1. Introduction

Responsiveness to feedback is a fundamental aspect of learning (e.g., [1]). Principles of operant conditioning clearly express the common ways in which the outcome of current behaviour influences future action [2]. While changing action as a consequence of negative outcome (ie, lose-shift) and repeating action as a consequence of positive outcome (ie, win-stay) seem to be two sides of the same coin, punishment and reinforcement remain anatomically [3], evolutionarily [4, 5] and mechanistically [6, 7] distinct. In addition to operating in environments such as gambling and education- where feedback is both salient and explicitly negative or positive- there are other cases where information regarding our performance is often ambiguous or incomplete [8]. The interpretation of outcomes that do not have a clear valence, either as a result of the absence of feedback (ambiguous; [9]) or the explicit delivery of neutral feedback, such as the zero value assigned to drawing against an opponent [10], is a neglected feature of the decision-making literature.

The behavioural and neural responses following supposedly ‘neutral’ outcomes have provided a number of unique insights into the subjective aspects of decision-making. Within a simple case where three possible outcomes of a competitive interaction are assigned different values (win = +1, draw = 0, lose = -1), a draw may co-opt aspects of positive or negative outcomes as a result of the transient state of the organism (see [11]). [5] (2001, p. 225) express this interpretive tension generated by draws as “to tie is to fail to win, but on the other hand to tie is to avoid a loss.” Thus, a draw may be perceived as worse-than-expected in the context of not winning, or better-than-expected in the context of not losing. This need for personal interpretation means that individuals- in otherwise identical environments in which they encounter the same types and frequencies of outcomes- can form different subjective states where they experience more successes than failures (i.e., [win = draw] > lose), or, more failures than successes (i.e., win < [draw = lose]). This is important for at least two reasons. First, given the inherent ambiguity of draws, these responses can speak to the degree of optimistic bias or depressive realism held as a trait [12, 13]. Second, draws play a critical component in determining gambling behaviour, since a draw could be equally perceived as either a near-win or a near-loss thereby perpetuating erroneous beliefs in performance success [14, 15]. Given the ubiquity of traditional operant conditioning responses to clear gains and losses (win-stay, lose-shift), it seems probable that the behavioural profile for draw outcomes has its hallmark in these more hard-wired reactions. We can start to understand the subjective interpretation of draws by comparing performance with explicitly positive and negative outcomes, in addition to reviewing the previous literature in terms of a number of metrics including decision times, neural flexibility, and, the quality and optimality of action following outcome.

With respect to decision time, we can draw from the literature on post-loss slowing / speeding (c.f., impulsivity; [16–18]). Here, differences in future decision time are determined by the type of outcome caused by the current action: post-loss slowing is defined as increased decision time following losses relative to wins, and, post-loss speeding is defined as decreased decision time following losses relative to wins. A contributing factor in the observation of slowing or speeding is the degree to which failure is rare [19]. For example, if an individual interacts with an opponent who cannot be beaten (unexploitable), or interacts with an opponent who can be beaten (exploitable) but who the participant fails to beat, then performance is characterized by post-loss speeding. In contrast, the degree to which individuals successfully exploit an opponent increases the magnitude of post-loss slowing (see [20]; Fig 1). However, outcome frequency does not provide a complete account of post-loss slowing since post-loss slowing is intact when positive and negative outcomes are experienced to the same degree (eg., [21]). Previous data utilizing draw outcomes further show that when participants engage with unexploitable opponents where long-run outcome frequencies were equivalent, decision times following wins were slower than decision times following both losses and draws (i.e., post-draw speeding; [21, 22]). Therefore, decision time speeding data establish a connection between neutral (draw) outcomes and explicitly negative (lose) outcomes.

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Fig 1. Left column depicts proportion of shift behaviour following wins, losses and draws as a function of cumulative score presentation (score, no score) and the value of draws (0, +1, -1; Experiment 1), (+1, -1; Experiment 2), or, the value of losses (-2) and wins (+2; Experiment 3).

