scr ) , startle probes , and emg are all well - established autonomic indicators of affective state ( bradley et al . , 2001 ) .
thus , comparison of the effects of affective versus motivational manipulations on these indicators might help to reveal potential dissimilarities in autonomic profile , as well as whether some indicators serve as better predictors of the cognitive control effects of such manipulations .
another means by which to probe for distinctions between emotion and motivation might be to more clearly assess the role of subjective experience .
subjective experience is thought to be a core ingredient to the construct of emotion ( barrett et al . , 2007 ) , but it remains unclear whether it should be considered key to the construct of motivation as well .
recent evidence suggests that subliminally presented reward cues can lead to similar effects on behavior and cognitive control as stimuli that are consciously perceived ( aarts et al .
2010 ) , suggesting that subjective awareness of motivational value is not critical . in the emotion realm
, subliminal information has been shown to influence affective preference ( zajonc , 1980 ) , and non - emotional facial changes ( i.e. , to a smile - like position ) have been associated with changes in emotional response ( strack et al . , 1988 ) .
however , subliminal presentation of positively valenced stimuli seems to only impact motivated behaviors such as the amount consumed and willingness - to - pay for rewards , but not subjectively experienced affective responses such as positive mood or reward liking ( winkielman et al . , 2005 ) .
thus , it is not clear whether subliminal manipulations of positive affect would impact cognitive control in the same manner as manipulations that are subjectively experienced . as a final consideration
, the relationship between emotion and motivation could be explored by examining the effect these manipulations have on each other .
some evidence suggests that reward incentives promote positive mood ( meloy et al . , 2006 ) , but such research is relatively sparse and , to our knowledge , effects of emotion on the effectiveness of a motivational manipulation remains unknown .
while emotion and motivation have been assumed to be related , they have largely been investigated independently with relation to cognitive control .
current theories suggest that the influences of positive emotion and reward incentives may depend on a common neuroanatomy : both may increase midbrain dopaminergic activity ( i.e. , ventral tegmental area ) , which projects to control - associated areas , such as the pfc and the acc .
the pfc in particular has received attention as a potential integration site for task and affective information in both emotional and motivational lines of research . despite these parallels ,
perhaps most fundamentally , the neurobiological mechanism , independent of reward , by which positive emotion influences cognition remain unclear .
specifically , there is as of yet no direct evidence that supports a model in which positive emotion , independent of other components of reward , is associated with dopamine activity .
clarifying this mechanism will be key to establishing whether positive emotion and reward motivation influences on cognitive control are common or distinct .
second , further exploration of differential contributions of tonic and phasic activity in both the da system and other relevant neurotransmitter systems , such as lc - ne , could help characterize both emotional and motivational influences on cognition , especially in probing further the hypothesis that positive affect and reward might be associated with more reactive and proactive ( and/or exploratory versus exploitative ) modes of cognitive processing , respectively .
third , inclusion of both psychophysiological measures and assessment / manipulation of subjective experience may be beneficial in theoretically distinguishing constructs of emotion from motivation and improving understanding of how they impact cognition .
fourth , effects of emotion and motivation on one another should be probed to help clarify their relationship .
emotions may be characterized as emergent from one s current status relative to one s optimal goal status ( carver , 2006 ; lang and bradley , 2008 ) .
thus , while emotion and motivation are closely related , emotions as an evaluator of goal status serve a slightly different functional purpose than motivations , and consequently may be more fluid in relation to any given goal .
accordingly , they may have a more variable influence on cognitive control relative to motivational influences , which serve to optimize goal - relevant processing directly .
clarifying these constructs will help unite disparate lines of research within a common theoretical framework , and provide a more nuanced picture of these interactions and their complexities . by doing so
, this research effort may help to significantly advance the emerging field of affect  cognition interactions .
the authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest .
 it is becoming increasingly appreciated that affective influences can contribute strongly to goal - oriented cognition and behavior . however , much work is still needed to properly characterize these influences and the mechanisms by which they contribute to cognitive processing . 
 an important question concerns the nature of emotional manipulations ( i.e. , direct induction of affectively valenced subjective experience ) versus motivational manipulations ( e.g. , delivery of performance - contingent rewards and punishments ) and their impact on cognitive control . 
 empirical evidence suggests that both kinds of manipulations can influence cognitive control in a systematic fashion , but investigations of both have largely been conducted independently of one another . 
 likewise , some theoretical accounts suggest that emotion and motivation may modulate cognitive control via common neural mechanisms , while others suggest the possibility of dissociable influences . here , we provide an analysis and synthesis of these various accounts , suggesting potentially fruitful new research directions to test competing hypotheses . 
Introduction
Emotion and Motivation: Terminology and Conceptualization
Positive Affect and Cognitive Control
Reward Motivation and Cognitive Control
Emotion Versus Motivation: Common or Dissociable Influences?
Directions for Future Research
Summary and Conclusion
Conflict of Interest Statement