In this study we were unable to replicate several of the critical findings presented by Gard et al. (2006
and other studies (Favrod et al., 2009
; Chan et al., 2010
; Loas et al., 2010) concerning the TEPS. We found that individuals with SZ differed from controls in their ratings of consummatory but not anticipatory pleasure—the opposite of the pattern previously reported. It is important to note that our control participants did receive significantly higher scores on the TEPS-CON scale than those reported in Gard et al. (2007)
(TEPS CON: Gard et al. = ~4.52 vs. 4.96 in our sample; t = 3.67, p
= 0.01). However, control scores on the TEPS-ANT scale are highly consistent with those reported in Gard et al. (2007)
(TEPS ANT: Gard et al. = ~4.48 vs. 4.50 in our sample; t = 0.15, p
= n.s.). Although our control sample, obtained via random digit dialing, is highly representative of the individuals in our community and well-matched with the patient sample in terms of demographics, it is nonetheless possible that a selection bias in control groups could account for differences in findings on the TEPS-CON between the present investigation and previous ones.
It is also important to note that patient self-report on the TEPS-CON (M = 4.36) was nearly identical to that of Gard et al (2007)
(M = 4.33); however, our patients reported greater anticipatory pleasure (M = 4.48) than Gard et al. (2007)
(M = 4.04). It therefore appears that the main difference in findings across the two studies is that we failed to replicate the finding that individuals with SZ receive significantly lower anticipatory pleasure scores. We also failed to replicate group differences that have previously been reported among high and low negative symptom patients and controls on the TEPS-ANT in a Chinese sample (Chan et al., 2010
) and significant correlations with the SANS in a French-speaking sample (Favrod et al., 2009
). Our failure to replicate these previous results on the TEPS does not appear to be due to abnormal self-report or characteristics of the patients or controls in our sample, as individuals with SZ and controls in the current sample exhibited patterns of performance similar to other published studies on the Chapman Anhedonia and BIS/BAS scales.
Interestingly, our pattern of correlations observed between the TEPS and the BIS/BAS and Chapman Anhedonia scales was largely consistent with findings from Gard et al. (2007)2
. Similar to Gard et al. (2007)
, we also found that: 1) the TEPS scales were not correlated with the BIS, but were positively correlated with the total BAS score; 2) the TEPS-ANT scale was robustly correlated with the BAS Reward Responsiveness subscale, 3) the TEPS scales were negatively correlated with Chapman Scale Physical Anhedonia; 4) Chapman Social Anhedonia was negatively correlated with TEPS-ANT, but not TEPS-CON. However, we also failed to replicate several correlational findings reported in Gard et al. (2007)
, as we found that the TEPS-CON was significantly correlated with BAS Reward Responsiveness and that the TEPS-ANT scale correlated unexpectedly with the severity of BPRS positive symptoms. This pattern of findings strengthens the interpretation of the current findings on null group differences. That is, our TEPS findings are not simply a byproduct of some peculiar responses on the TEPS that are inconsistent with prior reports. Rather, we show substantial replication of the pattern of correlations observed in Gard et al. (2007)
, and find meaningful associations across multiple measures. The validity of patient self-report in the current study is also strengthened by the fact that the scales were internally consistent in both patients and controls and showed reasonable stability over time. Thus, the validity of the patient self-report in the current study does not seem in question- we simply did not replicate the finding of intact consummatory and impaired anticipatory pleasure that has been found in other studies using the TEPS.
We do not have a ready explanation for the differences in findings across studies. Both studies involved groups of stably treated outpatients with long established illness. While there are some demographic differences across the studies3
it would be hard to explain why any such difference would selectively impact performance on ratings of anticipatory versus consummatory pleasure. One of the main differences across samples appears to be the percentage of patients prescribed conventional vs. atypical antipsychotics. In the present study, only 12% of patients were prescribed typical antipsychotics, compared to 31% in Gard et al. (2007)
, and 29% in Chan et al. Given previous evidence indicating that typical antipsychotics result in more reward prediction dysfunction (Juckel et al., 2006
), it is possible that conventional antipsychotics play an important role in producing anticipatory pleasure deficits. It is also important to note that our sample of schizophrenia patients, while large, had a greater proportion of individuals prescribed clozapine than what is common in many samples. This likely reflects the long history of clozapine clinical trials conducted at MPRC, resulting in clinicians having more experience using the drug than is common in community. However, the lack of significant differences between individuals with SZ prescribed clozapine vs. those not prescribed clozapine in the current sample argues against clozapine being responsible for the different pattern of results across studies. In the Gard et al (2007)
study, only 1 patient was prescribed clozapine, yet their sample had higher mean BPRS total scores than patients in the current study. The patients in Gard et al. (2007)
therefore appear to be more globally symptomatic, yet less likely to be on clozapine, potentially suggesting that anticipatory pleasure is more related to symptom severity than treatment resistance. In line with this possibility, our data suggest that greater severity of psychosis is associated with lower self-reported anticipatory pleasure. It therefore appears that additional research is needed to determine the roles of conventional antipsychotics and psychotic symptoms in anticipatory pleasure.