Horizontal grey dotted line represents optimal performance (66.6%). Right column depicts subsequent reaction time following wins, losses and draws. Error bars represent standard errors.

https://doi.org/10.1371/journal.pone.0270475.g001

A second metric to ascertain the subjective interpretation of draws is the response of the brain following outcomes. Feedback-related negativity (FRN; [23]) is a scalp-recorded electrical potential related to dopaminergic influences on anterior cingulate cortex (ACC; [24]) and is a reliable index of the positive or negative nature of trial outcome [25]. Paradigms directly using neutral outcomes have shown that FRN amplitudes generated following draws are often statistically indistinguishable from unambiguously negative (i.e., lose) outcomes (e.g., [10, 25, 26]). In contrast, both lose and draw trials generate larger FRN amplitude than unambiguously positive trials (i.e., win; e.g., [27, 28]). Therefore, event-related potential data also align draws with a negative rather positive interpretation.

Of final interest is the flexibility of behaviour exhibited following outcome. Operant conditioning dictates the tendency to repeat action following success (win-stay) and the tendency to switch action following failure (lose-shift). Under baseline conditions (win = +1, draw = 0, loss = -1), the degree of win-stay behaviour approximates the optimal proportion (33.3%) as predicted by a mixed-strategy-style approach guaranteeing the absence of exploitation (see [10, 21; Experiment 1]). In contrast, the degree of lose-shift behaviour exceeds the optimal proportion (66.6%), making participants more predictable following loss. In follow-up studies [22], the objective values of losses and wins was manipulated relative to baseline (see also [6, 29]). Data produced by these schemes showed that value manipulations changed behaviour for wins but not for losses [6, 22]. Specifically, even when the objective cost of losing was reduced to half the gain of winning (-1, +2), participants still exhibited robust lose-shift behaviour to the same degree observed in a baseline condition (-1, +1) or a condition in which the objective cost of losing was doubled relative to the gain of winning (-2, +1). In contrast, win-stay behaviour was more flexible and significantly increased when wins and losses had different objective values. Therefore, negative outcomes are characterized by subsequently less flexible shift behaviour, whereas positive outcomes are characterized by subsequently more flexible stay behaviour. One of the basic principles of loss aversion is that losses have roughly twice the subjective magnitude of their objective value [22, 30, 31]. Therefore, the inflexibility of shift behaviour following loss might be associated with the greater subjective value of negative relative to positive outcomes.

From our previous data however, we note a seemingly reliable observation that prohibits the wholesale acceptance of draws as functionally equivalent to losses. For example, in [18] (Experiment 1, no credit condition), the degree of shift behaviour is smaller following draws relative to losses (76.63% vs. 70.62%; t[39] = -2.267, p = .029; n = 40). Similar reductions in shift behaviour following draws relative to losses were also extracted from [10) (Experiment 1: 72.53% vs. 78.51%; t[35] = -2.530, p = .016; n = 36), [22] (baseline condition; 71.97% vs. 77.68%; t[35] = -2.120, p = .041; n = 36), and, [21] (70.63% vs. 75.89%; t[30] = -2.307, p = .028; n = 31). Given the attenuation of shift bias following draws relative to losses, then there is clearly some sense in which these are not identical examples of negative outcomes. Draws generate a less negative state, which enables the individual to approach optimized performance in the long run (ie 66.6% shift behaviour).

2. Experiment 1

In Experiment 1, participants engaged in the three-response game Rock, Paper, Scissors using a novel objective value manipulation for draws (+1, 0, -1). Critically, performance was evaluated against a computerized opponent playing according to a mixed-strategy variant, where each of the three responses appeared 33.3% of the time, in a random order. (MS; [32–34]).

In principle, playing against an opponent operating according to MS should guarantee- in the long run- an equivalent number of wins, losses and draws. Thus, when the opponent is unexploitable, there is no reliable model of successful performance for participants to acquire. Once again, this type of performance is critical for the current debate as it allows the same exposure to positive (win), neutral (draw) and negative (lose) outcomes. Starting at the position that draws are objectively neutral (0), we consider the consequences of making the value outcome of draws equivalent to wins (+1) and losses (-1). If objective value is the only factor contributing to performance, then the behavioural changes we see when draws are assigned +1 and -1 should be of the same magnitude. If value and valence interact, then the behaviour following +1 and -1 draws should be different. Since draws are observed to have both behavioural [21, 22] and neural [25, 27] hallmarks similar to objectively negative outcomes (losses), moving the value to +1 should be a more salient manipulation than moving the value to -1.

Changing draw value from 0 to +1 or -1, and evaluating performance against an unexploitable opponent in Experiment 1, we make the following predictions. This is guided by data from 12 previously published experiments that use a similar win (+1), draw (0), lose (-1) outcome value assignment against an opponent who cannot be beaten [10, 18, 20–22, 35]. First, reaction times following draws should be faster than reaction times following wins (post-draw speeding). Second, actions following draws should be more likely to elicit shift than stay behaviour, once again aligning with the consequences of losing rather than winning. Third, the degree to which participants stray from optimal performance should be greater for draw-shift than win-shift, consistent with the behavioural sub-optimality often associated with negative relative to positive outcomes. The expected value for all shift behaviour is 66.6%. Fourth, if draws are interpreted as negative when assigned the value of 0, changing the value of the draw to +1 (i.e., moving from subjectively negative to objectively positive) should alter behaviour more than changing the value of the draw to -1 (i.e., moving from subjectively negative to objectively negative).

2.2 Results

Statistica 13.3 (TIBCO Software) was used to analyze the data. The comparison of wins (32.92%), loses (33.97%) and draws (33.12%) collapsed across condition was not significant according to a one-way repeated-measures ANOVA [F(2,78) = 1.274, MSE < .001, p = .286, ƞ_p² = .031], suggestive of long-run equivalence of outcomes in Experiment 1. Median RTs on trial n following wins, loses and draws at trial n-1 were compared across the three conditions (draw value: +1, 0, -1) in a two-way repeated-measures ANOVA (see right-hand panel of Fig 1). Only a significant main effect of outcome was revealed [F(2,78) = 6.334, MSE = 107065, p = .003, ƞ_p² = .140], with significant speeding for draws (502 ms) relative to wins (hence, post-draw speeding; 650 ms; Tukey’s HSD, p = .002) but not between losses (553 ms) and wins (p = .062). The main effect of draw value [F(2,78) = 0.327, MSE = 207042, p = .722, ƞ_p² = .008], and, the interaction between draw value x outcome [F(4,156) = 2.136, MSE = 43307, p = .003, ƞ_p² = .052] were not significant.

The proportion of shift behaviour following wins, losses and draws was calculated from the last 119 trials in each block (the first trial has no history; see Table 1). In this way, an observed value less than the expected value of 66.6% represents a bias towards stay behaviour, where an observed value more than the expected value of 66.6% represents a bias towards shift behaviour. Shift proportions were compared across outcome (win, lose, draw) and draw value (+1, 0,-1) in a two-way repeated-measures ANOVA (see left-hand panel of Fig 1; the horizontal grey line represents the expected value of 66.6%). The main effect of draw value was not significant [F(2,78) = 0.215, MSE = .029, p = .807, ƞ_p² = .005], nor was the interaction between draw value x outcome [F(4,156) = 2.420, MSE = .010, p = .051, ƞ_p² = .058]. A significant main effect of outcome [F(2,78) = 16.874, MSE = .025, p < .001, ƞ_p² = .302] demonstrated that the degree of shift behaviour for wins (64.35%) was smaller than that for both losses (76.17%) and draws (70.70%). The degree of draw-shift behaviour was also significantly smaller than the degree of lose-shift behaviour (all Tukey’s HSD, p < .05).

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Table 1. Distribution of item, outcome, outcome-response contingency and reaction time, and randomness deviation as a function of the value of draw trials (+1, 0, -1) in Experiment 1.