It is also noteworthy that we were able to observe differences on the TEPS-CON scale, which proved to be the more stable of the two subscales in our sample of 19 individuals with SZ who completed the measure across two time points. Differences in the consistency of measurement across the two time points did not appear to be due to changes in clinical symptoms, therefore suggesting that the lower consistency noted for the TEPS-ANT might be due to relatively lower stability of this scale (which is still high by most standards). However, it is also possible that anticipatory pleasure is not as “trait-like” as consummatory pleasure, and that it may be influenced by a number of unique outside factors. If anticipatory pleasure is in fact more susceptible to being influenced by such factors, this could certainly explain the lower stability of the TEPS-ANT scale. Given that the TEPS primarily examines physical pleasure, it may be beneficial for future studies to examine the possibility that anticipatory pleasure is more affected in other domains of pleasure, such as social, recreational, or intellectual domains.
While our empirical results are disappointing, we continue to believe that the theoretical approach embedded in the TEPS, distinguishing between different aspects of reward experience and pleasure, may provide a way forward in understanding the nature of anhedonia and broader motivational deficits in individuals with SZ. Indeed, we were motivated to do this study because we considered the preliminary evidence for the construct validity of the TEPS, gathered in both healthy controls and in SZ, to be extremely promising, and therefore, our results are surprising and disappointing. It will only be possible to determine if the different findings across studies is a result of sampling error with the study of additional SZ cohorts. Future studies examining these aspects of anhedonia will benefit from using additional behavioral, experience sampling, and psychophysiological measures in conjunction with the TEPS.
The TEPS presents an unusual task demand that might explain the variable findings to date. In order to rate TEPS items, a participant must be able to call into mind some kind of representation of the “value” of the experiences that are being probed. The distinctions that are made between how excited one is before an experience versus during or after an experience, are very subtle and may often be represented in one overall schema. It is clearly plausible that some people may be better at searching through these memories and making subtle value distinctions. Additionally, prospective emotion reports that are based upon hypothetical situations, such as those used in the TEPS, are often made by accessing situation-specific schemas about how one should respond in a given-situation (Robinson & Clore, 2001). It is likely that such schemas differ greatly among patients, and that variable beliefs regarding how one should respond in a given situation could cause substantial variability in performance on prospective self-report measures. In contrast, we suspect that experimental paradigms that present a standard set of evocative stimuli that are then rated using a very concrete rating scale may be less susceptible to individual differences in cognitive processes that are not directly related to anhedonia and reward processing.
There is reason to suspect that ratings of emotional experience based upon verbal prompts may present challenges for many individuals with SZ. For example, we have previously reported that individuals with SZ abnormally discount the value of larger future rewards relative to smaller immediate rewards, and thought that this behavioral finding might reflect a compromised ability to represent the relative values of differing rewards (Heerey et al., 2007
). We also found that SZ patients made more inconsistent value-based preference judgments in a simple two-choice preference task, and made less fine grained distinctions in their preferences for emotional stimuli within the same valence category in comparison to CN (Strauss et al., in press
). Thus, the ability to distinguish the relative value of different rewards, or perhaps the ability to distinguish the enjoyment associated with different aspects of a reward experience, may draw upon cognitive and affective processes that are compromised in many individuals with SZ. It will remain for future work to examine the contribution of different cognitive abilities to TEPS performance.
In summary, while the conceptual distinction between reward anticipation and consumption is innovative and theoretically well-motivated, we were unable to replicate the major findings of previous studies using the TEPS (i.e., impaired anticipatory and intact consummatory pleasure) (Gard et al., 2007
; Favrod et al., 2009
; Chan et al., 2010
; Loas et al., 2010).. The advantages and limitations of online evocative testing, retrospective self-report, and prospective self-report measures of emotional experience are well-documented (Robinson & Clore, 2002
). Each holds its own distinctive pros and cons, and provides unique insight into the affective lives of individuals with SZ. Developing a more precise understanding of the nature of anhedonia and motivational impairment remains an important issue, and the apparent contradictions between the clinical and experimental laboratory literatures addressing this topic suggest that there is still important work to do in this area.