Standard error in parenthesis.

https://doi.org/10.1371/journal.pone.0270475.t001

Observed shift proportions following wins, losses and draws were also compared to the expected value predicted by the participant playing according to MS (66.6%) via one-sampled t-tests. Neither win-shift (t[39] = 0.875, p = .387) nor draw-shift (t[39] = 1.885, p = .067) was significantly different from expected value, but lose-shift (t[39] = 5.163, p < .001) proportions did supporting a significant bias towards shift behaviour following losses.

3. Experiment 2

The data from Experiment 1 identified distinct behavioural effects that underline the ambiguities associated with draws. Draws were aligned with negative outcome in that future actions were characterized by speeding rather than slowing, and, shift rather than stay behaviour, similar to losses. However, draws did not generate identical states as losses, since the degree of shift behaviour was equivalent to MS performance in the former case. Draws were also weakly aligned with positive outcomes in that the degree of shift behaviour was constant when the value of the draw was made explicitly positive but rose (non-significantly) when the value of the draw was made explicitly negative. In Experiment 2, we focused more specifically on the hypothesis that shift behaviour should increase- away from MS performance- via the explicit assignment of draw value equivalent to losses (-1) compared to wins (+1; c.f., [38]).

We also considered the contribution of a potentially hidden variable in Experiment 1- namely, the presence of a cumulative score. In addition to the immediate effect of adding or subtracting individual points on a trial-by-trial basis, cumulative scores provide a longer-range index of success or failure. This subjective, longer-range evaluation of outcome has support at a neural level, given the observation that the anterior cingulate cortex (ACC) represents current outcomes against the broader context of average task value [39]. In particular, the presence of such cumulative scores may have been particularly important in Experiment 1 exactly due to the manipulation of draw value. Since MS opponents were used in all three conditions, participants experienced a broadly equivalent number of wins, draws and losses. Therefore, the degree of success / failure was equivalent across conditions. However, when draw outcomes were assigned to non-zero values, the use of +1 guaranteed an increasingly positive score as the block progressed, in contrast to the use of -1 guaranteeing an increasingly negative score. This is clearly borne out in the data from Experiment 1: the final average score when draw = 0 was -3.00 (SE = 1.30), when draw = +1 was +39.25 (SE = 1.85), and, when draw = -1 was -38.65 (SE = 1.72; F[2,78] = 628.15, MSE = 96.84, p < .001, ƞ_p² = .942; one-way repeated measures ANOVA, all comparisons, Tukey’s HSD p < .05).

Therefore, it is possible that experiencing an increasingly positive or negative score impacts upon any immediate effects generated by individual trial-by-trial outcome values [39]: positive scoring (+1) become less salient against a backdrop of a reliably increasing total, just as negative scoring (-1) becomes less salient against a backdrop of a reliably decreasing total. Consequently, in Experiment 2, the central manipulation of draw value in accordance with explicitly positive (+1) or explicitly negative (-1) outcomes was combined with the manipulation of the presence or absence of a cumulative score.

3.2 Results

As in Experiment 1, the comparison of wins (33.39%), losses (33.75%) and draws (32.85%) was not significant [F(2,708) = 0.757, MSE < .001, p = .473, ƞ_p² = .021; see Table 2]. Median trial n RTs were submitted to a three-way repeated-measures ANOVA featuring draw value (+1, -1), cumulative score (present, absent) and outcome on trial n-1 (win, lose, draw). Only the two-way interaction between cumulative score x outcome was significant: [F(2,70) = 5.42, MSE = 18945, p = .006, ƞ_p² = .134]. The interaction showed both post-loss speeding (384 ms) and post-draw speeding (434 ms) relative to RTs following wins (510 ms) but only in cases where the cumulative score was present (Tukey’s HSD, ps < .05).

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Table 2. Distribution of item, outcome, outcome-response contingency and reaction time as a function of the value of draw trials (+1, -1) and presence (S) or absence (NS) of cumulative score in Experiment 2.

Standard error in parenthesis.

https://doi.org/10.1371/journal.pone.0270475.t002

Reaction times when the cumulative score was present following wins were also slower than all outcomes when the cumulative score was absent (384, 372, 403 ms for losses, draws and wins, respectively). All other comparisons were non-significant, with the interaction arising from the magnitude of post-loss and post-draw speeding decreasing without cumulative score. In these respects, the presentation of an increasingly positive-going / negative-going score would appear to be a prerequisite for the reliable observation of speeding following ‘negative’ outcomes.

All other main effects and interactions were not significant: cumulative score main effect [F(1,35) = 3.029, MSE = 112624, p = .091, ƞ_p² = .079], draw value main effect [F(1,35) = 1.347, MSE = 63459, p = .254, ƞ_p² = .037], outcome main effect [F(2,70) = 2.789, MSE = 71944, p = .068, ƞ_p² = .074], cumulative score x draw value interaction [F(1,35) = 0.004, MSE = 65721, p = .950, ƞ_p² < .001], draw value x outcome interaction [F(2,70) = 1.105, MSE = 17437, p = .337, ƞ_p² = .031], and, the three-way interaction [F(2,70) = 1.052, MSE = 25991, p = .355, ƞ_p² = .022].

Shift proportions were compared across draw value, cumulative score and outcomes in a three-way repeated-measures ANOVA (see Fig 1). Shift proportions were significantly modulated by a main effect of draw value [F(1,35) = 5.165, MSE = 0.042, p = .029, ƞ_p² = .129], a main effect of outcome [F(1,35) = 8.500, MSE = 0.069, p < .001, ƞ_p² = .195], and, an interaction between draw value x outcome [F(2,70) = 5.080, MSE = 0.017, p = .009, ƞ_p² = .126]. Here, win-shift did not differ as a function of draw value (-1 = 61.99%; +1 = 58.38%), nor did lose-shift (-1 = 72.74%; +1 = 72.58%). However, draw-shift behaviour was significantly larger when draws were assigned the value of -1 relative to +1 (73.73% and 63.98%, respectively; Tukey’s HSD, p < .05). According to one-sampled t-tests, draw-shift behaviour when draws were assigned the value of +1 did not significantly differ from the expected value of 66.6% (63.98%; t[35] = -0.892, p = .378) but did show a significant bias in favour of shift behaviour when draws were assigned the value of -1 (73.73%; t[35] = 3.105, p = .003). Behaviour following wins showed a significant bias in favour of stay (60.18% shift; t[35] = -2.214, p = .033), whereas behaviour following losses showed a significant bias in favour of shift (72.66% shift; t[35] = 2.269, p = .030).

All other main effects and interactions of the ANOVA were non-significant: cumulative score main effect [F(1,35) = 0.052, MSE = 0.048, p = .821, ƞ_p² = .001], draw value x cumulative score interaction [F(1,35) = 0.097, MSE = 0.021, p = .758, ƞ_p² = .003], draw value x outcome interaction [F(2,70) = 0.201, MSE = 0.017, p = .819, ƞ_p² = .005], and, the three-way interaction [F(2,70) = 0.333, MSE = 0.008, p = .718, ƞ_p² = .009].

Experiment 2 produced a significant effect of draw value, wherein the degree of shift behaviour was increased when draw trials were assigned the same valence and value as lose trials. This was confirmed by further analysis of the degree of draw-shift as a function of draw value (+1, -1) and Experiment (1, 2 [score present conditions only]) via a mixed, two-way ANOVA. The main effect of draw value [F(1,74) = 9.353, MSE = .018, p = .003, ƞ_p² = .112] in the absence of a main effect of Experiment [F(1,74) = 0.558, MSE = .049, p = .457, ƞ_p² = .007], or interaction with Experiment [F(1,74) = 0.778, MSE = .017, p = .381, ƞ_p² = .010] confirms that the proportion of draw-shift behaviour increased when draws were assigned the value of -1 relative to +1 (73.25% vs. 66.69%, respectively). Once again, draw-shift behaviour exceeded that predicted by MS when draws were assigned a negative value (t[75] = 3.630, p < .001) but was equivalent to MS behaviour when draws were assigned a positive value (t[75] = 0.067, p = .947), on the basis of one-sampled t-tests.

4. Experiment 3

4.2 Results

As in all previous experiments, the occurrence of wins (33.16%), losses (33.46%) and draws (33.38%) was equivalent [F(2,70) = 0.099, MSE < .001, p = .906, ƞ_p² = .002; see Table 3]. Median RTs from trial n were submitted to a three-way repeated-measures ANOVA featuring value (win-heavy, lose-heavy) and cumulative score (present, absent) and outcome at trial n-1 (win, lose, draw). The two-way interaction between cumulative score x outcome found in Experiment 2 replicated in Experiment 3: [F(2,70) = 3.340, MSE = 48207, p = .041, ƞ_p² = .087] in addition to a main effect of outcome: [F(1,35) = 7.321, MSE = 85044, p = .001, ƞ_p² = .173].

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Table 3. Distribution of item, outcome, outcome-response contingency and reaction time as a function of the value of win (+2) and lose (-2) trials and presence (S) or absence (NS) of cumulative score in Experiment 3.

Standard error in parenthesis.

https://doi.org/10.1371/journal.pone.0270475.t003

As in Experiment 2, post-loss speeding (519 ms) and post-draw speeding (481 ms) relative to RTs following wins (658 ms) were only observed in the condition where the cumulative score was present (Tukey’s HSD, ps < .004). Reaction times when the cumulative score was present following wins were also slower than all outcomes when the cumulative score was absent (498, 405, 453 ms for wins, losses and draws, respectively). Post-loss speeding was also significant in the cumulative score absent condition (Tukey’s HSD, p = .030) and all other comparisons were non-significant.

All other ANOVA main effects and interactions were not significant: cumulative score main effect [F(1,35) = 3.361, MSE = 325091, p = .075, ƞ_p² = .088], value main effect [F(1,35) = 0.553, MSE = 149089, p = .462, ƞ_p² = .016], cumulative score x value interaction [F(1,35) = 0.010, MSE = 434503, p = .919, ƞ_p² < .001], value x outcome interaction [F(2,70) = 1.357, MSE = 39730, p = .264, ƞ_p² = .037], and, the three-way interaction [F(2,70) = 2.298, MSE = 31233, p = .108, ƞ_p² = .062].

Shift proportions were analysed across value (win-heavy, lose-heavy),cumulative score (present, absent) and outcome (win, lose, draw) in a three-way repeated-measures ANOVA (see Fig 1). A main effect of outcome was noted [F(2,70) = 14.632, MSE = 0.077, p < .001, ƞ_p² = .295], along with an interaction between value x outcome [F(2,70) = 3.597, MSE = 0.010, p = .033, ƞ_p² = .093]. None of the pairwise comparisons between value were significant (win: win-heavy = 57.76% vs lose-heavy = 61.27%; lose: win-heavy 78.44% vs. lose-heavy = 75.80%; draw: win-heavy = 66.73% vs. lose-heavy = 68.52%; all Tukey’s HSD, p > .05). Aggregate behaviour following win was not significantly different from the expected value of 66.6% (59.51%; t[35] = -1.909, p = .065), aggregated behaviour following lose was significantly biased towards shift (77.12%; t[35] = 4.174, p < .001), and aggregated behaviour following draw was not significantly different from the expected value of 66.6% (67.62%; t[35] = 0.363, p = .719).

5. General discussion

In the absence of explicit reinforcement or punishment, we must still evaluate the relative success or failure of our actions and prepare for future behaviour accordingly. The current data speak clearly to outcome instances which are- on the surface- neither gains nor losses.

Previous data have strongly argued for the draw experience to elicit negative rather than positive responses. For example, models of human performance are better when draws are directly punished in the same way as losses (that is, assigned the value of -1), rather than being neither punished nor rewarded (assigned the value of 0; [38]). Similar profiles for draws and losses are shown in terms of a speeded bias towards shift behaviour, further implying their subjective interpretation as negative rather than positive (e.g., [22, 41]). While our data also support the contention that responses following draws will be initiated faster than those following explicit wins, and, that draws produce a future response switch (rather than stay) bias, the experience of draws is not wholly negative. This is borne out in the logic that fast rather than slow reaction times following loss represent a self-imposed limitation on future decision-making time that makes automatic, sub-optimal performance more likely ([10, 18, 31]). However, the post-draw speeding observed in the current experimental series did not produce the same sub-optimal performance as that observed for post-loss speeding. The average proportion of draw-shift behaviour was equivalent to that predicted by mixed-strategy performance wherein all three possible response associations between consecutive trials were equal (draw-stay ≈ 33.3%; draw-shift ≈ 66.6%). Such performance guarantees loss minimization and matches the approximation of mixed-strategy performance often observed following wins.

Moreover, draws allowed for a greater degree of behavioural flexibility relative to outcomes that were clearly marked as negative. Our data show that changing the value of draws also leads to changes in behaviour- specifically, assigning draws the value of explicit wins (+1) enabled an approximation of optimal behaviour (see above). In contrast, assigning draws the value of explicit losses (-1) lead to an increase in shift bias thereby placing the participant in a potentially precarious and exploitable competitive position (see Fig 1). These comparisons strongly suggest another way in which draws can behave like wins rather than losses. The suggestion that the draw outcome as chameleon-like in nature, however, must be tempered by additional observations. Based on a reviewer’s suggestion, we examined the degree of shift behaviour following wins (+1; 61.99%) in Experiments 1 and 2 against the concomitant behaviour generated by draws (+1; 66.62%) within those same conditions. We noted a significant reduction in win-shift behavior relative to draw-shift behaviour, when both categories were assigned a constant value of +1 t[75] = -3.051, p = .003. Similarly, we examined the degree of shift behaviour following losses (-1; 74.10%) in Experiments 1 and 2 against the concomitant behaviour generated by draws (-1; 73.69%), we noted a non-significant difference in lose-shift behavior relative to draw-shift behaviour, when both categories were assigned a constant value of -1: t[76] = 0.292, p = .771. Our reading of these results are that draw outcomes may more readily co-opt the behavioural signatures of explicitly negative, relative to explicitly positive, outcomes when the same values are assigned. If a +1 draw does not have the exact same properties as a +1 win, then value in and of itself cannot completely predict the behavioural consequences of outcomes.

Thus, the study of neutral outcomes will continue to represent an important addition to decision-making for two reasons. First, our current data imply a cognitive flexibility following draw trials that is not triggered by more clearly valenced wins and losses. This provides a clear route to studying the subjective aspects of outcome response, and how reaction to neutral trials may be shaped by preceding trial history. For example, we have recently shown that relative to draw-draw trials, the trial outcome sequence of win-draw causes an increase in shift behaviour whereas the sequences of lose-draw causes a decrease in shift behaviour- at least at a group level [11]. The concomitant increase and decrease in shift behaviour appears to us as an objective manifestation of the subjective nature of signed prediction error theory (eg, [42, 43]). In other words, draw trials preceded by a win are interpreted as worse-than-expected (making the draw appear more negative) whereas draw trials preceded by a loss are interpreted as better-than-expected (making the draw appear more positive). Second, introducing a third outcome (draw) requires a concomitant increase in the number of responses within the decision-making space. This is important as there are growing concerns as to the degree to which the modal use of binary decision-making paradigms severely limits our understanding of more naturalistic, non-binary decision spaces [44, 45].

In sum, mitigating the adverse emotional and cognitive consequences of negative outcomes remains an important goal in the context of education, gambling and economics. However, our data show that moving away from binary conceptualizations of outcome is critical to understanding the full palette of subjective responses elicited by decision-making. Specifically, our consideration of draws highlights the subjective aspects of decision-making, and the ways in which supposedly neutral outcomes take on the hues of more clearly valenced results. The processing cascade generated by neither being explicitly reinforced or punished produces a complex behavioural profile containing elements found in both explicitly positive and explicitly negative results. The reaction to draws appears more flexible than those produced by wins and losses, and generates a response signature that is simultaneously positive and negative, but apparently never ‘neutral’.

Supporting information